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md/raid10: handle merge_bvec_fn in member devices.

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Currently we don't honour merge_bvec_fn in member devices so if there
is one, we force all requests to be single-page at most.
This is not ideal.

So enhance the raid10 merge_bvec_fn to check that function in children
as well.

This introduces a small problem.  There is no locking around calls
the ->merge_bvec_fn and subsequent calls to ->make_request.  So a
device added between these could end up getting a request which
violates its merge_bvec_fn.

Currently the best we can do is synchronize_sched().  This will work
providing no preemption happens.  If there is preemption, we just
have to hope that new devices are largely consistent with old devices.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2012-03-19 12:46:39 +11:00
parent ba13da47ff
commit 050b66152f
3 changed files with 90 additions and 41 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
drivers/md/md.c
View file

@ -5073,6 +5073,7 @@ static void md_clean(struct mddev *mddev)
mddev->changed = 0;
mddev->degraded = 0;
mddev->safemode = 0;
mddev->merge_check_needed = 0;
mddev->bitmap_info.offset = 0;
mddev->bitmap_info.default_offset = 0;
mddev->bitmap_info.chunksize = 0;

8
drivers/md/md.h
View file

@ -128,6 +128,10 @@ struct md_rdev {
enum flag_bits {
Faulty, /* device is known to have a fault */
In_sync, /* device is in_sync with rest of array */
Unmerged, /* device is being added to array and should
* be considerred for bvec_merge_fn but not
* yet for actual IO
*/
WriteMostly, /* Avoid reading if at all possible */
AutoDetected, /* added by auto-detect */
Blocked, /* An error occurred but has not yet
@ -345,6 +349,10 @@ struct mddev {
int degraded; /* whether md should consider
* adding a spare
*/
int merge_check_needed; /* at least one
* member device
* has a
* merge_bvec_fn */
atomic_t recovery_active; /* blocks scheduled, but not written */
wait_queue_head_t recovery_wait;

