On Fri 22-03-24 12:06:16, Andreas Dilger wrote:
> On Mar 21, 2024, at 10:26 AM, Jan Kara <jack@xxxxxxx> wrote:
> >
> > ext4_xattr_set_entry() creates new EA inodes while holding buffer lock
> > on the external xattr block. This is problematic as it nests all the
> > allocation locking (which acquires locks on other buffers) under the
> > buffer lock. This can even deadlock when the filesystem is corrupted and
> > e.g. quota file is setup to contain xattr block as data block. Move the
> > allocation of EA inode out of ext4_xattr_set_entry() into the callers.
>
> This looks like it will allocate a new inode for every setxattr called,
> even if the xattr is small and will likely fit inside the inode itself?
> This would seem to add a lot of extra overhead for the 99% of cases when
> an external inode is not needed.
This is not the case AFAICT. We call ext4_xattr_inode_lookup_create() only
in:
if (i->value && i->in_inode) {
so that means we've already decided we need to put the xattr value in the
EA inode. Note that ext4_xattr_set_handle() for smaller xattr value first
calls ext4_xattr_block_set() with i.in_inode == 0 and if that fails due to
ENOSPC, it sets i.in_inode = 1 and tries again.
So I think everything is fine.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
