linux-kernel - Re: WARNING: at fs/inode.c:280 drop

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Message-ID: <20120925152731.52528dca@notabene.brown>
Date:	Tue, 25 Sep 2012 15:27:31 +1000
From:	NeilBrown <neilb@...e.de>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	"Myklebust, Trond" <Trond.Myklebust@...app.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: WARNING: at fs/inode.c:280 drop_nlink+0x31/0x33()

On Wed, 29 Aug 2012 15:16:41 -0700 Jeff Layton <jlayton@...hat.com> wrote:


> This stack trace comes from cifs, not nfs.

It's quite easy to trigger on NFS too.

 mount server:/path /mnt; exec 3>& /mnt/foo ; rm /mnt/foo; rm /mnt/.nfs* ;
 exec 3>&-

[634155.004438] WARNING:
at /home/abuild/rpmbuild/BUILD/kernel-desktop-3.5.0/lin [634155.004442]
Hardware name: Latitude E6510 [634155.004577]  crc_itu_t crc32c_intel
snd_hwdep snd_pcm snd_timer snd soundcor [634155.004609] Pid: 13402, comm:
bash Tainted: G        W    3.5.0-36-desktop # [634155.004611] Call Trace:
[634155.004630]  [<ffffffff8100444a>] dump_trace+0xaa/0x2b0
[634155.004641]  [<ffffffff815a23dc>] dump_stack+0x69/0x6f
[634155.004653]  [<ffffffff81041a0b>] warn_slowpath_common+0x7b/0xc0
[634155.004662]  [<ffffffff811832e4>] drop_nlink+0x34/0x40
[634155.004687]  [<ffffffffa05bb6c3>] nfs_dentry_iput+0x33/0x70 [nfs]
[634155.004714]  [<ffffffff8118049e>] dput+0x12e/0x230
[634155.004726]  [<ffffffff8116b230>] __fput+0x170/0x230
[634155.004735]  [<ffffffff81167c0f>] filp_close+0x5f/0x90
[634155.004743]  [<ffffffff81167cd7>] sys_close+0x97/0x100
[634155.004754]  [<ffffffff815c3b39>] system_call_fastpath+0x16/0x1b
[634155.004767]  [<00007f2a73a0d110>] 0x7f2a73a0d10f

Is this suitable for -stable?  It seems like it is just a harmless warning.

NeilBrown


Subject: NFS: avoid warning from nfs_drop_nlink

If you remove a file which is open, NFS will 'silly-rename' it to a
hidden file.
If you then remove that hidden file, and then close the open file,
then nfs_dentry_iput will perform an extra drop_nlink().
Since 3.3-rc1, this has produced a warning.
The simplest way to suppress it is to use "nfs_drop_nlink" which
checks for i_nlink being zero.

Signed-off-by: NeilBrown <neilb@...e.de>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 627f108..268af03 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1174,7 +1174,7 @@ static void nfs_dentry_iput(struct dentry *dentry,
struct inode *inode) NFS_I(inode)->cache_validity |= NFS_INO_INVALID_DATA;
 
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
-		drop_nlink(inode);
+		nfs_drop_nlink(inode);
 		nfs_complete_unlink(dentry, inode);
 	}
 	iput(inode);

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