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@xxxxxxx>
---
drivers/md/md.c | 1
drivers/md/md.h | 8 +++
drivers/md/raid10.c | 122 ++++++++++++++++++++++++++++++++++-----------------
3 files changed, 90 insertions(+), 41 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 84796a5..3e8fcab 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -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;
diff --git a/drivers/md/md.h b/drivers/md/md.h
index a8d91fe..c797f5f 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -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;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 9838f08..7b3346a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -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 @@ retry:
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 @@ retry_write:
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;
}
@@ -1491,6 +1537,7 @@ 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
@@ -1503,6 +1550,11 @@ 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;
@@ -1522,11 +1574,6 @@ 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;
@@ -1534,17 +1581,6 @@ 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;
@@ -1555,7 +1591,19 @@ 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;
@@ -2099,6 +2147,7 @@ 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) {
@@ -2152,6 +2201,7 @@ 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;
@@ -3274,15 +3324,6 @@ 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;
}
@@ -3346,8 +3387,7 @@ 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;
--
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