On Wed, Aug 7, 2019 at 9:16 AM Nikolay Borisov <nbori...@suse.com> wrote:
>
>
>
> On 6.08.19 г. 13:09 ч., Filipe Manana wrote:
> > On Mon, Aug 5, 2019 at 3:48 PM Nikolay Borisov <nbori...@suse.com> wrote:
>
> <snip>
>
> >> @@ -1371,23 +1376,39 @@ static noinline int run_delalloc_nocow(struct
> >> inode *inode,
> >>
> >> btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
> >>
> >> + /* Didn't find anything for our INO */
> >> if (found_key.objectid > ino)
> >> break;
> >> + /*
> >> + * Found a different inode or no extents for our file,
> >> + * goto next slot
> >
> > No. This does not mean that there are no extents for the file. If
> > there weren't any, we would break instead of iterating to the next
> > slot.
> > One example described at
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1d512cb77bdbda80f0dd0620a3b260d697fd581d
>
> I see, thanks for the pointer. How about the following :
>
> /*
> * Keep searching until we find an EXTENT ITEM or are
> sure
> * there are no more extents for this inode
>
> */
Yes, that's just fine.
Thanks.
>
> While it doesn't mention the race condition this check, coupled with the
> next one (where we break if type > EXTENT_DATA_KEY), it reflects reality
> close enough?
>
>
> >
> >> + */
> >> if (WARN_ON_ONCE(found_key.objectid < ino) ||
> >> found_key.type < BTRFS_EXTENT_DATA_KEY) {
> >> path->slots[0]++;
> >> goto next_slot;
> >> }
> >> +
> >> + /* Found key is not EXTENT_DATA_KEY or starts after req
> >> range */
> >> if (found_key.type > BTRFS_EXTENT_DATA_KEY ||
> >> found_key.offset > end)
> >> break;
> >>
> >> + /*
> >> + * If the found extent starts after requested offset, then
> >> + * adjust extent_end to be right before this extent begins
> >> + */
> >> if (found_key.offset > cur_offset) {
> >> extent_end = found_key.offset;
> >> extent_type = 0;
> >> goto out_check;
> >> }
> >>
> >> +
> >> + /*
> >> + * Found extent which begins before our range and has the
> >> + * potential to intersect it.
> >> + */
> >> fi = btrfs_item_ptr(leaf, path->slots[0],
> >> struct btrfs_file_extent_item);
> >> extent_type = btrfs_file_extent_type(leaf, fi);
> <snip>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
