[PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[David Howells]

Following bug was uncovered by compiling with '-W' flag:

  CC [M]  fs/afs/write.o
fs/afs/write.c: In function ‘afs_write_back_from_locked_page’:
fs/afs/write.c:398: warning: comparison of unsigned expression >= 0 is always true

Loop variable 'n' is unsigned, so wraps around happily as far as I can
see. Trival fix attached (compile tested only).

Signed-Off-By: Mika Kukkonen <mikukkon@iki.fi>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/write.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 67ae4db..28f3751 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -395,8 +395,9 @@ static int afs_write_back_from_locked_page(struct afs_writeback *wb,
 		if (n == 0)
 			goto no_more;
 		if (pages[0]->index != start) {
-			for (n--; n >= 0; n--)
-				put_page(pages[n]);
+			do {
+				put_page(pages[--n]);
+			} while (n > 0);
 			goto no_more;
 		}
 

[PATCH 2/2] AFS: Fix a couple of problems with unlinking AFS files

[David Howells]

Fix a couple of problems with unlinking AFS files.

 (1) The parent directory wasn't being updated properly between unlink() and
     the following lookup().

     It seems that, for some reason, invalidate_remote_inode() wasn't
     discarding the directory contents correctly, so this patch calls
     invalidate_inode_pages2() instead on non-regular files.

 (2) afs_vnode_deleted_remotely() should handle vnodes that don't have a
     source server recorded without oopsing.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/file.c  |    2 +-
 fs/afs/inode.c |   10 +++++++---
 fs/afs/super.c |    3 ++-
 fs/afs/vnode.c |   33 +++++++++++++++++++++------------
 4 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 3e25795..9c0e721 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -236,7 +236,7 @@ static void afs_invalidatepage(struct page *page, unsigned long offset)
 {
 	int ret = 1;
 
-	kenter("{%lu},%lu", page->index, offset);
+	_enter("{%lu},%lu", page->index, offset);
 
 	BUG_ON(!PageLocked(page));
 
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 515a5d1..47f5fed 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -209,11 +209,15 @@ bad_inode:
  */
 void afs_zap_data(struct afs_vnode *vnode)
 {
-	_enter("zap data {%x:%u}", vnode->fid.vid, vnode->fid.vnode);
+	_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
 
 	/* nuke all the non-dirty pages that aren't locked, mapped or being
-	 * written back */
-	invalidate_remote_inode(&vnode->vfs_inode);
+	 * written back in a regular file and completely discard the pages in a
+	 * directory or symlink */
+	if (S_ISREG(vnode->vfs_inode.i_mode))
+		invalidate_remote_inode(&vnode->vfs_inode);
+	else
+		invalidate_inode_pages2(vnode->vfs_inode.i_mapping);
 }
 
 /*
diff --git a/fs/afs/super.c b/fs/afs/super.c
index d24be33..422f532 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -488,6 +488,7 @@ static struct inode *afs_alloc_inode(struct super_block *sb)
 	vnode->flags		= 1 << AFS_VNODE_UNSET;
 	vnode->cb_promised	= false;
 
+	_leave(" = %p", &vnode->vfs_inode);
 	return &vnode->vfs_inode;
 }
 
@@ -498,7 +499,7 @@ static void afs_destroy_inode(struct inode *inode)
 {
 	struct afs_vnode *vnode = AFS_FS_I(inode);
 
-	_enter("{%lu}", inode->i_ino);
+	_enter("%p{%x:%u}", inode, vnode->fid.vid, vnode->fid.vnode);
 
 	_debug("DESTROY INODE %p", inode);
 
diff --git a/fs/afs/vnode.c b/fs/afs/vnode.c
index ec81466..bea8bd9 100644
--- a/fs/afs/vnode.c
+++ b/fs/afs/vnode.c
@@ -175,24 +175,33 @@ static void afs_vnode_deleted_remotely(struct afs_vnode *vnode)
 {
 	struct afs_server *server;
 
