[PATCH 00/24] Refactor sys_swapon

[PATCH 00/24] Refactor sys_swapon

[Cesar Eduardo Barros]

This patch series refactors the sys_swapon function.

sys_swapon is currently a very large function, with 313 lines (more than 
12 25-line screens), which can make it a bit hard to read. This patch 
series reduces this size by half, by extracting large chunks of related 
code to new helper functions.

One of these chunks of code was nearly identical to the part of 
sys_swapoff which is used in case of a failure return from 
try_to_unuse(), so this patch series also makes both share the same code.

As a side effect of all this refactoring, the compiled code gets a bit 
smaller:

    text	   data	    bss	    dec	    hex	filename
   14012	    944	    276	  15232	   3b80	mm/swapfile.o.before
   13941	    944	    276	  15161	   3b39	mm/swapfile.o.after

Lightly tested on a x86_64 VM.

  mm/swapfile.c |  360 +++++++++++++++++++++++++++----------------------
  1 files changed, 197 insertions(+), 163 deletions(-)

Cesar Eduardo Barros (24):
       sys_swapon: use vzalloc instead of vmalloc/memset
       sys_swapon: remove changelog from function comment
       sys_swapon: do not depend on "type" after allocation
       sys_swapon: separate swap_info allocation
       sys_swapon: simplify error return from swap_info allocation
       sys_swapon: simplify error flow in alloc_swap_info
       sys_swapon: remove initial value of name variable
       sys_swapon: move setting of error nearer use
       sys_swapon: remove did_down variable
       sys_swapon: remove bdev variable
       sys_swapon: do only cleanup in the cleanup blocks
       sys_swapon: use a single error label
       sys_swapon: separate bdev claim and inode lock
       sys_swapon: simplify error flow in claim_swapfile
       sys_swapon: move setting of swapfilepages near use
       sys_swapon: separate parsing of swapfile header
       sys_swapon: simplify error flow in read_swap_header
       sys_swapon: call swap_cgroup_swapon earlier
       sys_swapon: separate parsing of bad blocks and extents
       sys_swapon: simplify error flow in setup_swap_map_and_extents
       sys_swapon: remove nr_good_pages variable
       sys_swapon: move printk outside lock
       sys_swapoff: change order to match sys_swapon
       sys_swapon: separate final enabling of the swapfile

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com

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[PATCH 01/24] sys_swapon: use vzalloc instead of vmalloc/memset

[Cesar Eduardo Barros]

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 07a458d..69a1f90 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2047,13 +2047,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		goto bad_swap;
 
 	/* OK, set up the swap map and apply the bad block list */
-	swap_map = vmalloc(maxpages);
+	swap_map = vzalloc(maxpages);
 	if (!swap_map) {
 		error = -ENOMEM;
 		goto bad_swap;
 	}
 
-	memset(swap_map, 0, maxpages);
 	nr_good_pages = maxpages - 1;	/* omit header page */
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
-- 
1.7.4

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[PATCH 02/24] sys_swapon: remove changelog from function comment

[Cesar Eduardo Barros]

Changelogs belong in the git history instead of in the source code.

Also, "The swapon system call" is redundant with
"SYSCALL_DEFINE2(swapon, ...)".

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 69a1f90..0fcbdca 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1844,11 +1844,6 @@ static int __init max_swapfiles_check(void)
 late_initcall(max_swapfiles_check);
 #endif
 
-/*
- * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
- *
- * The swapon system call
- */
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
-- 
1.7.4

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[PATCH 03/24] sys_swapon: do not depend on "type" after allocation

[Cesar Eduardo Barros]

Within sys_swapon, after the swap_info entry has been allocated, we
always have type == p->type and swap_info[type] == p. Use this fact to
reduce the dependency on the "type" local variable within the function,
as a preparation to move the allocation of the swap_info entry to a
separate function.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0fcbdca..f0fc4c0 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1927,7 +1927,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	for (i = 0; i < nr_swapfiles; i++) {
 		struct swap_info_struct *q = swap_info[i];
 
-		if (i == type || !q->swap_file)
+		if (q == p || !q->swap_file)
 			continue;
 		if (mapping == q->swap_file->f_mapping)
 			goto bad_swap;
@@ -2062,7 +2062,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		}
 	}
 
-	error = swap_cgroup_swapon(type, maxpages);
+	error = swap_cgroup_swapon(p->type, maxpages);
 	if (error)
 		goto bad_swap;
 
@@ -2120,9 +2120,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	p->next = i;
 	if (prev < 0)
-		swap_list.head = swap_list.next = type;
+		swap_list.head = swap_list.next = p->type;
 	else
-		swap_info[prev]->next = type;
+		swap_info[prev]->next = p->type;
 	spin_unlock(&swap_lock);
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);
@@ -2136,7 +2136,7 @@ bad_swap:
 		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 	}
 	destroy_swap_extents(p);
-	swap_cgroup_swapoff(type);
+	swap_cgroup_swapoff(p->type);
 bad_swap_2:
 	spin_lock(&swap_lock);
 	p->swap_file = NULL;
-- 
1.7.4

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[PATCH 04/24] sys_swapon: separate swap_info allocation

[Cesar Eduardo Barros]

Move the swap_info allocation to its own function. Only code movement,
no functional changes.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   57 +++++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index f0fc4c0..837e40f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1844,33 +1844,15 @@ static int __init max_swapfiles_check(void)
 late_initcall(max_swapfiles_check);
 #endif
 
-SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+static struct swap_info_struct *alloc_swap_info(void)
 {
 	struct swap_info_struct *p;
-	char *name = NULL;
-	struct block_device *bdev = NULL;
-	struct file *swap_file = NULL;
-	struct address_space *mapping;
 	unsigned int type;
-	int i, prev;
 	int error;
-	union swap_header *swap_header;
-	unsigned int nr_good_pages;
-	int nr_extents = 0;
-	sector_t span;
-	unsigned long maxpages;
-	unsigned long swapfilepages;
-	unsigned char *swap_map = NULL;
-	struct page *page = NULL;
-	struct inode *inode = NULL;
-	int did_down = 0;
-
-	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
 	if (!p)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	spin_lock(&swap_lock);
 	for (type = 0; type < nr_swapfiles; type++) {
@@ -1906,6 +1888,41 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	p->next = -1;
 	spin_unlock(&swap_lock);
 
+	return p;
+
+out:
+	return ERR_PTR(error);
+}
+
+SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+{
+	struct swap_info_struct *p;
+	char *name = NULL;
+	struct block_device *bdev = NULL;
+	struct file *swap_file = NULL;
+	struct address_space *mapping;
+	int i, prev;
+	int error;
+	union swap_header *swap_header;
+	unsigned int nr_good_pages;
+	int nr_extents = 0;
+	sector_t span;
+	unsigned long maxpages;
+	unsigned long swapfilepages;
+	unsigned char *swap_map = NULL;
+	struct page *page = NULL;
+	struct inode *inode = NULL;
+	int did_down = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	p = alloc_swap_info();
+	if (IS_ERR(p)) {
+		error = PTR_ERR(p);
+		goto out;
+	}
+
 	name = getname(specialfile);
 	error = PTR_ERR(name);
 	if (IS_ERR(name)) {
-- 
1.7.4

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[PATCH 05/24] sys_swapon: simplify error return from swap_info allocation

[Cesar Eduardo Barros]

At this point in sys_swapon, there is nothing to free. Return directly
instead of jumping to the cleanup block at the end of the function.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 837e40f..be728e3 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1918,10 +1918,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		return -EPERM;
 
 	p = alloc_swap_info();
-	if (IS_ERR(p)) {
-		error = PTR_ERR(p);
-		goto out;
-	}
+	if (IS_ERR(p))
+		return PTR_ERR(p);
 
 	name = getname(specialfile);
 	error = PTR_ERR(name);
-- 
1.7.4

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[PATCH 06/24] sys_swapon: simplify error flow in alloc_swap_info

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index be728e3..5538c77 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1848,7 +1848,6 @@ static struct swap_info_struct *alloc_swap_info(void)
 {
 	struct swap_info_struct *p;
 	unsigned int type;
-	int error;
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
 	if (!p)
@@ -1859,11 +1858,10 @@ static struct swap_info_struct *alloc_swap_info(void)
 		if (!(swap_info[type]->flags & SWP_USED))
 			break;
 	}
-	error = -EPERM;
 	if (type >= MAX_SWAPFILES) {
 		spin_unlock(&swap_lock);
 		kfree(p);
-		goto out;
+		return ERR_PTR(-EPERM);
 	}
 	if (type >= nr_swapfiles) {
 		p->type = type;
@@ -1889,9 +1887,6 @@ static struct swap_info_struct *alloc_swap_info(void)
 	spin_unlock(&swap_lock);
 
 	return p;
-
-out:
-	return ERR_PTR(error);
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCH 07/24] sys_swapon: remove initial value of name variable

[Cesar Eduardo Barros]

Now there is nothing which jumps to the cleanup blocks before the name
variable is set. There is no need to set it initially to NULL anymore.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5538c77..e21602c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1892,7 +1892,7 @@ static struct swap_info_struct *alloc_swap_info(void)
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
-	char *name = NULL;
+	char *name;
 	struct block_device *bdev = NULL;
 	struct file *swap_file = NULL;
 	struct address_space *mapping;
-- 
1.7.4

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[PATCH 08/24] sys_swapon: move setting of error nearer use

[Cesar Eduardo Barros]

Move the setting of the error variable nearer the goto in a few places.

Avoids calling PTR_ERR() if not IS_ERR() in two places, and makes the
error condition more explicit in two other places.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index e21602c..340537d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1917,14 +1917,14 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		return PTR_ERR(p);
 
 	name = getname(specialfile);
-	error = PTR_ERR(name);
 	if (IS_ERR(name)) {
+		error = PTR_ERR(name);
 		name = NULL;
 		goto bad_swap_2;
 	}
 	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
-	error = PTR_ERR(swap_file);
 	if (IS_ERR(swap_file)) {
+		error = PTR_ERR(swap_file);
 		swap_file = NULL;
 		goto bad_swap_2;
 	}
@@ -1933,17 +1933,17 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	mapping = swap_file->f_mapping;
 	inode = mapping->host;
 
-	error = -EBUSY;
 	for (i = 0; i < nr_swapfiles; i++) {
 		struct swap_info_struct *q = swap_info[i];
 
 		if (q == p || !q->swap_file)
 			continue;
-		if (mapping == q->swap_file->f_mapping)
+		if (mapping == q->swap_file->f_mapping) {
+			error = -EBUSY;
 			goto bad_swap;
+		}
 	}
 
-	error = -EINVAL;
 	if (S_ISBLK(inode->i_mode)) {
 		bdev = I_BDEV(inode);
 		error = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL,
@@ -1968,6 +1968,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 			goto bad_swap;
 		}
 	} else {
+		error = -EINVAL;
 		goto bad_swap;
 	}
 
-- 
1.7.4

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[PATCH 09/24] sys_swapon: remove did_down variable

[Cesar Eduardo Barros]

Since mutex_lock(&inode->i_mutex) is called just after setting inode,
did_down is always equivalent to (inode && S_ISREG(inode->i_mode)).

