linux-kernel - [PATCH] NFSD: fix wrong mnt_writer count in rename (MMOTM 2007-11-10-19-05)

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Date:	Mon, 12 Nov 2007 20:15:11 -0500
From:	Erez Zadok <ezk@...sunysb.edu>
To:	bfields@...ldses.org, Dave Hansen <haveblue@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, nfs@...ts.sourceforge.net
Subject: [PATCH] NFSD: fix wrong mnt_writer count in rename (MMOTM 2007-11-10-19-05)

NFSD forgets to call mnt_drop_write after a successful rename.  Here's a
fix.  (Ah, the curse of a stackable file system developer: you have to debug
everyone else's too. :-)

One thing I wasn't sure is whether I could move the mnt_drop_write line a
little above, just after the call to vfs_rename.  If we can drop the ref
earlier, it could improve scalability/performance just a bit, no? (i.e.,
what are the ramifications of holding on to this mnt writer ref longer than
needed?)

Cheers,
Erez.

Signed-off-by: Erez Zadok <ezk@...sunysb.edu>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 7dfde65..47aec49 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1693,6 +1693,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 		if (!host_err)
 			host_err = nfsd_sync_dir(fdentry);
 	}
+	mnt_drop_write(ffhp->fh_export->ex_path.mnt);

  out_dput_new:
 	dput(ndentry);
-
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