+	_enter("{%p}", vnode->server);
+
 	set_bit(AFS_VNODE_DELETED, &vnode->flags);
 
 	server = vnode->server;
-	if (vnode->cb_promised) {
-		spin_lock(&server->cb_lock);
+	if (server) {
 		if (vnode->cb_promised) {
-			rb_erase(&vnode->cb_promise, &server->cb_promises);
-			vnode->cb_promised = false;
+			spin_lock(&server->cb_lock);
+			if (vnode->cb_promised) {
+				rb_erase(&vnode->cb_promise,
+					 &server->cb_promises);
+				vnode->cb_promised = false;
+			}
+			spin_unlock(&server->cb_lock);
 		}
-		spin_unlock(&server->cb_lock);
-	}
 
-	spin_lock(&vnode->server->fs_lock);
-	rb_erase(&vnode->server_rb, &vnode->server->fs_vnodes);
-	spin_unlock(&vnode->server->fs_lock);
+		spin_lock(&server->fs_lock);
+		rb_erase(&vnode->server_rb, &server->fs_vnodes);
+		spin_unlock(&server->fs_lock);
 
-	vnode->server = NULL;
-	afs_put_server(server);
+		vnode->server = NULL;
+		afs_put_server(server);
+	} else {
+		ASSERT(!vnode->cb_promised);
+	}
+
+	_leave("");
 }
 
 /*
@@ -225,7 +234,7 @@ void afs_vnode_finalise_status_update(struct afs_vnode *vnode,
  */
 static void afs_vnode_status_update_failed(struct afs_vnode *vnode, int ret)
 {
-	_enter("%p,%d", vnode, ret);
+	_enter("{%x:%u},%d", vnode->fid.vid, vnode->fid.vnode, ret);
 
 	spin_lock(&vnode->lock);
 

Re: [PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[Andrew Morton]

On Thu, 10 May 2007 15:33:34 +0100
David Howells <dhowells@redhat.com> wrote:

> Following bug was uncovered by compiling with '-W' flag:

gcc -W finds a number of fairly scary bugs.

More than one would expect, given that it is recommended in
Documentation/SubmitChecklist, which everyone reads ;)

Re: [PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[David Howells]

Andrew Morton <akpm@linux-foundation.org> wrote:

> > Following bug was uncovered by compiling with '-W' flag:
> 
> gcc -W finds a number of fairly scary bugs.

Do you mean in my code specifically?  Or in the kernel in general?  As far as
I can tell -W only finds an eye-glazingly large quantity of 'unused parameter'
warnings in AFS and AF_RXRPC.

David

Re: [PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[David Howells]

Andrew Morton <akpm@linux-foundation.org> wrote:

> More than one would expect, given that it is recommended in
> Documentation/SubmitChecklist, which everyone reads ;)

Which states incorrectly:

| 22: Newly-added code has been compiled with `gcc -W'.  This will generate
|     lots of noise, but is good for finding bugs like "warning: comparison
|     between signed and unsigned".

-W does not imply -Wsign-compare, at least not on my gcc.

David

Re: [PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[Andrew Morton]

On Fri, 11 May 2007 10:49:23 +0100 David Howells <dhowells@redhat.com> wrote:

> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > > Following bug was uncovered by compiling with '-W' flag:
> > 
> > gcc -W finds a number of fairly scary bugs.
> 
> Do you mean in my code specifically?  Or in the kernel in general?

In general.

>  As far as
> I can tell -W only finds an eye-glazingly large quantity of 'unused parameter'
> warnings in AFS and AF_RXRPC.

Yes, it's a shame that there doesn't seem to be a fine-grained way of
turning on -W's useful bits.

Re: [PATCH 1/2] AFS: Fix interminable loop in afs_write_back_from_locked_page()

[David Howells]

Andrew Morton <akpm@linux-foundation.org> wrote:

> Yes, it's a shame that there doesn't seem to be a fine-grained way of
> turning on -W's useful bits.

You can turn off -W's undesirable bits.  For net/rxrpc/ and fs/afs/ at least,
adding:

	CFLAGS += -W -Wno-unused-parameter

to the Makefile generates no warnings.  Perhaps this should be added to the
master Makefile.

Adding -Wsign-compare finds some stuff that I will fix.  It also finds some
stuff in the main and the networking headers.  This is a really useful option
and found some tricky bugs in CacheFiles.  I would endorse adding this
generally too.

David