Use this fact to remove the did_down variable.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 340537d..1baaddc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1907,7 +1907,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
-	int did_down = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -1962,7 +1961,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
 		mutex_lock(&inode->i_mutex);
-		did_down = 1;
 		if (IS_SWAPFILE(inode)) {
 			error = -EBUSY;
 			goto bad_swap;
@@ -2163,7 +2161,7 @@ out:
 	}
 	if (name)
 		putname(name);
-	if (did_down) {
+	if (inode && S_ISREG(inode->i_mode)) {
 		if (!error)
 			inode->i_flags |= S_SWAPFILE;
 		mutex_unlock(&inode->i_mutex);
-- 
1.7.4

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[PATCH 10/24] sys_swapon: remove bdev variable

[Cesar Eduardo Barros]

The bdev variable is always equivalent to (S_ISBLK(inode->i_mode) ?
p->bdev : NULL), as long as it being set is moved to a bit earlier. Use
this fact to remove the bdev variable.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1baaddc..58fa178 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1893,7 +1893,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
 	char *name;
-	struct block_device *bdev = NULL;
 	struct file *swap_file = NULL;
 	struct address_space *mapping;
 	int i, prev;
@@ -1944,19 +1943,19 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 
 	if (S_ISBLK(inode->i_mode)) {
-		bdev = I_BDEV(inode);
-		error = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL,
+		p->bdev = I_BDEV(inode);
+		error = blkdev_get(p->bdev,
+				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
 				   sys_swapon);
 		if (error < 0) {
-			bdev = NULL;
+			p->bdev = NULL;
 			error = -EINVAL;
 			goto bad_swap;
 		}
-		p->old_block_size = block_size(bdev);
-		error = set_blocksize(bdev, PAGE_SIZE);
+		p->old_block_size = block_size(p->bdev);
+		error = set_blocksize(p->bdev, PAGE_SIZE);
 		if (error < 0)
 			goto bad_swap;
-		p->bdev = bdev;
 		p->flags |= SWP_BLKDEV;
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
@@ -2140,9 +2139,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	error = 0;
 	goto out;
 bad_swap:
-	if (bdev) {
-		set_blocksize(bdev, p->old_block_size);
-		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+	if (S_ISBLK(inode->i_mode) && p->bdev) {
+		set_blocksize(p->bdev, p->old_block_size);
+		blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 	}
 	destroy_swap_extents(p);
 	swap_cgroup_swapoff(p->type);
-- 
1.7.4

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[PATCH 11/24] sys_swapon: do only cleanup in the cleanup blocks

[Cesar Eduardo Barros]

The only way error is 0 in the cleanup blocks is when the function is
returning successfully. In this case, the cleanup blocks were setting
S_SWAPFILE in the S_ISREG case. But this is not a cleanup.

Move the setting of S_SWAPFILE to just before the "goto out;" to make
this more clear. At this point, we do not need to test for inode because
it will never be NULL.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 58fa178..f122f4a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2136,6 +2136,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	atomic_inc(&proc_poll_event);
 	wake_up_interruptible(&proc_poll_wait);
 
+	if (S_ISREG(inode->i_mode))
+		inode->i_flags |= S_SWAPFILE;
 	error = 0;
 	goto out;
 bad_swap:
@@ -2160,11 +2162,8 @@ out:
 	}
 	if (name)
 		putname(name);
-	if (inode && S_ISREG(inode->i_mode)) {
-		if (!error)
-			inode->i_flags |= S_SWAPFILE;
+	if (inode && S_ISREG(inode->i_mode))
 		mutex_unlock(&inode->i_mutex);
-	}
 	return error;
 }
 
-- 
1.7.4

--
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[PATCH 12/24] sys_swapon: use a single error label

[Cesar Eduardo Barros]

sys_swapon currently has two error labels, bad_swap and bad_swap_2.
bad_swap does the same as bad_swap_2 plus destroy_swap_extents() and
swap_cgroup_swapoff(); both are noops in the places where bad_swap_2 is
jumped to. With a single extra test for inode (matching the one in the
S_ISREG case below), all the error paths in the function can go to
bad_swap.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index f122f4a..57eff7e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1918,13 +1918,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (IS_ERR(name)) {
 		error = PTR_ERR(name);
 		name = NULL;
-		goto bad_swap_2;
+		goto bad_swap;
 	}
 	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
 	if (IS_ERR(swap_file)) {
 		error = PTR_ERR(swap_file);
 		swap_file = NULL;
-		goto bad_swap_2;
+		goto bad_swap;
 	}
 
 	p->swap_file = swap_file;
@@ -2141,13 +2141,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	error = 0;
 	goto out;
 bad_swap:
-	if (S_ISBLK(inode->i_mode) && p->bdev) {
+	if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
 		set_blocksize(p->bdev, p->old_block_size);
 		blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 	}
 	destroy_swap_extents(p);
 	swap_cgroup_swapoff(p->type);
-bad_swap_2:
 	spin_lock(&swap_lock);
 	p->swap_file = NULL;
 	p->flags = 0;
-- 
1.7.4

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[PATCH 13/24] sys_swapon: separate bdev claim and inode lock

[Cesar Eduardo Barros]

Move the code which claims the bdev (S_ISBLK) or locks the inode
(S_ISREG) to a separate function. Only code movement, no functional
changes.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   64 ++++++++++++++++++++++++++++++++++----------------------
 1 files changed, 39 insertions(+), 25 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 57eff7e..db772e4 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1889,6 +1889,43 @@ static struct swap_info_struct *alloc_swap_info(void)
 	return p;
 }
 
+static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
+{
+	int error;
+
+	if (S_ISBLK(inode->i_mode)) {
+		p->bdev = I_BDEV(inode);
+		error = blkdev_get(p->bdev,
+				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
+				   sys_swapon);
+		if (error < 0) {
+			p->bdev = NULL;
+			error = -EINVAL;
+			goto bad_swap;
+		}
+		p->old_block_size = block_size(p->bdev);
+		error = set_blocksize(p->bdev, PAGE_SIZE);
+		if (error < 0)
+			goto bad_swap;
+		p->flags |= SWP_BLKDEV;
+	} else if (S_ISREG(inode->i_mode)) {
+		p->bdev = inode->i_sb->s_bdev;
+		mutex_lock(&inode->i_mutex);
+		if (IS_SWAPFILE(inode)) {
+			error = -EBUSY;
+			goto bad_swap;
+		}
+	} else {
+		error = -EINVAL;
+		goto bad_swap;
+	}
+
+	return 0;
+
+bad_swap:
+	return error;
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
@@ -1942,32 +1979,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		}
 	}
 
-	if (S_ISBLK(inode->i_mode)) {
-		p->bdev = I_BDEV(inode);
-		error = blkdev_get(p->bdev,
-				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
-				   sys_swapon);
-		if (error < 0) {
-			p->bdev = NULL;
-			error = -EINVAL;
-			goto bad_swap;
-		}
-		p->old_block_size = block_size(p->bdev);
-		error = set_blocksize(p->bdev, PAGE_SIZE);
-		if (error < 0)
-			goto bad_swap;
-		p->flags |= SWP_BLKDEV;
-	} else if (S_ISREG(inode->i_mode)) {
-		p->bdev = inode->i_sb->s_bdev;
-		mutex_lock(&inode->i_mutex);
-		if (IS_SWAPFILE(inode)) {
-			error = -EBUSY;
-			goto bad_swap;
-		}
-	} else {
-		error = -EINVAL;
+	error = claim_swapfile(p, inode);
+	if (unlikely(error))
 		goto bad_swap;
-	}
 
 	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
 
-- 
1.7.4

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[PATCH 14/24] sys_swapon: simplify error flow in claim_swapfile

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   20 ++++++--------------
 1 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index db772e4..f5fe484 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1900,30 +1900,22 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 				   sys_swapon);
 		if (error < 0) {
 			p->bdev = NULL;
-			error = -EINVAL;
-			goto bad_swap;
+			return -EINVAL;
 		}
 		p->old_block_size = block_size(p->bdev);
 		error = set_blocksize(p->bdev, PAGE_SIZE);
 		if (error < 0)
-			goto bad_swap;
+			return error;
 		p->flags |= SWP_BLKDEV;
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
 		mutex_lock(&inode->i_mutex);
-		if (IS_SWAPFILE(inode)) {
-			error = -EBUSY;
-			goto bad_swap;
-		}
-	} else {
-		error = -EINVAL;
-		goto bad_swap;
-	}
+		if (IS_SWAPFILE(inode))
+			return -EBUSY;
+	} else
+		return -EINVAL;
 
 	return 0;
-
-bad_swap:
-	return error;
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCH 15/24] sys_swapon: move setting of swapfilepages near use

[Cesar Eduardo Barros]

There is no reason I can see to read inode->i_size long before it is
needed. Move its read to just before it is needed, to reduce the
variable lifetime.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index f5fe484..60c7784 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1975,8 +1975,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (unlikely(error))
 		goto bad_swap;
 
-	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
-
 	/*
 	 * Read the swap header.
 	 */
@@ -2045,6 +2043,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	error = -EINVAL;
 	if (!maxpages)
 		goto bad_swap;
+	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
 	if (swapfilepages && maxpages > swapfilepages) {
 		printk(KERN_WARNING
 		       "Swap area shorter than signature indicates\n");
-- 
1.7.4

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[PATCH 16/24] sys_swapon: separate parsing of swapfile header

[Cesar Eduardo Barros]

Move the code which parses and checks the swapfile header (except for
the bad block list) to a separate function. Only code movement, no
functional changes.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |  140 ++++++++++++++++++++++++++++++++-------------------------
 1 files changed, 78 insertions(+), 62 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 60c7784..314fb21 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1918,6 +1918,82 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 	return 0;
 }
 
+static unsigned long read_swap_header(struct swap_info_struct *p,
+					union swap_header *swap_header,
+					struct inode *inode)
+{
+	int i;
+	unsigned long maxpages;
+	unsigned long swapfilepages;
+
+	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
+		printk(KERN_ERR "Unable to find swap-space signature\n");
+		goto bad_swap;
+	}
+
+	/* swap partition endianess hack... */
+	if (swab32(swap_header->info.version) == 1) {
+		swab32s(&swap_header->info.version);
+		swab32s(&swap_header->info.last_page);
+		swab32s(&swap_header->info.nr_badpages);
+		for (i = 0; i < swap_header->info.nr_badpages; i++)
+			swab32s(&swap_header->info.badpages[i]);
+	}
+	/* Check the swap header's sub-version */
+	if (swap_header->info.version != 1) {
+		printk(KERN_WARNING
+		       "Unable to handle swap header version %d\n",
+		       swap_header->info.version);
+		goto bad_swap;
+	}
+
+	p->lowest_bit  = 1;
+	p->cluster_next = 1;
+	p->cluster_nr = 0;
+
+	/*
+	 * Find out how many pages are allowed for a single swap
+	 * device. There are two limiting factors: 1) the number of
+	 * bits for the swap offset in the swp_entry_t type and
+	 * 2) the number of bits in the a swap pte as defined by
+	 * the different architectures. In order to find the
+	 * largest possible bit mask a swap entry with swap type 0
+	 * and swap offset ~0UL is created, encoded to a swap pte,
+	 * decoded to a swp_entry_t again and finally the swap
+	 * offset is extracted. This will mask all the bits from
+	 * the initial ~0UL mask that can't be encoded in either
+	 * the swp_entry_t or the architecture definition of a
+	 * swap pte.
+	 */
+	maxpages = swp_offset(pte_to_swp_entry(
+			swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+	if (maxpages > swap_header->info.last_page) {
+		maxpages = swap_header->info.last_page + 1;
+		/* p->max is an unsigned int: don't overflow it */
+		if ((unsigned int)maxpages == 0)
+			maxpages = UINT_MAX;
+	}
+	p->highest_bit = maxpages - 1;
+
+	if (!maxpages)
+		goto bad_swap;
+	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
+	if (swapfilepages && maxpages > swapfilepages) {
+		printk(KERN_WARNING
+		       "Swap area shorter than signature indicates\n");
+		goto bad_swap;
+	}
+	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
+		goto bad_swap;
+	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
+		goto bad_swap;
+
+	return maxpages;
+
+bad_swap:
+	return 0;
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
@@ -1931,7 +2007,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int nr_extents = 0;
 	sector_t span;
 	unsigned long maxpages;
-	unsigned long swapfilepages;
 	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
@@ -1989,71 +2064,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	swap_header = kmap(page);
 
