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VFS: Fix the nfs sillyrename regression in kernel 2.6.38

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The new vfs locking scheme introduced in 2.6.38 breaks NFS sillyrename
because the latter relies on being able to determine the parent
directory of the dentry in the ->iput() callback in order to send the
appropriate unlink rpc call.

Looking at the code that cares about races with dput(), there doesn't
seem to be anything that specifically uses d_parent as a test for
whether or not there is a race:
  - __d_lookup_rcu(), __d_lookup() all test for d_hashed() after d_parent
  - shrink_dcache_for_umount() is safe since nothing else can rearrange
    the dentries in that super block.
  - have_submount(), select_parent() and d_genocide() can test for a
    deletion if we set the DCACHE_DISCONNECTED flag when the dentry
    is removed from the parent's d_subdirs list.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org (2.6.38, needs commit c826cb7dfc "dcache.c:
	create helper function for duplicated functionality" )
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Trond Myklebust 2011-03-15 13:36:43 -04:00 committed by Linus Torvalds
parent c826cb7dfc
commit c83ce989cb
1 changed files with 6 additions and 1 deletions
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7
fs/dcache.c
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@ -296,8 +296,12 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
__releases(parent->d_lock) __releases(parent->d_lock)
__releases(dentry->d_inode->i_lock) __releases(dentry->d_inode->i_lock)
{ {
dentry->d_parent = NULL;
list_del(&dentry->d_u.d_child); list_del(&dentry->d_u.d_child);
/*
* Inform try_to_ascend() that we are no longer attached to the
* dentry tree
*/
dentry->d_flags |= DCACHE_DISCONNECTED;
if (parent) if (parent)
spin_unlock(&parent->d_lock); spin_unlock(&parent->d_lock);
dentry_iput(dentry); dentry_iput(dentry);
@ -1030,6 +1034,7 @@ static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq
* or deletion * or deletion
*/ */
if (new != old->d_parent || if (new != old->d_parent ||
(old->d_flags & DCACHE_DISCONNECTED) ||
(!locked && read_seqretry(&rename_lock, seq))) { (!locked && read_seqretry(&rename_lock, seq))) {
spin_unlock(&new->d_lock); spin_unlock(&new->d_lock);
new = NULL; new = NULL;