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 create a raid1 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 is preemption, we just
have to hope that new devices are largely consistent with old devices.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
drivers/md/raid1.c | 77 ++++++++++++++++++++++++++++++++++++++--------------
1 files changed, 56 insertions(+), 21 deletions(-)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index c0d3ffb..fa4d840 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -523,6 +523,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
rdev = rcu_dereference(conf->mirrors[disk].rdev);
if (r1_bio->bios[disk] == IO_BLOCKED
|| rdev == NULL
+ || test_bit(Unmerged, &rdev->flags)
|| test_bit(Faulty, &rdev->flags))
continue;
if (!test_bit(In_sync, &rdev->flags) &&
@@ -614,6 +615,39 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
return best_disk;
}
+static int raid1_mergeable_bvec(struct request_queue *q,
+ struct bvec_merge_data *bvm,
+ struct bio_vec *biovec)
+{
+ struct mddev *mddev = q->queuedata;
+ struct r1conf *conf = mddev->private;
+ sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
+ int max = biovec->bv_len;
+
+ if (mddev->merge_check_needed) {
+ int disk;
+ rcu_read_lock();
+ for (disk = 0; disk < conf->raid_disks * 2; disk++) {
+ 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 = sector +
+ rdev->data_offset;
+ bvm->bi_bdev = rdev->bdev;
+ max = min(max, q->merge_bvec_fn(
+ q, bvm, biovec));
+ }
+ }
+ }
+ rcu_read_unlock();
+ }
+ return max;
+
+}
+
int md_raid1_congested(struct mddev *mddev, int bits)
{
struct r1conf *conf = mddev->private;
@@ -1015,7 +1049,8 @@ read_again:
break;
}
r1_bio->bios[i] = NULL;
- if (!rdev || test_bit(Faulty, &rdev->flags)) {
+ if (!rdev || test_bit(Faulty, &rdev->flags)
+ || test_bit(Unmerged, &rdev->flags)) {
if (i < conf->raid_disks)
set_bit(R1BIO_Degraded, &r1_bio->state);
continue;
@@ -1336,6 +1371,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
struct mirror_info *p;
int first = 0;
int last = conf->raid_disks - 1;
+ struct request_queue *q = bdev_get_queue(rdev->bdev);
if (mddev->recovery_disabled == conf->recovery_disabled)
return -EBUSY;
@@ -1343,23 +1379,17 @@ static int raid1_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;
+ }
+
for (mirror = first; mirror <= last; mirror++) {
p = conf->mirrors+mirror;
if (!p->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;
rdev->raid_disk = mirror;
@@ -1384,6 +1414,19 @@ static int raid1_add_disk(struct mddev *mddev, struct md_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);
+ lower_barrier(conf);
+ clear_bit(Unmerged, &rdev->flags);
+ }
md_integrity_add_rdev(rdev, mddev);
print_conf(conf);
return err;
@@ -2628,15 +2671,6 @@ static int run(struct mddev *mddev)
continue;
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, 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);
- }
}
mddev->degraded = 0;
@@ -2670,6 +2704,7 @@ static int run(struct mddev *mddev)
if (mddev->queue) {
mddev->queue->backing_dev_info.congested_fn = raid1_congested;
mddev->queue->backing_dev_info.congested_data = mddev;
+ blk_queue_merge_bvec(mddev->queue, raid1_mergeable_bvec);
}
return md_integrity_register(mddev);
}
--
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