-	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
-		printk(KERN_ERR "Unable to find swap-space signature\n");
+	maxpages = read_swap_header(p, swap_header, inode);
+	if (unlikely(!maxpages)) {
 		error = -EINVAL;
 		goto bad_swap;
 	}
 
-	/* swap partition endianess hack... */
-	if (swab32(swap_header->info.version) == 1) {
-		swab32s(&swap_header->info.version);
-		swab32s(&swap_header->info.last_page);
-		swab32s(&swap_header->info.nr_badpages);
-		for (i = 0; i < swap_header->info.nr_badpages; i++)
-			swab32s(&swap_header->info.badpages[i]);
-	}
-	/* Check the swap header's sub-version */
-	if (swap_header->info.version != 1) {
-		printk(KERN_WARNING
-		       "Unable to handle swap header version %d\n",
-		       swap_header->info.version);
-		error = -EINVAL;
-		goto bad_swap;
-	}
-
-	p->lowest_bit  = 1;
-	p->cluster_next = 1;
-	p->cluster_nr = 0;
-
-	/*
-	 * Find out how many pages are allowed for a single swap
-	 * device. There are two limiting factors: 1) the number of
-	 * bits for the swap offset in the swp_entry_t type and
-	 * 2) the number of bits in the a swap pte as defined by
-	 * the different architectures. In order to find the
-	 * largest possible bit mask a swap entry with swap type 0
-	 * and swap offset ~0UL is created, encoded to a swap pte,
-	 * decoded to a swp_entry_t again and finally the swap
-	 * offset is extracted. This will mask all the bits from
-	 * the initial ~0UL mask that can't be encoded in either
-	 * the swp_entry_t or the architecture definition of a
-	 * swap pte.
-	 */
-	maxpages = swp_offset(pte_to_swp_entry(
-			swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
-	if (maxpages > swap_header->info.last_page) {
-		maxpages = swap_header->info.last_page + 1;
-		/* p->max is an unsigned int: don't overflow it */
-		if ((unsigned int)maxpages == 0)
-			maxpages = UINT_MAX;
-	}
-	p->highest_bit = maxpages - 1;
-
-	error = -EINVAL;
-	if (!maxpages)
-		goto bad_swap;
-	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
-	if (swapfilepages && maxpages > swapfilepages) {
-		printk(KERN_WARNING
-		       "Swap area shorter than signature indicates\n");
-		goto bad_swap;
-	}
-	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
-		goto bad_swap;
-	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
-		goto bad_swap;
-
 	/* OK, set up the swap map and apply the bad block list */
 	swap_map = vzalloc(maxpages);
 	if (!swap_map) {
-- 
1.7.4

--
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[PATCH 17/24] sys_swapon: simplify error flow in read_swap_header

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   15 ++++++---------
 1 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 314fb21..33c939d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1928,7 +1928,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 
 	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
 		printk(KERN_ERR "Unable to find swap-space signature\n");
-		goto bad_swap;
+		return 0;
 	}
 
 	/* swap partition endianess hack... */
@@ -1944,7 +1944,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 		printk(KERN_WARNING
 		       "Unable to handle swap header version %d\n",
 		       swap_header->info.version);
-		goto bad_swap;
+		return 0;
 	}
 
 	p->lowest_bit  = 1;
@@ -1976,22 +1976,19 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 	p->highest_bit = maxpages - 1;
 
 	if (!maxpages)
-		goto bad_swap;
+		return 0;
 	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
 	if (swapfilepages && maxpages > swapfilepages) {
 		printk(KERN_WARNING
 		       "Swap area shorter than signature indicates\n");
-		goto bad_swap;
+		return 0;
 	}
 	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
-		goto bad_swap;
+		return 0;
 	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
-		goto bad_swap;
+		return 0;
 
 	return maxpages;
-
-bad_swap:
-	return 0;
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCH 18/24] sys_swapon: call swap_cgroup_swapon earlier

[Cesar Eduardo Barros]

The call to swap_cgroup_swapon is in the middle of loading the swap map
and extents. As it only does memory allocation and does not depend on
the swapfile layout (map/extents), it can be called earlier (or later).

Move it to just after the allocation of swap_map, since it is
conceptually similar (allocates a map).

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 33c939d..6e9575b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2074,6 +2074,10 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		goto bad_swap;
 	}
 
+	error = swap_cgroup_swapon(p->type, maxpages);
+	if (error)
+		goto bad_swap;
+
 	nr_good_pages = maxpages - 1;	/* omit header page */
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
@@ -2088,10 +2092,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		}
 	}
 
-	error = swap_cgroup_swapon(p->type, maxpages);
-	if (error)
-		goto bad_swap;
-
 	if (nr_good_pages) {
 		swap_map[0] = SWAP_MAP_BAD;
 		p->max = maxpages;
-- 
1.7.4

--
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[PATCH 19/24] sys_swapon: separate parsing of bad blocks and extents

[Cesar Eduardo Barros]

Move the code which parses the bad block list and the extents to a
separate function. Only code movement, no functional changes.

This change uses the fact that, after the success path, nr_good_pages ==
p->pages.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   83 +++++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 54 insertions(+), 29 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 6e9575b..d91f8bb 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1991,6 +1991,54 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 	return maxpages;
 }
 
+static int setup_swap_map_and_extents(struct swap_info_struct *p,
+					union swap_header *swap_header,
+					unsigned char *swap_map,
+					unsigned long maxpages,
+					sector_t *span)
+{
+	int i;
+	int error;
+	unsigned int nr_good_pages;
+	int nr_extents;
+
+	nr_good_pages = maxpages - 1;	/* omit header page */
+
+	for (i = 0; i < swap_header->info.nr_badpages; i++) {
+		unsigned int page_nr = swap_header->info.badpages[i];
+		if (page_nr == 0 || page_nr > swap_header->info.last_page) {
+			error = -EINVAL;
+			goto bad_swap;
+		}
+		if (page_nr < maxpages) {
+			swap_map[page_nr] = SWAP_MAP_BAD;
+			nr_good_pages--;
+		}
+	}
+
+	if (nr_good_pages) {
+		swap_map[0] = SWAP_MAP_BAD;
+		p->max = maxpages;
+		p->pages = nr_good_pages;
+		nr_extents = setup_swap_extents(p, span);
+		if (nr_extents < 0) {
+			error = nr_extents;
+			goto bad_swap;
+		}
+		nr_good_pages = p->pages;
+	}
+	if (!nr_good_pages) {
+		printk(KERN_WARNING "Empty swap-file\n");
+		error = -EINVAL;
+		goto bad_swap;
+	}
+
+	return nr_extents;
+
+bad_swap:
+	return error;
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
@@ -2001,7 +2049,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int error;
 	union swap_header *swap_header;
 	unsigned int nr_good_pages;
-	int nr_extents = 0;
+	int nr_extents;
 	sector_t span;
 	unsigned long maxpages;
 	unsigned char *swap_map = NULL;
@@ -2078,36 +2126,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (error)
 		goto bad_swap;
 
-	nr_good_pages = maxpages - 1;	/* omit header page */
-
-	for (i = 0; i < swap_header->info.nr_badpages; i++) {
-		unsigned int page_nr = swap_header->info.badpages[i];
-		if (page_nr == 0 || page_nr > swap_header->info.last_page) {
-			error = -EINVAL;
-			goto bad_swap;
-		}
-		if (page_nr < maxpages) {
-			swap_map[page_nr] = SWAP_MAP_BAD;
-			nr_good_pages--;
-		}
-	}
-
-	if (nr_good_pages) {
-		swap_map[0] = SWAP_MAP_BAD;
-		p->max = maxpages;
-		p->pages = nr_good_pages;
-		nr_extents = setup_swap_extents(p, &span);
-		if (nr_extents < 0) {
-			error = nr_extents;
-			goto bad_swap;
-		}
-		nr_good_pages = p->pages;
-	}
-	if (!nr_good_pages) {
-		printk(KERN_WARNING "Empty swap-file\n");
-		error = -EINVAL;
+	nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
+		maxpages, &span);
+	if (unlikely(nr_extents < 0)) {
+		error = nr_extents;
 		goto bad_swap;
 	}
+	nr_good_pages = p->pages;
 
 	if (p->bdev) {
 		if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
-- 
1.7.4

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[PATCH 20/24] sys_swapon: simplify error flow in setup_swap_map_and_extents

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   19 +++++--------------
 1 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index d91f8bb..d2404ca 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1998,7 +1998,6 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 					sector_t *span)
 {
 	int i;
-	int error;
 	unsigned int nr_good_pages;
 	int nr_extents;
 
@@ -2006,10 +2005,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
 		unsigned int page_nr = swap_header->info.badpages[i];
-		if (page_nr == 0 || page_nr > swap_header->info.last_page) {
-			error = -EINVAL;
-			goto bad_swap;
-		}
+		if (page_nr == 0 || page_nr > swap_header->info.last_page)
+			return -EINVAL;
 		if (page_nr < maxpages) {
 			swap_map[page_nr] = SWAP_MAP_BAD;
 			nr_good_pages--;
@@ -2021,22 +2018,16 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 		p->max = maxpages;
 		p->pages = nr_good_pages;
 		nr_extents = setup_swap_extents(p, span);
-		if (nr_extents < 0) {
-			error = nr_extents;
-			goto bad_swap;
-		}
+		if (nr_extents < 0)
+			return nr_extents;
 		nr_good_pages = p->pages;
 	}
 	if (!nr_good_pages) {
 		printk(KERN_WARNING "Empty swap-file\n");
-		error = -EINVAL;
-		goto bad_swap;
+		return -EINVAL;
 	}
 
 	return nr_extents;
-
-bad_swap:
-	return error;
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCH 21/24] sys_swapon: remove nr_good_pages variable

[Cesar Eduardo Barros]

It still exists within setup_swap_map_and_extents(), but after it
nr_good_pages == p->pages.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index d2404ca..5ec7183 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2039,7 +2039,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int i, prev;
 	int error;
 	union swap_header *swap_header;
-	unsigned int nr_good_pages;
 	int nr_extents;
 	sector_t span;
 	unsigned long maxpages;
@@ -2123,7 +2122,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		error = nr_extents;
 		goto bad_swap;
 	}
-	nr_good_pages = p->pages;
 
 	if (p->bdev) {
 		if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
@@ -2143,12 +2141,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		p->prio = --least_priority;
 	p->swap_map = swap_map;
 	p->flags |= SWP_WRITEOK;
-	nr_swap_pages += nr_good_pages;
-	total_swap_pages += nr_good_pages;
+	nr_swap_pages += p->pages;
+	total_swap_pages += p->pages;
 
 	printk(KERN_INFO "Adding %uk swap on %s.  "
 			"Priority:%d extents:%d across:%lluk %s%s\n",
-		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
+		p->pages<<(PAGE_SHIFT-10), name, p->prio,
 		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
 		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
 		(p->flags & SWP_DISCARDABLE) ? "D" : "");
-- 
1.7.4

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[PATCH 22/24] sys_swapon: move printk outside lock

[Cesar Eduardo Barros]

The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(). To be
able to make both share the same code, move the printk() call in the
middle of it to just after it.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5ec7183..8f1b17b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2144,13 +2144,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	nr_swap_pages += p->pages;
 	total_swap_pages += p->pages;
 
-	printk(KERN_INFO "Adding %uk swap on %s.  "
-			"Priority:%d extents:%d across:%lluk %s%s\n",
-		p->pages<<(PAGE_SHIFT-10), name, p->prio,
-		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
-		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
-		(p->flags & SWP_DISCARDABLE) ? "D" : "");
-
 	/* insert swap space into swap_list: */
 	prev = -1;
 	for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
@@ -2164,6 +2157,14 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	else
 		swap_info[prev]->next = p->type;
 	spin_unlock(&swap_lock);
+
+	printk(KERN_INFO "Adding %uk swap on %s.  "
+			"Priority:%d extents:%d across:%lluk %s%s\n",
+		p->pages<<(PAGE_SHIFT-10), name, p->prio,
+		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
+		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
+		(p->flags & SWP_DISCARDABLE) ? "D" : "");
+
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);
 	wake_up_interruptible(&proc_poll_wait);
-- 
1.7.4

