From: Erez Zadok <ezk@cs.sunysb.edu>

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?)

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/nfsd/vfs.c |    1 +
 1 file changed, 1 insertion(+)

diff -puN fs/nfsd/vfs.c~nfsd-fix-wrong-mnt_writer-count-in-rename fs/nfsd/vfs.c
--- a/fs/nfsd/vfs.c~nfsd-fix-wrong-mnt_writer-count-in-rename
+++ a/fs/nfsd/vfs.c
@@ -1688,6 +1688,7 @@ nfsd_rename(struct svc_rqst *rqstp, stru
 		if (!host_err)
 			host_err = nfsd_sync_dir(fdentry);
 	}
+	mnt_drop_write(ffhp->fh_export->ex_path.mnt);
 
  out_dput_new:
 	dput(ndentry);
_