[PATCH 0/7 v3] Push file_update_time() into .page_mkwrite

[PATCH 0/7 v3] Push file_update_time() into .page_mkwrite

[Jan Kara]

  Hello,

  to provide reliable support for filesystem freezing, filesystems need to have
complete control over when metadata is changed. In particular,
file_update_time() calls from page fault code make it impossible for
filesystems to prevent inodes from being dirtied while the filesystem is
frozen.

To fix the issue, this patch set changes page fault code to call
file_update_time() only when ->page_mkwrite() callback is not provided. If the
callback is provided, it is the responsibility of the filesystem to perform
update of i_mtime / i_ctime if needed. We also push file_update_time() call
to all existing ->page_mkwrite() implementations if the time update does not
obviously happen by other means. This is including __block_page_mkwrite() so
filesystems using it are handled. If you know your filesystem does not need
update of modification times in ->page_mkwrite() handler, please speak up and
I'll drop the patch for your filesystem.

As a side note, an alternative would be to remove calls of file_update_time()
from page fault code altogether and require all filesystems needing it to do
that in their ->page_mkwrite() implementation. That is certainly possible
although maybe slightly inefficient and would require auditting 100+
vm_operations_structs *shiver*.

Changes since v1:
* Dropped patches for filesystems which don't need them
* Added some acks
* Improved sysfs patch by Alex Elder's suggestion

Changes since v2:
* Dropped patches for more filesystems

Andrew, would you be willing to merge these patches via your tree? This seems
to be a final version.

								Honza

CC: Jaya Kumar <jayalk@intworks.biz>
CC: Sage Weil <sage@newdream.net>
CC: ceph-devel@vger.kernel.org
CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net
CC: Steven Whitehouse <swhiteho@redhat.com>
CC: cluster-devel@redhat.com
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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[PATCH 1/7] fb_defio: Push file_update_time() into fb_deferred_io_mkwrite()

[Jan Kara]

CC: Jaya Kumar <jayalk@intworks.biz>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 drivers/video/fb_defio.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index c27e153..7a09c06 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -104,6 +104,8 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
 	deferred framebuffer IO. then if userspace touches a page
 	again, we repeat the same scheme */
 
+	file_update_time(vma->vm_file);
+
 	/* protect against the workqueue changing the page list */
 	mutex_lock(&fbdefio->lock);
 
-- 
1.7.1

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[PATCH 2/7] fs: Push file_update_time() into __block_page_mkwrite()

[Jan Kara]

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/buffer.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 1a30db7..5294a33 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2300,6 +2300,12 @@ int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
 	loff_t size;
 	int ret;
 
+	/*
+	 * Update file times before taking page lock. We may end up failing the
+	 * fault so this update may be superfluous but who really cares...
+	 */
+	file_update_time(vma->vm_file);
+
 	lock_page(page);
 	size = i_size_read(inode);
 	if ((page->mapping != inode->i_mapping) ||
-- 
1.7.1

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[PATCH 3/7] ceph: Push file_update_time() into ceph_page_mkwrite()

[Jan Kara]

CC: Sage Weil <sage@newdream.net>
CC: ceph-devel@vger.kernel.org
Acked-by: Sage Weil <sage@newdream.net>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ceph/addr.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 173b1d2..12b139f 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1181,6 +1181,9 @@ static int ceph_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	loff_t size, len;
 	int ret;
 
+	/* Update time before taking page lock */
+	file_update_time(vma->vm_file);
+
 	size = i_size_read(inode);
 	if (off + PAGE_CACHE_SIZE <= size)
 		len = PAGE_CACHE_SIZE;
-- 
1.7.1

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[PATCH 4/7] 9p: Push file_update_time() into v9fs_vm_page_mkwrite()

[Jan Kara]

CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/9p/vfs_file.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index fc06fd2..dd6f7ee 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -610,6 +610,9 @@ v9fs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	p9_debug(P9_DEBUG_VFS, "page %p fid %lx\n",
 		 page, (unsigned long)filp->private_data);
 
+	/* Update file times before taking page lock */
+	file_update_time(filp);
+
 	v9inode = V9FS_I(inode);
 	/* make sure the cache has finished storing the page */
 	v9fs_fscache_wait_on_page_write(inode, page);
-- 
1.7.1

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[PATCH 5/7] gfs2: Push file_update_time() into gfs2_page_mkwrite()

[Jan Kara]