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[PATCH 23/24] sys_swapoff: change order to match sys_swapon

[Cesar Eduardo Barros]

The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(), except
for the order of the operations within the lock. Since the order should
not matter, arbitrarily change sys_swapoff to match sys_swapon, in
preparation to making both share the same code.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8f1b17b..deeb0b1 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1625,6 +1625,10 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 		spin_lock(&swap_lock);
 		if (p->prio < 0)
 			p->prio = --least_priority;
+		p->flags |= SWP_WRITEOK;
+		nr_swap_pages += p->pages;
+		total_swap_pages += p->pages;
+
 		prev = -1;
 		for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
 			if (p->prio >= swap_info[i]->prio)
@@ -1636,9 +1640,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 			swap_list.head = swap_list.next = type;
 		else
 			swap_info[prev]->next = type;
-		nr_swap_pages += p->pages;
-		total_swap_pages += p->pages;
-		p->flags |= SWP_WRITEOK;
 		spin_unlock(&swap_lock);
 		goto out_dput;
 	}
-- 
1.7.4

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[PATCH 24/24] sys_swapon: separate final enabling of the swapfile

[Cesar Eduardo Barros]

The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(). Move
this code to a separate function, and use it both in sys_swapon and
sys_swapoff.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   84 ++++++++++++++++++++++++++++----------------------------
 1 files changed, 42 insertions(+), 42 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index deeb0b1..100236b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1550,6 +1550,36 @@ bad_bmap:
 	goto out;
 }
 
+static void enable_swap_info(struct swap_info_struct *p, int prio,
+				unsigned char *swap_map)
+{
+	int i, prev;
+
+	spin_lock(&swap_lock);
+	if (prio >= 0)
+		p->prio = prio;
+	else
+		p->prio = --least_priority;
+	p->swap_map = swap_map;
+	p->flags |= SWP_WRITEOK;
+	nr_swap_pages += p->pages;
+	total_swap_pages += p->pages;
+
+	/* insert swap space into swap_list: */
+	prev = -1;
+	for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
+		if (p->prio >= swap_info[i]->prio)
+			break;
+		prev = i;
+	}
+	p->next = i;
+	if (prev < 0)
+		swap_list.head = swap_list.next = p->type;
+	else
+		swap_info[prev]->next = p->type;
+	spin_unlock(&swap_lock);
+}
+
 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 {
 	struct swap_info_struct *p = NULL;
@@ -1621,26 +1651,14 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	current->flags &= ~PF_OOM_ORIGIN;
 
 	if (err) {
+		/*
+		 * reading p->prio and p->swap_map outside the lock is
+		 * safe here because only sys_swapon and sys_swapoff
+		 * change them, and there can be no other sys_swapon or
+		 * sys_swapoff for this swap_info_struct at this point.
+		 */
 		/* re-insert swap space back into swap_list */
-		spin_lock(&swap_lock);
-		if (p->prio < 0)
-			p->prio = --least_priority;
-		p->flags |= SWP_WRITEOK;
-		nr_swap_pages += p->pages;
-		total_swap_pages += p->pages;
-
-		prev = -1;
-		for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
-			if (p->prio >= swap_info[i]->prio)
-				break;
-			prev = i;
-		}
-		p->next = i;
-		if (prev < 0)
-			swap_list.head = swap_list.next = type;
-		else
-			swap_info[prev]->next = type;
-		spin_unlock(&swap_lock);
+		enable_swap_info(p, p->prio, p->swap_map);
 		goto out_dput;
 	}
 
@@ -2037,7 +2055,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	char *name;
 	struct file *swap_file = NULL;
 	struct address_space *mapping;
-	int i, prev;
+	int i;
+	int prio;
 	int error;
 	union swap_header *swap_header;
 	int nr_extents;
@@ -2134,30 +2153,11 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 
 	mutex_lock(&swapon_mutex);
-	spin_lock(&swap_lock);
+	prio = -1;
 	if (swap_flags & SWAP_FLAG_PREFER)
-		p->prio =
+		prio =
 		  (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
-	else
-		p->prio = --least_priority;
-	p->swap_map = swap_map;
-	p->flags |= SWP_WRITEOK;
-	nr_swap_pages += p->pages;
-	total_swap_pages += p->pages;
-
-	/* insert swap space into swap_list: */
-	prev = -1;
-	for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
-		if (p->prio >= swap_info[i]->prio)
-			break;
-		prev = i;
-	}
-	p->next = i;
-	if (prev < 0)
-		swap_list.head = swap_list.next = p->type;
-	else
-		swap_info[prev]->next = p->type;
-	spin_unlock(&swap_lock);
+	enable_swap_info(p, prio, swap_map);
 
 	printk(KERN_INFO "Adding %uk swap on %s.  "
 			"Priority:%d extents:%d across:%lluk %s%s\n",
-- 
1.7.4

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Re: [PATCH 00/24] Refactor sys_swapon

[Eric B Munson]

[-- Attachment #1: Type: text/plain, Size: 1036 bytes --]

On Sat, 12 Feb 2011, Cesar Eduardo Barros wrote:

> This patch series refactors the sys_swapon function.
> 
> sys_swapon is currently a very large function, with 313 lines (more
> than 12 25-line screens), which can make it a bit hard to read. This
> patch series reduces this size by half, by extracting large chunks
> of related code to new helper functions.
> 
> One of these chunks of code was nearly identical to the part of
> sys_swapoff which is used in case of a failure return from
> try_to_unuse(), so this patch series also makes both share the same
> code.
> 
> As a side effect of all this refactoring, the compiled code gets a
> bit smaller:
> 
>    text	   data	    bss	    dec	    hex	filename
>   14012	    944	    276	  15232	   3b80	mm/swapfile.o.before
>   13941	    944	    276	  15161	   3b39	mm/swapfile.o.after
> 
> Lightly tested on a x86_64 VM.

I have been working on reviewing/testing this set and I cannot get it
to apply to Linus' tree, what is this set based on?

Thanks,
Eric

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 490 bytes --]

Re: [PATCH 00/24] Refactor sys_swapon

[Cesar Eduardo Barros]

Em 01-03-2011 15:20, Eric B Munson escreveu:
> On Sat, 12 Feb 2011, Cesar Eduardo Barros wrote:
>
>> This patch series refactors the sys_swapon function.
>
> I have been working on reviewing/testing this set and I cannot get it
> to apply to Linus' tree, what is this set based on?

According to the git tree from which I generated these patches, it was 
based on v2.6.38-rc4.

Commit 8074b26 (mm: fix refcounting in swapon) is what probably is 
causing you conflicts. I was planning to rebase and repost this patch 
series this weekend because of it.

I just did a quick rebase to Linus' current tree, and will post the 
whole set as a reply to this email. I have not even compile tested it, 
but the change is so small that, unless I made a typo when fixing the 
merge conflicts, it should work the same. The patches affected are 08 
(context only), 10, and 13.

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com

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[PATCHv2 00/24] Refactor sys_swapon

[Cesar Eduardo Barros]

This patch series refactors the sys_swapon function.

sys_swapon is currently a very large function, with 313 lines (more than
12 25-line screens), which can make it a bit hard to read. This patch
series reduces this size by half, by extracting large chunks of related
code to new helper functions.

One of these chunks of code was nearly identical to the part of
sys_swapoff which is used in case of a failure return from
try_to_unuse(), so this patch series also makes both share the same
code.

As a side effect of all this refactoring, the compiled code gets a bit
smaller (from v1 of this patch series):

   text       data        bss        dec        hex    filename
  14012        944        276      15232       3b80    mm/swapfile.o.before
  13941        944        276      15161       3b39    mm/swapfile.o.after

The v1 of this patch series was lightly tested on a x86_64 VM.

Changes from v1:
  Rebased from v2.6.38-rc4 to v2.6.38-rc7.

Cesar Eduardo Barros (24):
  sys_swapon: use vzalloc instead of vmalloc/memset
  sys_swapon: remove changelog from function comment
  sys_swapon: do not depend on "type" after allocation
  sys_swapon: separate swap_info allocation
  sys_swapon: simplify error return from swap_info allocation
  sys_swapon: simplify error flow in alloc_swap_info
  sys_swapon: remove initial value of name variable
  sys_swapon: move setting of error nearer use
  sys_swapon: remove did_down variable
  sys_swapon: remove bdev variable
  sys_swapon: do only cleanup in the cleanup blocks
  sys_swapon: use a single error label
  sys_swapon: separate bdev claim and inode lock
  sys_swapon: simplify error flow in claim_swapfile
  sys_swapon: move setting of swapfilepages near use
  sys_swapon: separate parsing of swapfile header
  sys_swapon: simplify error flow in read_swap_header
  sys_swapon: call swap_cgroup_swapon earlier
  sys_swapon: separate parsing of bad blocks and extents
  sys_swapon: simplify error flow in setup_swap_map_and_extents
  sys_swapon: remove nr_good_pages variable
  sys_swapon: move printk outside lock
  sys_swapoff: change order to match sys_swapon
  sys_swapon: separate final enabling of the swapfile

 mm/swapfile.c |  360 +++++++++++++++++++++++++++++++--------------------------
 1 files changed, 197 insertions(+), 163 deletions(-)

-- 
1.7.4

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[PATCHv2 01/24] sys_swapon: use vzalloc instead of vmalloc/memset

[Cesar Eduardo Barros]

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0341c57..3fe8913 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2047,13 +2047,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		goto bad_swap;
 
 	/* OK, set up the swap map and apply the bad block list */
-	swap_map = vmalloc(maxpages);
+	swap_map = vzalloc(maxpages);
 	if (!swap_map) {
 		error = -ENOMEM;
 		goto bad_swap;
 	}
 
-	memset(swap_map, 0, maxpages);
 	nr_good_pages = maxpages - 1;	/* omit header page */
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
-- 
1.7.4

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[PATCHv2 02/24] sys_swapon: remove changelog from function comment

[Cesar Eduardo Barros]

Changelogs belong in the git history instead of in the source code.

Also, "The swapon system call" is redundant with
"SYSCALL_DEFINE2(swapon, ...)".

