On Thu, May 09, 2019 at 09:05:39AM -0400, Brian Foster wrote: > On Wed, May 08, 2019 at 01:10:33PM -0700, Darrick J. Wong wrote: > > On Wed, May 08, 2019 at 02:28:09PM -0500, Eric Sandeen wrote: > > > If there are no attributes on the inode, don't go through the > > > cost of memory allocation and callling xfs_attr_get when we > > > already know we'll just get -ENOATTR. > > > > > > Reported-by: David Valin <dvalin@xxxxxxxxxx> > > > Suggested-by: Dave Chinner <david@xxxxxxxxxxxxx> > > > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> > > > --- > > > > > > diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c > > > index 8039e35147dd..b469b44e9e71 100644 > > > --- a/fs/xfs/xfs_acl.c > > > +++ b/fs/xfs/xfs_acl.c > > > @@ -132,6 +132,9 @@ xfs_get_acl(struct inode *inode, int type) > > > BUG(); > > > } > > > > > > + if (!xfs_inode_hasattr(ip)) > > > + return NULL; > > > > This isn't going to cause problems if someone's adding an ACL to the > > inode at the same time, right? > > > > I'm assuming that's the case since we only would load inodes when > > setting up a vfs inode but before any userspace can get its sticky > > fingers all over the inode, but it sure would be nice to know that > > for sure. :) > > > > Hmm, that's a good question. At first I was thinking it wouldn't matter, > but then I remembered the fairly recent issue around writing back an > empty leaf buffer on format conversion a bit too early. That has me > wondering if that would be an issue here as well. For example, suppose a > non-empty local format attr fork is being converted to extent format due > to a concurrent (and unrelated) xattr set. That involves > xfs_attr_shortform_to_leaf() -> xfs_bmap_local_to_extents_empty(), which > looks like it creates a transient empty fork state. Might > xfs_inode_hasattr() catch that as a false negative here? If so, that > would certainly be a problem if the existing xattr was the ACL the > caller happens to be interested in. It might be prudent to surround this > check with ILOCK_SHARED... <shrug> But xfs_inode_hasattr checks forkoff > 0, so as long as the shortform to leaf conversion doesn't zero forkoff we'd be fine, I think. AFAICT it doesn't...? --D > Brian > > > --D > > > > > + > > > /* > > > * If we have a cached ACLs value just return it, not need to > > > * go out to the disk. > > >