122
drivers/md/raid10.c
View file

@ -586,25 +586,68 @@ static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
* @biovec: the request that could be merged to it.
*
* Return amount of bytes we can accept at this offset
* If near_copies == raid_disk, there are no striping issues,
* but in that case, the function isn't called at all.
* This requires checking for end-of-chunk if near_copies != raid_disks,
* and for subordinate merge_bvec_fns if merge_check_needed.
*/
static int raid10_mergeable_bvec(struct request_queue *q,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
struct r10conf *conf = mddev->private;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
int max;
unsigned int chunk_sectors = mddev->chunk_sectors;
unsigned int bio_sectors = bvm->bi_size >> 9;
max = (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
if (max < 0) max = 0; /* bio_add cannot handle a negative return */
if (max <= biovec->bv_len && bio_sectors == 0)
return biovec->bv_len;
else
return max;
if (conf->near_copies < conf->raid_disks) {
max = (chunk_sectors - ((sector & (chunk_sectors - 1))
+ bio_sectors)) << 9;
if (max < 0)
/* bio_add cannot handle a negative return */
max = 0;
if (max <= biovec->bv_len && bio_sectors == 0)
return biovec->bv_len;
} else
max = biovec->bv_len;
if (mddev->merge_check_needed) {
struct r10bio r10_bio;
int s;
r10_bio.sector = sector;
raid10_find_phys(conf, &r10_bio);
rcu_read_lock();
for (s = 0; s < conf->copies; s++) {
int disk = r10_bio.devs[s].devnum;
struct md_rdev *rdev = rcu_dereference(
conf->mirrors[disk].rdev);
if (rdev && !test_bit(Faulty, &rdev->flags)) {
struct request_queue *q =
bdev_get_queue(rdev->bdev);
if (q->merge_bvec_fn) {
bvm->bi_sector = r10_bio.devs[s].addr
+ rdev->data_offset;
bvm->bi_bdev = rdev->bdev;
max = min(max, q->merge_bvec_fn(
q, bvm, biovec));
}
}
rdev = rcu_dereference(conf->mirrors[disk].replacement);
if (rdev && !test_bit(Faulty, &rdev->flags)) {
struct request_queue *q =
bdev_get_queue(rdev->bdev);
if (q->merge_bvec_fn) {
bvm->bi_sector = r10_bio.devs[s].addr
+ rdev->data_offset;
bvm->bi_bdev = rdev->bdev;
max = min(max, q->merge_bvec_fn(
q, bvm, biovec));
}
}
}
rcu_read_unlock();
}
return max;
}
/*
@ -668,11 +711,12 @@ static struct md_rdev *read_balance(struct r10conf *conf,
disk = r10_bio->devs[slot].devnum;
rdev = rcu_dereference(conf->mirrors[disk].replacement);
if (rdev == NULL || test_bit(Faulty, &rdev->flags) ||
test_bit(Unmerged, &rdev->flags) ||
r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (rdev == NULL)
continue;
if (test_bit(Faulty, &rdev->flags))
if (rdev == NULL ||
test_bit(Faulty, &rdev->flags) ||
test_bit(Unmerged, &rdev->flags))
continue;
if (!test_bit(In_sync, &rdev->flags) &&
r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
@ -1134,12 +1178,14 @@ static void make_request(struct mddev *mddev, struct bio * bio)
blocked_rdev = rrdev;
break;
}
if (rrdev && test_bit(Faulty, &rrdev->flags))
if (rrdev && (test_bit(Faulty, &rrdev->flags)
|| test_bit(Unmerged, &rrdev->flags)))
rrdev = NULL;
r10_bio->devs[i].bio = NULL;
r10_bio->devs[i].repl_bio = NULL;
if (!rdev || test_bit(Faulty, &rdev->flags)) {
if (!rdev || test_bit(Faulty, &rdev->flags) ||
test_bit(Unmerged, &rdev->flags)) {
set_bit(R10BIO_Degraded, &r10_bio->state);
continue;
}
@ -1490,6 +1536,7 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
int mirror;
int first = 0;
int last = conf->raid_disks - 1;
struct request_queue *q = bdev_get_queue(rdev->bdev);
if (mddev->recovery_cp < MaxSector)
/* only hot-add to in-sync arrays, as recovery is
@ -1502,6 +1549,11 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
if (rdev->raid_disk >= 0)
first = last = rdev->raid_disk;
if (q->merge_bvec_fn) {
set_bit(Unmerged, &rdev->flags);
mddev->merge_check_needed = 1;
}
if (rdev->saved_raid_disk >= first &&
conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
mirror = rdev->saved_raid_disk;
@ -1521,11 +1573,6 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
err = 0;
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
conf->fullsync = 1;
rcu_assign_pointer(p->replacement, rdev);
break;
@ -1533,17 +1580,6 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
/* as we don't honour merge_bvec_fn, we must
* never risk violating it, so limit
* ->max_segments to one lying with a single
* page, as a one page request is never in
* violation.
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
p->head_position = 0;
p->recovery_disabled = mddev->recovery_disabled - 1;
@ -1554,7 +1590,19 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
rcu_assign_pointer(p->rdev, rdev);
break;
}
if (err == 0 && test_bit(Unmerged, &rdev->flags)) {
/* Some requests might not have seen this new
* merge_bvec_fn. We must wait for them to complete
* before merging the device fully.
* First we make sure any code which has tested
* our function has submitted the request, then
* we wait for all outstanding requests to complete.
*/
synchronize_sched();
raise_barrier(conf, 0);
lower_barrier(conf);
clear_bit(Unmerged, &rdev->flags);
}
md_integrity_add_rdev(rdev, mddev);
print_conf(conf);
return err;
@ -2098,6 +2146,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
d = r10_bio->devs[sl].devnum;
rdev = rcu_dereference(conf->mirrors[d].rdev);
if (rdev &&
!test_bit(Unmerged, &rdev->flags) &&
test_bit(In_sync, &rdev->flags) &&
is_badblock(rdev, r10_bio->devs[sl].addr + sect, s,
&first_bad, &bad_sectors) == 0) {
@ -2151,6 +2200,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
d = r10_bio->devs[sl].devnum;
rdev = rcu_dereference(conf->mirrors[d].rdev);
if (!rdev ||
test_bit(Unmerged, &rdev->flags) ||
!test_bit(In_sync, &rdev->flags))
continue;
@ -3273,15 +3323,6 @@ static int run(struct mddev *mddev)
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
/* as we don't honour merge_bvec_fn, we must never risk
* violating it, so limit max_segments to 1 lying
* within a single page.
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
disk->head_position = 0;
}
@ -3345,8 +3386,7 @@ static int run(struct mddev *mddev)
mddev->queue->backing_dev_info.ra_pages = 2* stripe;
}
if (conf->near_copies < conf->raid_disks)
blk_queue_merge_bvec(mddev->queue, raid10_mergeable_bvec);
blk_queue_merge_bvec(mddev->queue, raid10_mergeable_bvec);
if (md_integrity_register(mddev))
goto out_free_conf;