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3fe8913..75ee39c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1844,11 +1844,6 @@ static int __init max_swapfiles_check(void)
 late_initcall(max_swapfiles_check);
 #endif
 
-/*
- * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
- *
- * The swapon system call
- */
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
-- 
1.7.4

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[PATCHv2 03/24] sys_swapon: do not depend on "type" after allocation

[Cesar Eduardo Barros]

Within sys_swapon, after the swap_info entry has been allocated, we
always have type == p->type and swap_info[type] == p. Use this fact to
reduce the dependency on the "type" local variable within the function,
as a preparation to move the allocation of the swap_info entry to a
separate function.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 75ee39c..3ef2d67 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1927,7 +1927,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	for (i = 0; i < nr_swapfiles; i++) {
 		struct swap_info_struct *q = swap_info[i];
 
-		if (i == type || !q->swap_file)
+		if (q == p || !q->swap_file)
 			continue;
 		if (mapping == q->swap_file->f_mapping)
 			goto bad_swap;
@@ -2062,7 +2062,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		}
 	}
 
-	error = swap_cgroup_swapon(type, maxpages);
+	error = swap_cgroup_swapon(p->type, maxpages);
 	if (error)
 		goto bad_swap;
 
@@ -2120,9 +2120,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	p->next = i;
 	if (prev < 0)
-		swap_list.head = swap_list.next = type;
+		swap_list.head = swap_list.next = p->type;
 	else
-		swap_info[prev]->next = type;
+		swap_info[prev]->next = p->type;
 	spin_unlock(&swap_lock);
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);
@@ -2136,7 +2136,7 @@ bad_swap:
 		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 	}
 	destroy_swap_extents(p);
-	swap_cgroup_swapoff(type);
+	swap_cgroup_swapoff(p->type);
 bad_swap_2:
 	spin_lock(&swap_lock);
 	p->swap_file = NULL;
-- 
1.7.4

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[PATCHv2 04/24] sys_swapon: separate swap_info allocation

[Cesar Eduardo Barros]

Move the swap_info allocation to its own function. Only code movement,
no functional changes.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   57 +++++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3ef2d67..91ca0f0 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1844,33 +1844,15 @@ static int __init max_swapfiles_check(void)
 late_initcall(max_swapfiles_check);
 #endif
 
-SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+static struct swap_info_struct *alloc_swap_info(void)
 {
 	struct swap_info_struct *p;
-	char *name = NULL;
-	struct block_device *bdev = NULL;
-	struct file *swap_file = NULL;
-	struct address_space *mapping;
 	unsigned int type;
-	int i, prev;
 	int error;
-	union swap_header *swap_header;
-	unsigned int nr_good_pages;
-	int nr_extents = 0;
-	sector_t span;
-	unsigned long maxpages;
-	unsigned long swapfilepages;
-	unsigned char *swap_map = NULL;
-	struct page *page = NULL;
-	struct inode *inode = NULL;
-	int did_down = 0;
-
-	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
 	if (!p)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	spin_lock(&swap_lock);
 	for (type = 0; type < nr_swapfiles; type++) {
@@ -1906,6 +1888,41 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	p->next = -1;
 	spin_unlock(&swap_lock);
 
+	return p;
+
+out:
+	return ERR_PTR(error);
+}
+
+SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
+{
+	struct swap_info_struct *p;
+	char *name = NULL;
+	struct block_device *bdev = NULL;
+	struct file *swap_file = NULL;
+	struct address_space *mapping;
+	int i, prev;
+	int error;
+	union swap_header *swap_header;
+	unsigned int nr_good_pages;
+	int nr_extents = 0;
+	sector_t span;
+	unsigned long maxpages;
+	unsigned long swapfilepages;
+	unsigned char *swap_map = NULL;
+	struct page *page = NULL;
+	struct inode *inode = NULL;
+	int did_down = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	p = alloc_swap_info();
+	if (IS_ERR(p)) {
+		error = PTR_ERR(p);
+		goto out;
+	}
+
 	name = getname(specialfile);
 	error = PTR_ERR(name);
 	if (IS_ERR(name)) {
-- 
1.7.4

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[PATCHv2 05/24] sys_swapon: simplify error return from swap_info allocation

[Cesar Eduardo Barros]

At this point in sys_swapon, there is nothing to free. Return directly
instead of jumping to the cleanup block at the end of the function.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 91ca0f0..8969b37 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1918,10 +1918,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		return -EPERM;
 
 	p = alloc_swap_info();
-	if (IS_ERR(p)) {
-		error = PTR_ERR(p);
-		goto out;
-	}
+	if (IS_ERR(p))
+		return PTR_ERR(p);
 
 	name = getname(specialfile);
 	error = PTR_ERR(name);
-- 
1.7.4

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[PATCHv2 06/24] sys_swapon: simplify error flow in alloc_swap_info

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8969b37..c97dc4b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1848,7 +1848,6 @@ static struct swap_info_struct *alloc_swap_info(void)
 {
 	struct swap_info_struct *p;
 	unsigned int type;
-	int error;
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
 	if (!p)
@@ -1859,11 +1858,10 @@ static struct swap_info_struct *alloc_swap_info(void)
 		if (!(swap_info[type]->flags & SWP_USED))
 			break;
 	}
-	error = -EPERM;
 	if (type >= MAX_SWAPFILES) {
 		spin_unlock(&swap_lock);
 		kfree(p);
-		goto out;
+		return ERR_PTR(-EPERM);
 	}
 	if (type >= nr_swapfiles) {
 		p->type = type;
@@ -1889,9 +1887,6 @@ static struct swap_info_struct *alloc_swap_info(void)
 	spin_unlock(&swap_lock);
 
 	return p;
-
-out:
-	return ERR_PTR(error);
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCHv2 07/24] sys_swapon: remove initial value of name variable

[Cesar Eduardo Barros]

Now there is nothing which jumps to the cleanup blocks before the name
variable is set. There is no need to set it initially to NULL anymore.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c97dc4b..8893c10 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1892,7 +1892,7 @@ static struct swap_info_struct *alloc_swap_info(void)
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
-	char *name = NULL;
+	char *name;
 	struct block_device *bdev = NULL;
 	struct file *swap_file = NULL;
 	struct address_space *mapping;
-- 
1.7.4

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[PATCHv2 08/24] sys_swapon: move setting of error nearer use

[Cesar Eduardo Barros]

Move the setting of the error variable nearer the goto in a few places.

Avoids calling PTR_ERR() if not IS_ERR() in two places, and makes the
error condition more explicit in two other places.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8893c10..55a50ef 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1917,14 +1917,14 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		return PTR_ERR(p);
 
 	name = getname(specialfile);
-	error = PTR_ERR(name);
 	if (IS_ERR(name)) {
+		error = PTR_ERR(name);
 		name = NULL;
 		goto bad_swap_2;
 	}
 	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
-	error = PTR_ERR(swap_file);
 	if (IS_ERR(swap_file)) {
+		error = PTR_ERR(swap_file);
 		swap_file = NULL;
 		goto bad_swap_2;
 	}
@@ -1933,17 +1933,17 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	mapping = swap_file->f_mapping;
 	inode = mapping->host;
 
-	error = -EBUSY;
 	for (i = 0; i < nr_swapfiles; i++) {
 		struct swap_info_struct *q = swap_info[i];
 
 		if (q == p || !q->swap_file)
 			continue;
-		if (mapping == q->swap_file->f_mapping)
+		if (mapping == q->swap_file->f_mapping) {
+			error = -EBUSY;
 			goto bad_swap;
+		}
 	}
 
-	error = -EINVAL;
 	if (S_ISBLK(inode->i_mode)) {
 		bdev = bdgrab(I_BDEV(inode));
 		error = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL,
@@ -1968,6 +1968,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 			goto bad_swap;
 		}
 	} else {
+		error = -EINVAL;
 		goto bad_swap;
 	}
 
-- 
1.7.4

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[PATCHv2 09/24] sys_swapon: remove did_down variable

[Cesar Eduardo Barros]

Since mutex_lock(&inode->i_mutex) is called just after setting inode,
did_down is always equivalent to (inode && S_ISREG(inode->i_mode)).

Use this fact to remove the did_down variable.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 55a50ef..c655389 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1907,7 +1907,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
-	int did_down = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -1962,7 +1961,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
 		mutex_lock(&inode->i_mutex);
-		did_down = 1;
 		if (IS_SWAPFILE(inode)) {
 			error = -EBUSY;
 			goto bad_swap;
@@ -2163,7 +2161,7 @@ out:
 	}
 	if (name)
 		putname(name);
-	if (did_down) {
+	if (inode && S_ISREG(inode->i_mode)) {
 		if (!error)
 			inode->i_flags |= S_SWAPFILE;
 		mutex_unlock(&inode->i_mutex);
-- 
1.7.4

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[PATCHv2 10/24] sys_swapon: remove bdev variable

[Cesar Eduardo Barros]

The bdev variable is always equivalent to (S_ISBLK(inode->i_mode) ?
p->bdev : NULL), as long as it being set is moved to a bit earlier. Use
this fact to remove the bdev variable.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c655389..bc00c1a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1893,7 +1893,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
 	char *name;
-	struct block_device *bdev = NULL;
 	struct file *swap_file = NULL;
 	struct address_space *mapping;
 	int i, prev;
@@ -1944,19 +1943,19 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 
 	if (S_ISBLK(inode->i_mode)) {
-		bdev = bdgrab(I_BDEV(inode));
-		error = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL,
+		p->bdev = bdgrab(I_BDEV(inode));
+		error = blkdev_get(p->bdev,
+				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
 				   sys_swapon);
 		if (error < 0) {
-			bdev = NULL;
+			p->bdev = NULL;
 			error = -EINVAL;
 			goto bad_swap;
 		}
-		p->old_block_size = block_size(bdev);
-		error = set_blocksize(bdev, PAGE_SIZE);
+		p->old_block_size = block_size(p->bdev);
+		error = set_blocksize(p->bdev, PAGE_SIZE);
 		if (error < 0)
 			goto bad_swap;
-		p->bdev = bdev;
 		p->flags |= SWP_BLKDEV;
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
@@ -2140,9 +2139,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	error = 0;
 	goto out;
 bad_swap:
-	if (bdev) {
-		set_blocksize(bdev, p->old_block_size);
-		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+	if (S_ISBLK(inode->i_mode) && p->bdev) {
+		set_blocksize(p->bdev, p->old_block_size);
+		blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 	}
 	destroy_swap_extents(p);
 	swap_cgroup_swapoff(p->type);
-- 
1.7.4

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[PATCHv2 11/24] sys_swapon: do only cleanup in the cleanup blocks

[Cesar Eduardo Barros]

The only way error is 0 in the cleanup blocks is when the function is
returning successfully. In this case, the cleanup blocks were setting
S_SWAPFILE in the S_ISREG case. But this is not a cleanup.

Move the setting of S_SWAPFILE to just before the "goto out;" to make
this more clear. At this point, we do not need to test for inode because
it will never be NULL.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index bc00c1a..ebc0307 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2136,6 +2136,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	atomic_inc(&proc_poll_event);
 	wake_up_interruptible(&proc_poll_wait);
 
+	if (S_ISREG(inode->i_mode))
+		inode->i_flags |= S_SWAPFILE;
 	error = 0;
 	goto out;
 bad_swap:
@@ -2160,11 +2162,8 @@ out:
 	}
 	if (name)
 		putname(name);
-	if (inode && S_ISREG(inode->i_mode)) {
-		if (!error)
-			inode->i_flags |= S_SWAPFILE;
+	if (inode && S_ISREG(inode->i_mode))
 		mutex_unlock(&inode->i_mutex);
-	}
 	return error;
 }
 
-- 
1.7.4

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[PATCHv2 12/24] sys_swapon: use a single error label

[Cesar Eduardo Barros]

sys_swapon currently has two error labels, bad_swap and bad_swap_2.
bad_swap does the same as bad_swap_2 plus destroy_swap_extents() and
swap_cgroup_swapoff(); both are noops in the places where bad_swap_2 is
jumped to. With a single extra test for inode (matching the one in the
S_ISREG case below), all the error paths in the function can go to
bad_swap.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index ebc0307..96be104 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1918,13 +1918,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (IS_ERR(name)) {
 		error = PTR_ERR(name);
 		name = NULL;
-		goto bad_swap_2;
+		goto bad_swap;
 	}
 	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
 	if (IS_ERR(swap_file)) {
 		error = PTR_ERR(swap_file);
 		swap_file = NULL;
-		goto bad_swap_2;
+		goto bad_swap;
 	}
 
 	p->swap_file = swap_file;
@@ -2141,13 +2141,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	error = 0;
 	goto out;
 bad_swap:
-	if (S_ISBLK(inode->i_mode) && p->bdev) {
+	if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
 		set_blocksize(p->bdev, p->old_block_size);
 		blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 	}
 	destroy_swap_extents(p);
 	swap_cgroup_swapoff(p->type);
-bad_swap_2:
 	spin_lock(&swap_lock);
 	p->swap_file = NULL;
 	p->flags = 0;
-- 
1.7.4

--
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[PATCHv2 13/24] sys_swapon: separate bdev claim and inode lock

[Cesar Eduardo Barros]

Move the code which claims the bdev (S_ISBLK) or locks the inode
(S_ISREG) to a separate function. Only code movement, no functional
changes.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   64 ++++++++++++++++++++++++++++++++++----------------------
 1 files changed, 39 insertions(+), 25 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 96be104..27faeec 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1889,6 +1889,43 @@ static struct swap_info_struct *alloc_swap_info(void)
 	return p;
 }
 