CC: Steven Whitehouse <swhiteho@redhat.com>
CC: cluster-devel@redhat.com
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/gfs2/file.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index c5fb359..1f03531 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -375,6 +375,9 @@ static int gfs2_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	 */
 	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
 
+	/* Update file times before taking page lock */
+	file_update_time(vma->vm_file);
+
 	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
 	ret = gfs2_glock_nq(&gh);
 	if (ret)
-- 
1.7.1

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[PATCH 6/7] sysfs: Push file_update_time() into bin_page_mkwrite()

[Jan Kara]

CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/sysfs/bin.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index a475983..614b2b5 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -228,6 +228,8 @@ static int bin_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	ret = 0;
 	if (bb->vm_ops->page_mkwrite)
 		ret = bb->vm_ops->page_mkwrite(vma, vmf);
+	else
+		file_update_time(file);
 
 	sysfs_put_active(attr_sd);
 	return ret;
-- 
1.7.1

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[PATCH 7/7] mm: Update file times from fault path only if .page_mkwrite is not set

[Jan Kara]

Filesystems wanting to properly support freezing need to have control
when file_update_time() is called. After pushing file_update_time()
to all relevant .page_mkwrite implementations we can just stop calling
file_update_time() when filesystem implements .page_mkwrite.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 mm/memory.c |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index fa2f04e..1dfe9a1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2621,6 +2621,9 @@ reuse:
 		if (!page_mkwrite) {
 			wait_on_page_locked(dirty_page);
 			set_page_dirty_balance(dirty_page, page_mkwrite);
+			/* file_update_time outside page_lock */
+			if (vma->vm_file)
+				file_update_time(vma->vm_file);
 		}
 		put_page(dirty_page);
 		if (page_mkwrite) {
@@ -2638,10 +2641,6 @@ reuse:
 			}
 		}
 
-		/* file_update_time outside page_lock */
-		if (vma->vm_file)
-			file_update_time(vma->vm_file);
-
 		return ret;
 	}
 
@@ -3310,12 +3309,13 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	if (dirty_page) {
 		struct address_space *mapping = page->mapping;
+		int dirtied = 0;
 
 		if (set_page_dirty(dirty_page))
-			page_mkwrite = 1;
+			dirtied = 1;
 		unlock_page(dirty_page);
 		put_page(dirty_page);
-		if (page_mkwrite && mapping) {
+		if ((dirtied || page_mkwrite) && mapping) {
 			/*
 			 * Some device drivers do not set page.mapping but still
 			 * dirty their pages
@@ -3324,7 +3324,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		}
 
 		/* file_update_time outside page_lock */
-		if (vma->vm_file)
+		if (vma->vm_file && !page_mkwrite)
 			file_update_time(vma->vm_file);
 	} else {
 		unlock_page(vmf.page);
-- 
1.7.1

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Re: [PATCH 0/7 v3] Push file_update_time() into .page_mkwrite

[Kamal Mostafa]

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On Mon, 2012-03-05 at 15:54 +0100, Jan Kara wrote:
> Hello,
> 
>   to provide reliable support for filesystem freezing, filesystems need to have
> complete control over when metadata is changed.  [...]

This patch set has been tested at Canonical along with the testing for
"[PATCH 00/19] Fix filesystem freezing deadlocks".

Please add the following endorsements for these patches (those actually
exercised by our test case):  1, 2, 6, 7

Tested-by: Kamal Mostafa <kamal@canonical.com>
Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com>
Tested-by: Dann Frazier <dann.frazier@canonical.com>
Tested-by: Massimo Morana <massimo.morana@canonical.com>
        
 -Kamal


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Re: [PATCH 0/7 v3] Push file_update_time() into .page_mkwrite

[Jan Kara]

On Sun 11-03-12 13:23:17, Kamal Mostafa wrote:
> On Mon, 2012-03-05 at 15:54 +0100, Jan Kara wrote:
> > Hello,
> > 
> >   to provide reliable support for filesystem freezing, filesystems need to have
> > complete control over when metadata is changed.  [...]
> 
> This patch set has been tested at Canonical along with the testing for
> "[PATCH 00/19] Fix filesystem freezing deadlocks".
> 
> Please add the following endorsements for these patches (those actually
> exercised by our test case):  1, 2, 6, 7
> 
> Tested-by: Kamal Mostafa <kamal@canonical.com>
> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com>
> Tested-by: Dann Frazier <dann.frazier@canonical.com>
> Tested-by: Massimo Morana <massimo.morana@canonical.com>
  Thanks for testing guys!

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

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