Commit c83ce989 authored Mar 15, 2011 by Trond Myklebust Committed by Linus Torvalds Mar 15, 2011

VFS: Fix the nfs sillyrename regression in kernel 2.6.38



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 c826cb7d "dcache.c:
	create helper function for duplicated functionality" )
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c826cb7d

fs/dcache.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -296,8 +296,12 @@ static struct dentry d_kill(struct dentry dentry, struct dentry *parent)
		__releases(parent->d_lock)
		__releases(dentry->d_inode->i_lock)
		{
		dentry->d_parent = NULL;
		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)
		spin_unlock(&parent->d_lock);
		dentry_iput(dentry);
		@@ -1030,6 +1034,7 @@ static struct dentry try_to_ascend(struct dentry old, int locked, unsigned seq
		* or deletion
		*/
		if (new != old->d_parent \|\|
		(old->d_flags & DCACHE_DISCONNECTED) \|\|
		(!locked && read_seqretry(&rename_lock, seq))) {
		spin_unlock(&new->d_lock);
		new = NULL;

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