+static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
+{
+	int error;
+
+	if (S_ISBLK(inode->i_mode)) {
+		p->bdev = bdgrab(I_BDEV(inode));
+		error = blkdev_get(p->bdev,
+				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
+				   sys_swapon);
+		if (error < 0) {
+			p->bdev = NULL;
+			error = -EINVAL;
+			goto bad_swap;
+		}
+		p->old_block_size = block_size(p->bdev);
+		error = set_blocksize(p->bdev, PAGE_SIZE);
+		if (error < 0)
+			goto bad_swap;
+		p->flags |= SWP_BLKDEV;
+	} else if (S_ISREG(inode->i_mode)) {
+		p->bdev = inode->i_sb->s_bdev;
+		mutex_lock(&inode->i_mutex);
+		if (IS_SWAPFILE(inode)) {
+			error = -EBUSY;
+			goto bad_swap;
+		}
+	} else {
+		error = -EINVAL;
+		goto bad_swap;
+	}
+
+	return 0;
+
+bad_swap:
+	return error;
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
@@ -1942,32 +1979,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		}
 	}
 
-	if (S_ISBLK(inode->i_mode)) {
-		p->bdev = bdgrab(I_BDEV(inode));
-		error = blkdev_get(p->bdev,
-				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
-				   sys_swapon);
-		if (error < 0) {
-			p->bdev = NULL;
-			error = -EINVAL;
-			goto bad_swap;
-		}
-		p->old_block_size = block_size(p->bdev);
-		error = set_blocksize(p->bdev, PAGE_SIZE);
-		if (error < 0)
-			goto bad_swap;
-		p->flags |= SWP_BLKDEV;
-	} else if (S_ISREG(inode->i_mode)) {
-		p->bdev = inode->i_sb->s_bdev;
-		mutex_lock(&inode->i_mutex);
-		if (IS_SWAPFILE(inode)) {
-			error = -EBUSY;
-			goto bad_swap;
-		}
-	} else {
-		error = -EINVAL;
+	error = claim_swapfile(p, inode);
+	if (unlikely(error))
 		goto bad_swap;
-	}
 
 	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
 
-- 
1.7.4

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Re: [PATCHv2 13/24] sys_swapon: separate bdev claim and inode lock

[Eric B Munson]

[-- Attachment #1: Type: text/plain, Size: 2805 bytes --]

Nit pick below

On Tue, 01 Mar 2011, Cesar Eduardo Barros wrote:

> Move the code which claims the bdev (S_ISBLK) or locks the inode
> (S_ISREG) to a separate function. Only code movement, no functional
> changes.
> 
> Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
> ---
>  mm/swapfile.c |   64 ++++++++++++++++++++++++++++++++++----------------------
>  1 files changed, 39 insertions(+), 25 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 96be104..27faeec 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1889,6 +1889,43 @@ static struct swap_info_struct *alloc_swap_info(void)
>  	return p;
>  }
>  
> +static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
> +{
> +	int error;
> +
> +	if (S_ISBLK(inode->i_mode)) {
> +		p->bdev = bdgrab(I_BDEV(inode));
> +		error = blkdev_get(p->bdev,
> +				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
> +				   sys_swapon);
> +		if (error < 0) {
> +			p->bdev = NULL;
> +			error = -EINVAL;
> +			goto bad_swap;
> +		}
> +		p->old_block_size = block_size(p->bdev);
> +		error = set_blocksize(p->bdev, PAGE_SIZE);
> +		if (error < 0)
> +			goto bad_swap;
> +		p->flags |= SWP_BLKDEV;
> +	} else if (S_ISREG(inode->i_mode)) {
> +		p->bdev = inode->i_sb->s_bdev;
> +		mutex_lock(&inode->i_mutex);
> +		if (IS_SWAPFILE(inode)) {
> +			error = -EBUSY;
> +			goto bad_swap;
> +		}
> +	} else {
> +		error = -EINVAL;
> +		goto bad_swap;
> +	}
> +
> +	return 0;
> +
> +bad_swap:
> +	return error;
> +}
> +
>  SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>  {
>  	struct swap_info_struct *p;
> @@ -1942,32 +1979,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>  		}
>  	}
>  
> -	if (S_ISBLK(inode->i_mode)) {
> -		p->bdev = bdgrab(I_BDEV(inode));
> -		error = blkdev_get(p->bdev,
> -				   FMODE_READ | FMODE_WRITE | FMODE_EXCL,
> -				   sys_swapon);
> -		if (error < 0) {
> -			p->bdev = NULL;
> -			error = -EINVAL;
> -			goto bad_swap;
> -		}
> -		p->old_block_size = block_size(p->bdev);
> -		error = set_blocksize(p->bdev, PAGE_SIZE);
> -		if (error < 0)
> -			goto bad_swap;
> -		p->flags |= SWP_BLKDEV;
> -	} else if (S_ISREG(inode->i_mode)) {
> -		p->bdev = inode->i_sb->s_bdev;
> -		mutex_lock(&inode->i_mutex);
> -		if (IS_SWAPFILE(inode)) {
> -			error = -EBUSY;
> -			goto bad_swap;
> -		}
> -	} else {
> -		error = -EINVAL;
> +	error = claim_swapfile(p, inode);
> +	if (unlikely(error))

As a personal preference, I don't use likely/unlikley unless I have a profiler
telling me that the compiler got it wrong.  Just a suggestion.

>  		goto bad_swap;
> -	}
>  
>  	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
>  
> -- 
> 1.7.4
> 

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 490 bytes --]

Re: [PATCHv2 13/24] sys_swapon: separate bdev claim and inode lock

[Cesar Eduardo Barros]

Em 02-03-2011 18:40, Eric B Munson escreveu:
>> -	} else {
>> -		error = -EINVAL;
>> +	error = claim_swapfile(p, inode);
>> +	if (unlikely(error))
>
> As a personal preference, I don't use likely/unlikley unless I have a profiler
> telling me that the compiler got it wrong.  Just a suggestion.

I tend to use them for paths which should never happen in normal 
operation (error paths mostly). But yeah, I am probably still overusing 
them - who says the error path is not normal in some cases? Old habits 
die hard...

And I added more unlikely() calls than are visible in the patches. 
Remember that every IS_ERR() counts as a unlikely() too.

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com

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[PATCHv2 14/24] sys_swapon: simplify error flow in claim_swapfile

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   20 ++++++--------------
 1 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 27faeec..058cf1b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1900,30 +1900,22 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 				   sys_swapon);
 		if (error < 0) {
 			p->bdev = NULL;
-			error = -EINVAL;
-			goto bad_swap;
+			return -EINVAL;
 		}
 		p->old_block_size = block_size(p->bdev);
 		error = set_blocksize(p->bdev, PAGE_SIZE);
 		if (error < 0)
-			goto bad_swap;
+			return error;
 		p->flags |= SWP_BLKDEV;
 	} else if (S_ISREG(inode->i_mode)) {
 		p->bdev = inode->i_sb->s_bdev;
 		mutex_lock(&inode->i_mutex);
-		if (IS_SWAPFILE(inode)) {
-			error = -EBUSY;
-			goto bad_swap;
-		}
-	} else {
-		error = -EINVAL;
-		goto bad_swap;
-	}
+		if (IS_SWAPFILE(inode))
+			return -EBUSY;
+	} else
+		return -EINVAL;
 
 	return 0;
-
-bad_swap:
-	return error;
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCHv2 15/24] sys_swapon: move setting of swapfilepages near use

[Cesar Eduardo Barros]

There is no reason I can see to read inode->i_size long before it is
needed. Move its read to just before it is needed, to reduce the
variable lifetime.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 058cf1b..f3f413b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1975,8 +1975,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (unlikely(error))
 		goto bad_swap;
 
-	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
-
 	/*
 	 * Read the swap header.
 	 */
@@ -2045,6 +2043,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	error = -EINVAL;
 	if (!maxpages)
 		goto bad_swap;
+	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
 	if (swapfilepages && maxpages > swapfilepages) {
 		printk(KERN_WARNING
 		       "Swap area shorter than signature indicates\n");
-- 
1.7.4

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[PATCHv2 16/24] sys_swapon: separate parsing of swapfile header

[Cesar Eduardo Barros]

Move the code which parses and checks the swapfile header (except for
the bad block list) to a separate function. Only code movement, no
functional changes.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |  140 ++++++++++++++++++++++++++++++++-------------------------
 1 files changed, 78 insertions(+), 62 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index f3f413b..a56e6fe 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1918,6 +1918,82 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 	return 0;
 }
 
+static unsigned long read_swap_header(struct swap_info_struct *p,
+					union swap_header *swap_header,
+					struct inode *inode)
+{
+	int i;
+	unsigned long maxpages;
+	unsigned long swapfilepages;
+
+	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
+		printk(KERN_ERR "Unable to find swap-space signature\n");
+		goto bad_swap;
+	}
+
+	/* swap partition endianess hack... */
+	if (swab32(swap_header->info.version) == 1) {
+		swab32s(&swap_header->info.version);
+		swab32s(&swap_header->info.last_page);
+		swab32s(&swap_header->info.nr_badpages);
+		for (i = 0; i < swap_header->info.nr_badpages; i++)
+			swab32s(&swap_header->info.badpages[i]);
+	}
+	/* Check the swap header's sub-version */
+	if (swap_header->info.version != 1) {
+		printk(KERN_WARNING
+		       "Unable to handle swap header version %d\n",
+		       swap_header->info.version);
+		goto bad_swap;
+	}
+
+	p->lowest_bit  = 1;
+	p->cluster_next = 1;
+	p->cluster_nr = 0;
+
+	/*
+	 * Find out how many pages are allowed for a single swap
+	 * device. There are two limiting factors: 1) the number of
+	 * bits for the swap offset in the swp_entry_t type and
+	 * 2) the number of bits in the a swap pte as defined by
+	 * the different architectures. In order to find the
+	 * largest possible bit mask a swap entry with swap type 0
+	 * and swap offset ~0UL is created, encoded to a swap pte,
+	 * decoded to a swp_entry_t again and finally the swap
+	 * offset is extracted. This will mask all the bits from
+	 * the initial ~0UL mask that can't be encoded in either
+	 * the swp_entry_t or the architecture definition of a
+	 * swap pte.
+	 */
+	maxpages = swp_offset(pte_to_swp_entry(
+			swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+	if (maxpages > swap_header->info.last_page) {
+		maxpages = swap_header->info.last_page + 1;
+		/* p->max is an unsigned int: don't overflow it */
+		if ((unsigned int)maxpages == 0)
+			maxpages = UINT_MAX;
+	}
+	p->highest_bit = maxpages - 1;
+
+	if (!maxpages)
+		goto bad_swap;
+	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
+	if (swapfilepages && maxpages > swapfilepages) {
+		printk(KERN_WARNING
+		       "Swap area shorter than signature indicates\n");
+		goto bad_swap;
+	}
+	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
+		goto bad_swap;
+	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
+		goto bad_swap;
+
+	return maxpages;
+
+bad_swap:
+	return 0;
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
@@ -1931,7 +2007,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int nr_extents = 0;
 	sector_t span;
 	unsigned long maxpages;
-	unsigned long swapfilepages;
 	unsigned char *swap_map = NULL;
 	struct page *page = NULL;
 	struct inode *inode = NULL;
@@ -1989,71 +2064,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	swap_header = kmap(page);
 
-	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
-		printk(KERN_ERR "Unable to find swap-space signature\n");
+	maxpages = read_swap_header(p, swap_header, inode);
+	if (unlikely(!maxpages)) {
 		error = -EINVAL;
 		goto bad_swap;
 	}
 
