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Subject[PATCH 3.12 61/88] make nfs_atomic_open() call d_drop() on all ->open_context() errors.
Date
From: Al Viro <viro@ZenIV.linux.org.uk>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit d20cb71dbf3487f24549ede1a8e2d67579b4632e upstream.

In "NFSv4: Move dentry instantiation into the NFSv4-specific atomic open code"
unconditional d_drop() after the ->open_context() had been removed. It had
been correct for success cases (there ->open_context() itself had been doing
dcache manipulations), but not for error ones. Only one of those (ENOENT)
got a compensatory d_drop() added in that commit, but in fact it should've
been done for all errors. As it is, the case of O_CREAT non-exclusive open
on a hashed negative dentry racing with e.g. symlink creation from another
client ended up with ->open_context() getting an error and proceeding to
call nfs_lookup(). On a hashed dentry, which would've instantly triggered
BUG_ON() in d_materialise_unique() (or, these days, its equivalent in
d_splice_alias()).

Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
fs/nfs/dir.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index cf6ede69a2e2..b9670301d7d3 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1483,9 +1483,9 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
err = PTR_ERR(inode);
trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
put_nfs_open_context(ctx);
+ d_drop(dentry);
switch (err) {
case -ENOENT:
- d_drop(dentry);
d_add(dentry, NULL);
break;
case -EISDIR:
--
2.9.1
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