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md/raid1: Don't use next_resync to determine how far resync has progressed

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next_resync is (approximately) the location for the next resync request.
However it does *not* reliably determine the earliest location
at which resync might be happening.
This is because resync requests can complete out of order, and
we only limit the number of current requests, not the distance
from the earliest pending request to the latest.

mddev->curr_resync_completed is a reliable indicator of the earliest
position at which resync could be happening.   It is updated less
frequently, but is actually reliable which is more important.

So use it to determine if a write request is before the region
being resynced and so safe from conflict.

This error can allow resync IO to interfere with normal IO which
could lead to data corruption. Hence: stable.

Fixes: 79ef3a8aa1
cc: stable@vger.kernel.org (v3.13+)
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2014-09-10 15:56:57 +10:00
parent 2f73d3c55d
commit 235549605e
1 changed files with 5 additions and 7 deletions
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12
drivers/md/raid1.c
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@ -875,12 +875,10 @@ static bool need_to_wait_for_sync(struct r1conf *conf, struct bio *bio)
if (conf->array_frozen || !bio)
wait = true;
else if (conf->barrier && bio_data_dir(bio) == WRITE) {
if (conf->next_resync < RESYNC_WINDOW_SECTORS)
wait = true;
else if ((conf->next_resync - RESYNC_WINDOW_SECTORS
>= bio_end_sector(bio)) ||
(conf->next_resync + NEXT_NORMALIO_DISTANCE
<= bio->bi_iter.bi_sector))
if ((conf->mddev->curr_resync_completed
>= bio_end_sector(bio)) ||
(conf->next_resync + NEXT_NORMALIO_DISTANCE
<= bio->bi_iter.bi_sector))
wait = false;
else
wait = true;
@ -918,7 +916,7 @@ static sector_t wait_barrier(struct r1conf *conf, struct bio *bio)
if (bio && bio_data_dir(bio) == WRITE) {
if (bio->bi_iter.bi_sector >=
conf->next_resync) {
conf->mddev->curr_resync_completed) {
if (conf->start_next_window == MaxSector)
conf->start_next_window =
conf->next_resync +