-	/* swap partition endianess hack... */
-	if (swab32(swap_header->info.version) == 1) {
-		swab32s(&swap_header->info.version);
-		swab32s(&swap_header->info.last_page);
-		swab32s(&swap_header->info.nr_badpages);
-		for (i = 0; i < swap_header->info.nr_badpages; i++)
-			swab32s(&swap_header->info.badpages[i]);
-	}
-	/* Check the swap header's sub-version */
-	if (swap_header->info.version != 1) {
-		printk(KERN_WARNING
-		       "Unable to handle swap header version %d\n",
-		       swap_header->info.version);
-		error = -EINVAL;
-		goto bad_swap;
-	}
-
-	p->lowest_bit  = 1;
-	p->cluster_next = 1;
-	p->cluster_nr = 0;
-
-	/*
-	 * Find out how many pages are allowed for a single swap
-	 * device. There are two limiting factors: 1) the number of
-	 * bits for the swap offset in the swp_entry_t type and
-	 * 2) the number of bits in the a swap pte as defined by
-	 * the different architectures. In order to find the
-	 * largest possible bit mask a swap entry with swap type 0
-	 * and swap offset ~0UL is created, encoded to a swap pte,
-	 * decoded to a swp_entry_t again and finally the swap
-	 * offset is extracted. This will mask all the bits from
-	 * the initial ~0UL mask that can't be encoded in either
-	 * the swp_entry_t or the architecture definition of a
-	 * swap pte.
-	 */
-	maxpages = swp_offset(pte_to_swp_entry(
-			swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
-	if (maxpages > swap_header->info.last_page) {
-		maxpages = swap_header->info.last_page + 1;
-		/* p->max is an unsigned int: don't overflow it */
-		if ((unsigned int)maxpages == 0)
-			maxpages = UINT_MAX;
-	}
-	p->highest_bit = maxpages - 1;
-
-	error = -EINVAL;
-	if (!maxpages)
-		goto bad_swap;
-	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
-	if (swapfilepages && maxpages > swapfilepages) {
-		printk(KERN_WARNING
-		       "Swap area shorter than signature indicates\n");
-		goto bad_swap;
-	}
-	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
-		goto bad_swap;
-	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
-		goto bad_swap;
-
 	/* OK, set up the swap map and apply the bad block list */
 	swap_map = vzalloc(maxpages);
 	if (!swap_map) {
-- 
1.7.4

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[PATCHv2 17/24] sys_swapon: simplify error flow in read_swap_header

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   15 ++++++---------
 1 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index a56e6fe..13c13bd 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1928,7 +1928,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 
 	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
 		printk(KERN_ERR "Unable to find swap-space signature\n");
-		goto bad_swap;
+		return 0;
 	}
 
 	/* swap partition endianess hack... */
@@ -1944,7 +1944,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 		printk(KERN_WARNING
 		       "Unable to handle swap header version %d\n",
 		       swap_header->info.version);
-		goto bad_swap;
+		return 0;
 	}
 
 	p->lowest_bit  = 1;
@@ -1976,22 +1976,19 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 	p->highest_bit = maxpages - 1;
 
 	if (!maxpages)
-		goto bad_swap;
+		return 0;
 	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
 	if (swapfilepages && maxpages > swapfilepages) {
 		printk(KERN_WARNING
 		       "Swap area shorter than signature indicates\n");
-		goto bad_swap;
+		return 0;
 	}
 	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
-		goto bad_swap;
+		return 0;
 	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
-		goto bad_swap;
+		return 0;
 
 	return maxpages;
-
-bad_swap:
-	return 0;
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCHv2 18/24] sys_swapon: call swap_cgroup_swapon earlier

[Cesar Eduardo Barros]

The call to swap_cgroup_swapon is in the middle of loading the swap map
and extents. As it only does memory allocation and does not depend on
the swapfile layout (map/extents), it can be called earlier (or later).

Move it to just after the allocation of swap_map, since it is
conceptually similar (allocates a map).

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 13c13bd..7ac81fe 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2074,6 +2074,10 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		goto bad_swap;
 	}
 
+	error = swap_cgroup_swapon(p->type, maxpages);
+	if (error)
+		goto bad_swap;
+
 	nr_good_pages = maxpages - 1;	/* omit header page */
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
@@ -2088,10 +2092,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		}
 	}
 
-	error = swap_cgroup_swapon(p->type, maxpages);
-	if (error)
-		goto bad_swap;
-
 	if (nr_good_pages) {
 		swap_map[0] = SWAP_MAP_BAD;
 		p->max = maxpages;
-- 
1.7.4

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[PATCHv2 19/24] sys_swapon: separate parsing of bad blocks and extents

[Cesar Eduardo Barros]

Move the code which parses the bad block list and the extents to a
separate function. Only code movement, no functional changes.

This change uses the fact that, after the success path, nr_good_pages ==
p->pages.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   83 +++++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 54 insertions(+), 29 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7ac81fe..26eb84a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1991,6 +1991,54 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 	return maxpages;
 }
 
+static int setup_swap_map_and_extents(struct swap_info_struct *p,
+					union swap_header *swap_header,
+					unsigned char *swap_map,
+					unsigned long maxpages,
+					sector_t *span)
+{
+	int i;
+	int error;
+	unsigned int nr_good_pages;
+	int nr_extents;
+
+	nr_good_pages = maxpages - 1;	/* omit header page */
+
+	for (i = 0; i < swap_header->info.nr_badpages; i++) {
+		unsigned int page_nr = swap_header->info.badpages[i];
+		if (page_nr == 0 || page_nr > swap_header->info.last_page) {
+			error = -EINVAL;
+			goto bad_swap;
+		}
+		if (page_nr < maxpages) {
+			swap_map[page_nr] = SWAP_MAP_BAD;
+			nr_good_pages--;
+		}
+	}
+
+	if (nr_good_pages) {
+		swap_map[0] = SWAP_MAP_BAD;
+		p->max = maxpages;
+		p->pages = nr_good_pages;
+		nr_extents = setup_swap_extents(p, span);
+		if (nr_extents < 0) {
+			error = nr_extents;
+			goto bad_swap;
+		}
+		nr_good_pages = p->pages;
+	}
+	if (!nr_good_pages) {
+		printk(KERN_WARNING "Empty swap-file\n");
+		error = -EINVAL;
+		goto bad_swap;
+	}
+
+	return nr_extents;
+
+bad_swap:
+	return error;
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *p;
@@ -2001,7 +2049,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int error;
 	union swap_header *swap_header;
 	unsigned int nr_good_pages;
-	int nr_extents = 0;
+	int nr_extents;
 	sector_t span;
 	unsigned long maxpages;
 	unsigned char *swap_map = NULL;
@@ -2078,36 +2126,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (error)
 		goto bad_swap;
 
-	nr_good_pages = maxpages - 1;	/* omit header page */
-
-	for (i = 0; i < swap_header->info.nr_badpages; i++) {
-		unsigned int page_nr = swap_header->info.badpages[i];
-		if (page_nr == 0 || page_nr > swap_header->info.last_page) {
-			error = -EINVAL;
-			goto bad_swap;
-		}
-		if (page_nr < maxpages) {
-			swap_map[page_nr] = SWAP_MAP_BAD;
-			nr_good_pages--;
-		}
-	}
-
-	if (nr_good_pages) {
-		swap_map[0] = SWAP_MAP_BAD;
-		p->max = maxpages;
-		p->pages = nr_good_pages;
-		nr_extents = setup_swap_extents(p, &span);
-		if (nr_extents < 0) {
-			error = nr_extents;
-			goto bad_swap;
-		}
-		nr_good_pages = p->pages;
-	}
-	if (!nr_good_pages) {
-		printk(KERN_WARNING "Empty swap-file\n");
-		error = -EINVAL;
+	nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,
+		maxpages, &span);
+	if (unlikely(nr_extents < 0)) {
+		error = nr_extents;
 		goto bad_swap;
 	}
+	nr_good_pages = p->pages;
 
 	if (p->bdev) {
 		if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
-- 
1.7.4

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[PATCHv2 20/24] sys_swapon: simplify error flow in setup_swap_map_and_extents

[Cesar Eduardo Barros]

Since there is no cleanup to do, there is no reason to jump to a label.
Return directly instead.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   19 +++++--------------
 1 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 26eb84a..5f6df81 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1998,7 +1998,6 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 					sector_t *span)
 {
 	int i;
-	int error;
 	unsigned int nr_good_pages;
 	int nr_extents;
 
@@ -2006,10 +2005,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 
 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
 		unsigned int page_nr = swap_header->info.badpages[i];
-		if (page_nr == 0 || page_nr > swap_header->info.last_page) {
-			error = -EINVAL;
-			goto bad_swap;
-		}
+		if (page_nr == 0 || page_nr > swap_header->info.last_page)
+			return -EINVAL;
 		if (page_nr < maxpages) {
 			swap_map[page_nr] = SWAP_MAP_BAD;
 			nr_good_pages--;
@@ -2021,22 +2018,16 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 		p->max = maxpages;
 		p->pages = nr_good_pages;
 		nr_extents = setup_swap_extents(p, span);
-		if (nr_extents < 0) {
-			error = nr_extents;
-			goto bad_swap;
-		}
+		if (nr_extents < 0)
+			return nr_extents;
 		nr_good_pages = p->pages;
 	}
 	if (!nr_good_pages) {
 		printk(KERN_WARNING "Empty swap-file\n");
-		error = -EINVAL;
-		goto bad_swap;
+		return -EINVAL;
 	}
 
 	return nr_extents;
-
-bad_swap:
-	return error;
 }
 
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
-- 
1.7.4

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[PATCHv2 21/24] sys_swapon: remove nr_good_pages variable

[Cesar Eduardo Barros]

It still exists within setup_swap_map_and_extents(), but after it
nr_good_pages == p->pages.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5f6df81..369816d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2039,7 +2039,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int i, prev;
 	int error;
 	union swap_header *swap_header;
-	unsigned int nr_good_pages;
 	int nr_extents;
 	sector_t span;
 	unsigned long maxpages;
@@ -2123,7 +2122,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		error = nr_extents;
 		goto bad_swap;
 	}
-	nr_good_pages = p->pages;
 
 	if (p->bdev) {
 		if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
@@ -2143,12 +2141,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		p->prio = --least_priority;
 	p->swap_map = swap_map;
 	p->flags |= SWP_WRITEOK;
-	nr_swap_pages += nr_good_pages;
-	total_swap_pages += nr_good_pages;
+	nr_swap_pages += p->pages;
+	total_swap_pages += p->pages;
 
 	printk(KERN_INFO "Adding %uk swap on %s.  "
 			"Priority:%d extents:%d across:%lluk %s%s\n",
-		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
+		p->pages<<(PAGE_SHIFT-10), name, p->prio,
 		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
 		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
 		(p->flags & SWP_DISCARDABLE) ? "D" : "");
-- 
1.7.4

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[PATCHv2 22/24] sys_swapon: move printk outside lock

[Cesar Eduardo Barros]

The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(). To be
able to make both share the same code, move the printk() call in the
middle of it to just after it.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 369816d..33f9102 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2144,13 +2144,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	nr_swap_pages += p->pages;
 	total_swap_pages += p->pages;
 
-	printk(KERN_INFO "Adding %uk swap on %s.  "
-			"Priority:%d extents:%d across:%lluk %s%s\n",
-		p->pages<<(PAGE_SHIFT-10), name, p->prio,
-		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
-		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
-		(p->flags & SWP_DISCARDABLE) ? "D" : "");
-
 	/* insert swap space into swap_list: */
 	prev = -1;
 	for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
@@ -2164,6 +2157,14 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	else
 		swap_info[prev]->next = p->type;
 	spin_unlock(&swap_lock);
+
+	printk(KERN_INFO "Adding %uk swap on %s.  "
+			"Priority:%d extents:%d across:%lluk %s%s\n",
+		p->pages<<(PAGE_SHIFT-10), name, p->prio,
+		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
+		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
+		(p->flags & SWP_DISCARDABLE) ? "D" : "");
+
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);
 	wake_up_interruptible(&proc_poll_wait);
-- 
1.7.4

