On Thu, Jul 02, 2020 at 08:27:09AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> In commit 9851fd79bfb1, we added a slight amount of slack to the free
> space btrees being reconstructed so that the initial fix_freelist call
> (which is run against a totally empty AGFL) would never have to split
> either free space btree in order to populate the free list.
>
> The new btree bulk loading code in xfs_repair can re-create this
> situation because it can set the slack values to zero if the filesystem
> is very full. However, these days repair has the infrastructure needed
> to ensure that overestimations of the btree block counts end up on the
> AGFL or get freed back into the filesystem at the end of phase 5.
>
> Fix this problem by reserving extra blocks in the bnobt reservation, and
> checking that there are enough overages in the bnobt/cntbt fakeroots to
> populate the AGFL with the minimum number of blocks it needs to handle a
> split in the bno/cnt/rmap btrees.
>
> Note that we reserve blocks for the new bnobt/cntbt/AGFL at the very end
> of the reservation steps in phase 5, so the extra allocation should not
> cause repair to fail if it can't find blocks for btrees.
>
> Fixes: 9851fd79bfb1 ("repair: AGFL rebuild fails if btree split required")
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> repair/agbtree.c | 51 ++++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 44 insertions(+), 7 deletions(-)
>
>
> diff --git a/repair/agbtree.c b/repair/agbtree.c
> index de8015ec..9f64d54b 100644
> --- a/repair/agbtree.c
> +++ b/repair/agbtree.c
...
> @@ -268,16 +288,33 @@ _("Unable to compute free space by length btree geometry, error %d.\n"), -error)
> btr_cnt->bload.nr_blocks;
>
> /* We don't need any more blocks, so we're done. */
> - if (delta_bno >= 0 && delta_cnt >= 0) {
> + if (delta_bno >= 0 && delta_cnt >= 0 &&
> + delta_bno + delta_cnt >= agfl_goal) {
> *extra_blocks = delta_bno + delta_cnt;
> break;
> }
>
> /* Allocate however many more blocks we need this time. */
> - if (delta_bno < 0)
> + if (delta_bno < 0) {
> reserve_btblocks(sc->mp, agno, btr_bno, -delta_bno);
> - if (delta_cnt < 0)
> + delta_bno = 0;
> + }
> + if (delta_cnt < 0) {
> reserve_btblocks(sc->mp, agno, btr_cnt, -delta_cnt);
> + delta_cnt = 0;
> + }
> +
> + /*
> + * Try to fill the bnobt cursor with extra blocks to populate
> + * the AGFL. If we don't get all the blocks we want, stop
> + * trying to fill the AGFL because the AG is totally out of
> + * space.
> + */
> + agfl_wanted = agfl_goal - (delta_bno + delta_cnt);
> + if (agfl_wanted > 0 &&
> + agfl_wanted != reserve_agblocks(sc->mp, agno, btr_bno,
> + agfl_wanted))
> + agfl_goal = 0;
Nit: can we split off the function call so it's not embedded in the if
condition? With that tweak:
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
>
> /* Ok, now how many free space records do we have? */
> *nr_extents = count_bno_extents_blocks(agno, &num_freeblocks);
>
