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nfs: use IS_ROOT not DCACHE_DISCONNECTED

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This check was added by Al Viro with
d9e80b7de91db05c1c4d2e5ebbfd70b3b3ba0e0f "nfs d_revalidate() is too
trigger-happy with d_drop()", with the explanation that we don't want to
remove the root of a disconnected tree, which will still be included on
the s_anon list.

But DCACHE_DISCONNECTED does *not* actually identify dentries that are
disconnected from the dentry tree or hashed on s_anon.  IS_ROOT() is the
way to do that.

Also add a comment from Al's commit to remind us why this check is
there.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
J. Bruce Fields 2013-10-15 17:03:16 -04:00 committed by Trond Myklebust
parent 9d3a2260f0
commit a3f432bfd0
1 changed files with 7 additions and 1 deletions
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8
fs/nfs/dir.c
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@ -1139,7 +1139,13 @@ out_zap_parent:
if (inode && S_ISDIR(inode->i_mode)) {
/* Purge readdir caches. */
nfs_zap_caches(inode);
if (dentry->d_flags & DCACHE_DISCONNECTED)
/*
* We can't d_drop the root of a disconnected tree:
* its d_hash is on the s_anon list and d_drop() would hide
* it from shrink_dcache_for_unmount(), leading to busy
* inodes on unmount and further oopses.
*/
if (IS_ROOT(dentry))
goto out_valid;
}
/* If we have submounts, don't unhash ! */