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[PATCHv2 23/24] sys_swapoff: change order to match sys_swapon

[Cesar Eduardo Barros]

The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(), except
for the order of the operations within the lock. Since the order should
not matter, arbitrarily change sys_swapoff to match sys_swapon, in
preparation to making both share the same code.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 33f9102..c9825aa 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1625,6 +1625,10 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 		spin_lock(&swap_lock);
 		if (p->prio < 0)
 			p->prio = --least_priority;
+		p->flags |= SWP_WRITEOK;
+		nr_swap_pages += p->pages;
+		total_swap_pages += p->pages;
+
 		prev = -1;
 		for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
 			if (p->prio >= swap_info[i]->prio)
@@ -1636,9 +1640,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 			swap_list.head = swap_list.next = type;
 		else
 			swap_info[prev]->next = type;
-		nr_swap_pages += p->pages;
-		total_swap_pages += p->pages;
-		p->flags |= SWP_WRITEOK;
 		spin_unlock(&swap_lock);
 		goto out_dput;
 	}
-- 
1.7.4

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[PATCHv2 24/24] sys_swapon: separate final enabling of the swapfile

[Cesar Eduardo Barros]

The block in sys_swapon which does the final adjustments to the
swap_info_struct and to swap_list is the same as the block which
re-inserts it again at sys_swapoff on failure of try_to_unuse(). Move
this code to a separate function, and use it both in sys_swapon and
sys_swapoff.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 mm/swapfile.c |   84 ++++++++++++++++++++++++++++----------------------------
 1 files changed, 42 insertions(+), 42 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c9825aa..49eb310 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1550,6 +1550,36 @@ bad_bmap:
 	goto out;
 }
 
+static void enable_swap_info(struct swap_info_struct *p, int prio,
+				unsigned char *swap_map)
+{
+	int i, prev;
+
+	spin_lock(&swap_lock);
+	if (prio >= 0)
+		p->prio = prio;
+	else
+		p->prio = --least_priority;
+	p->swap_map = swap_map;
+	p->flags |= SWP_WRITEOK;
+	nr_swap_pages += p->pages;
+	total_swap_pages += p->pages;
+
+	/* insert swap space into swap_list: */
+	prev = -1;
+	for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
+		if (p->prio >= swap_info[i]->prio)
+			break;
+		prev = i;
+	}
+	p->next = i;
+	if (prev < 0)
+		swap_list.head = swap_list.next = p->type;
+	else
+		swap_info[prev]->next = p->type;
+	spin_unlock(&swap_lock);
+}
+
 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 {
 	struct swap_info_struct *p = NULL;
@@ -1621,26 +1651,14 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	current->flags &= ~PF_OOM_ORIGIN;
 
 	if (err) {
+		/*
+		 * reading p->prio and p->swap_map outside the lock is
+		 * safe here because only sys_swapon and sys_swapoff
+		 * change them, and there can be no other sys_swapon or
+		 * sys_swapoff for this swap_info_struct at this point.
+		 */
 		/* re-insert swap space back into swap_list */
-		spin_lock(&swap_lock);
-		if (p->prio < 0)
-			p->prio = --least_priority;
-		p->flags |= SWP_WRITEOK;
-		nr_swap_pages += p->pages;
-		total_swap_pages += p->pages;
-
-		prev = -1;
-		for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
-			if (p->prio >= swap_info[i]->prio)
-				break;
-			prev = i;
-		}
-		p->next = i;
-		if (prev < 0)
-			swap_list.head = swap_list.next = type;
-		else
-			swap_info[prev]->next = type;
-		spin_unlock(&swap_lock);
+		enable_swap_info(p, p->prio, p->swap_map);
 		goto out_dput;
 	}
 
@@ -2037,7 +2055,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	char *name;
 	struct file *swap_file = NULL;
 	struct address_space *mapping;
-	int i, prev;
+	int i;
+	int prio;
 	int error;
 	union swap_header *swap_header;
 	int nr_extents;
@@ -2134,30 +2153,11 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 
 	mutex_lock(&swapon_mutex);
-	spin_lock(&swap_lock);
+	prio = -1;
 	if (swap_flags & SWAP_FLAG_PREFER)
-		p->prio =
+		prio =
 		  (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
-	else
-		p->prio = --least_priority;
-	p->swap_map = swap_map;
-	p->flags |= SWP_WRITEOK;
-	nr_swap_pages += p->pages;
-	total_swap_pages += p->pages;
-
-	/* insert swap space into swap_list: */
-	prev = -1;
-	for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
-		if (p->prio >= swap_info[i]->prio)
-			break;
-		prev = i;
-	}
-	p->next = i;
-	if (prev < 0)
-		swap_list.head = swap_list.next = p->type;
-	else
-		swap_info[prev]->next = p->type;
-	spin_unlock(&swap_lock);
+	enable_swap_info(p, prio, swap_map);
 
 	printk(KERN_INFO "Adding %uk swap on %s.  "
 			"Priority:%d extents:%d across:%lluk %s%s\n",
-- 
1.7.4

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Re: [PATCHv2 00/24] Refactor sys_swapon

[Eric B Munson]

[-- Attachment #1: Type: text/plain, Size: 1390 bytes --]

On Tue, 01 Mar 2011, Cesar Eduardo Barros wrote:

> This patch series refactors the sys_swapon function.
> 
> sys_swapon is currently a very large function, with 313 lines (more than
> 12 25-line screens), which can make it a bit hard to read. This patch
> series reduces this size by half, by extracting large chunks of related
> code to new helper functions.
> 
> One of these chunks of code was nearly identical to the part of
> sys_swapoff which is used in case of a failure return from
> try_to_unuse(), so this patch series also makes both share the same
> code.
> 
> As a side effect of all this refactoring, the compiled code gets a bit
> smaller (from v1 of this patch series):
> 
>    text       data        bss        dec        hex    filename
>   14012        944        276      15232       3b80    mm/swapfile.o.before
>   13941        944        276      15161       3b39    mm/swapfile.o.after
> 
> The v1 of this patch series was lightly tested on a x86_64 VM.
> 
> Changes from v1:
>   Rebased from v2.6.38-rc4 to v2.6.38-rc7.

I have tested this set on x86_64 by manually adding/removing swap files and
partitions.  Also I used the hugeadm program (fomr libhugetlbfs) to add
temporary swap files on disk and using ram disks.  All of this worked well.

Tested-by: Eric B Munson <emunson@mgebm.net>

This can be applied to the entire set.

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 490 bytes --]

Re: [PATCHv2 00/24] Refactor sys_swapon

[Eric B Munson]

[-- Attachment #1: Type: text/plain, Size: 1258 bytes --]

On Tue, 01 Mar 2011, Cesar Eduardo Barros wrote:

> This patch series refactors the sys_swapon function.
> 
> sys_swapon is currently a very large function, with 313 lines (more than
> 12 25-line screens), which can make it a bit hard to read. This patch
> series reduces this size by half, by extracting large chunks of related
> code to new helper functions.
> 
> One of these chunks of code was nearly identical to the part of
> sys_swapoff which is used in case of a failure return from
> try_to_unuse(), so this patch series also makes both share the same
> code.
> 
> As a side effect of all this refactoring, the compiled code gets a bit
> smaller (from v1 of this patch series):
> 
>    text       data        bss        dec        hex    filename
>   14012        944        276      15232       3b80    mm/swapfile.o.before
>   13941        944        276      15161       3b39    mm/swapfile.o.after
> 
> The v1 of this patch series was lightly tested on a x86_64 VM.
> 
> Changes from v1:
>   Rebased from v2.6.38-rc4 to v2.6.38-rc7.

Aside from my preference to avoid likely/unlikely unless necessary, I don't
see any problems with this series.

Acked-by: Eric B Munson <emunson@mgebm.net>

For the entire series

[-- Attachment #2: Digital signature --]
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Re: [PATCHv2 00/24] Refactor sys_swapon

[Eric B Munson]

[-- Attachment #1: Type: text/plain, Size: 1134 bytes --]

On Tue, 01 Mar 2011, Cesar Eduardo Barros wrote:

> This patch series refactors the sys_swapon function.
> 
> sys_swapon is currently a very large function, with 313 lines (more than
> 12 25-line screens), which can make it a bit hard to read. This patch
> series reduces this size by half, by extracting large chunks of related
> code to new helper functions.
> 
> One of these chunks of code was nearly identical to the part of
> sys_swapoff which is used in case of a failure return from
> try_to_unuse(), so this patch series also makes both share the same
> code.
> 
> As a side effect of all this refactoring, the compiled code gets a bit
> smaller (from v1 of this patch series):
> 
>    text       data        bss        dec        hex    filename
>   14012        944        276      15232       3b80    mm/swapfile.o.before
>   13941        944        276      15161       3b39    mm/swapfile.o.after
> 
> The v1 of this patch series was lightly tested on a x86_64 VM.

One more small suggestion, you should cc LKML on this series, as well as any
of the other emails suggested by get_maintainer.pl.

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Re: [PATCHv2 00/24] Refactor sys_swapon

[Cesar Eduardo Barros]

Em 03-03-2011 13:15, Eric B Munson escreveu:
> On Tue, 01 Mar 2011, Cesar Eduardo Barros wrote:
>
>> This patch series refactors the sys_swapon function.
>>
>> sys_swapon is currently a very large function, with 313 lines (more than
>> 12 25-line screens), which can make it a bit hard to read. This patch
>> series reduces this size by half, by extracting large chunks of related
>> code to new helper functions.
>>
>> One of these chunks of code was nearly identical to the part of
>> sys_swapoff which is used in case of a failure return from
>> try_to_unuse(), so this patch series also makes both share the same
>> code.
>>
>> As a side effect of all this refactoring, the compiled code gets a bit
>> smaller (from v1 of this patch series):
>>
>>     text       data        bss        dec        hex    filename
>>    14012        944        276      15232       3b80    mm/swapfile.o.before
>>    13941        944        276      15161       3b39    mm/swapfile.o.after
>>
>> The v1 of this patch series was lightly tested on a x86_64 VM.
>
> One more small suggestion, you should cc LKML on this series, as well as any
> of the other emails suggested by get_maintainer.pl.

Should I resend the whole patch series with the correct Cc:?

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com

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Re: [PATCHv2 00/24] Refactor sys_swapon

[Eric B Munson]

On Fri, Mar 4, 2011 at 5:54 PM, Cesar Eduardo Barros <cesarb@cesarb.net> wrote:
> Em 03-03-2011 13:15, Eric B Munson escreveu:
>>
>> On Tue, 01 Mar 2011, Cesar Eduardo Barros wrote:
>>
>>> This patch series refactors the sys_swapon function.
>>>
>>> sys_swapon is currently a very large function, with 313 lines (more than
>>> 12 25-line screens), which can make it a bit hard to read. This patch
>>> series reduces this size by half, by extracting large chunks of related
>>> code to new helper functions.
>>>
>>> One of these chunks of code was nearly identical to the part of
>>> sys_swapoff which is used in case of a failure return from
>>> try_to_unuse(), so this patch series also makes both share the same
>>> code.
>>>
>>> As a side effect of all this refactoring, the compiled code gets a bit
>>> smaller (from v1 of this patch series):
>>>
>>>    text       data        bss        dec        hex    filename
>>>   14012        944        276      15232       3b80
>>>  mm/swapfile.o.before
>>>   13941        944        276      15161       3b39
>>>  mm/swapfile.o.after
>>>
>>> The v1 of this patch series was lightly tested on a x86_64 VM.
>>
>> One more small suggestion, you should cc LKML on this series, as well as
>> any
>> of the other emails suggested by get_maintainer.pl.
>
> Should I resend the whole patch series with the correct Cc:?
>

I would and you can add my Tested-by: and Acked-by: to each patch as well.

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