On Thu, Jan 24, 2013 at 11:44:33AM -0500, Josef Bacik wrote:
> On Tue, Jan 08, 2013 at 07:49:21AM -0700, Liu Bo wrote:
> > During fsync, we put the changed parts(i.e. extent map) into the log tree,
> > and we ship these parts from a list of modified_extents to a local list
> > to process, of course, we must increment the refs of the extent maps to
> > avoid it from getting evicted from cache.
> >
> > The problem is
> > we don't hold the tree writer lock all the time of iterating the local list,
> > and it is possible that other threads hack in and delete the extent map from
> > the local list silently. So we'll end up with memory leak here.
> >
> > I hit this when testing xfstest 274 with mount options 'autodefrag,compress=zlib'.
> >
> > With this fix, the memory leak has gone away.
>
> This isn't going to work, we use the LOGGING flag to make sure the em isn't
> merged as well. Thanks,
A quick grep shows,
1 16 fs/btrfs/extent_map.h <<GLOBAL>>
#define EXTENT_FLAG_LOGGING 4
2 406 fs/btrfs/extent_map.c <<remove_extent_mapping>>
if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
3 3403 fs/btrfs/tree-log.c <<btrfs_log_changed_extents>>
set_bit(EXTENT_FLAG_LOGGING, &em->flags);
4 3413 fs/btrfs/tree-log.c <<btrfs_log_changed_extents>>
clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
how does the flag avoid merging em?
Seems we lost the check.
static int mergable_maps(struct extent_map *prev, struct extent_map *next)
{
if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
return 0;
/*
* don't merge compressed extents, we need to know their
* actual size
*/
if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
return 0;
...
}
thanks,
liubo
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