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md: deal with merge_bvec_fn in component devices better. 

If a component device has a merge_bvec_fn then as we never call it
we must ensure we never need to.  Currently this is done by setting
max_sector to 1 PAGE, however this does not stop a bio being created
with several sub-page iovecs that would violate the merge_bvec_fn.

So instead set max_segments to 1 and set the segment boundary to the
same as a page boundary to ensure there is only ever one single-page
segment of IO requested at a time.

This can particularly be an issue when 'xen' is used as it is
known to submit multiple small buffers in a single bio.

Signed-off-by: NeilBrown <neilb@suse.de>
Cc: stable@kernel.org
This commit is contained in:
NeilBrown 2010-03-08 16:44:38 +11:00
parent 25cf84cf37
commit 627a2d3c29
5 changed files with 60 additions and 41 deletions
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12
drivers/md/linear.c
View File

@ -172,12 +172,14 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
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_sector to one PAGE, as
* a one page request is never in violation.
* violating it, so limit max_segments to 1 lying within
* a single page.
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>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->array_sectors += rdev->sectors;
cnt++;

20
drivers/md/multipath.c
View File

@ -301,14 +301,16 @@ static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
rdev->data_offset << 9);
/* as we don't honour merge_bvec_fn, we must never risk
* violating it, so limit ->max_sector to one PAGE, as
* a one page request is never in violation.
* violating it, so limit ->max_segments to one, lying
* within a single page.
* (Note: it is very unlikely that a device with
* merge_bvec_fn will be involved in multipath.)
*/
if (q->merge_bvec_fn &&
queue_max_sectors(q) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>9);
if (q->merge_bvec_fn) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
conf->working_disks++;
mddev->degraded--;
@ -476,9 +478,11 @@ static int multipath_run (mddev_t *mddev)
/* as we don't honour merge_bvec_fn, we must never risk
* violating it, not that we ever expect a device with
* a merge_bvec_fn to be involved in multipath */
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>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);
}
if (!test_bit(Faulty, &rdev->flags))
conf->working_disks++;

13
drivers/md/raid0.c
View File

@ -176,14 +176,15 @@ static int create_strip_zones(mddev_t *mddev)
disk_stack_limits(mddev->gendisk, rdev1->bdev,
rdev1->data_offset << 9);
/* as we don't honour merge_bvec_fn, we must never risk
* violating it, so limit ->max_sector to one PAGE, as
* a one page request is never in violation.
* violating it, so limit ->max_segments to 1, lying within
* a single page.
*/
if (rdev1->bdev->bd_disk->queue->merge_bvec_fn &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>9);
if (rdev1->bdev->bd_disk->queue->merge_bvec_fn) {
blk_queue_max_segments(mddev->queue, 1);
blk_queue_segment_boundary(mddev->queue,
PAGE_CACHE_SIZE - 1);
}
if (!smallest || (rdev1->sectors < smallest->sectors))
smallest = rdev1;
cnt++;

28
drivers/md/raid1.c
View File

@ -1152,13 +1152,17 @@ static int raid1_add_disk(mddev_t *mddev, mdk_rdev_t *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_sector to one PAGE, as
* a one page request is never in violation.
/* 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 &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>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);
}
p->head_position = 0;
rdev->raid_disk = mirror;
@ -2098,12 +2102,14 @@ static int run(mddev_t *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_sector to one PAGE, as
* a one page request is never in violation.
* 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 &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>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);
}
}
mddev->degraded = 0;

28
drivers/md/raid10.c
View File

@ -1155,13 +1155,17 @@ static int raid10_add_disk(mddev_t *mddev, mdk_rdev_t *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_sector to one PAGE, as
* a one page request is never in violation.
/* 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 &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>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);
}
p->head_position = 0;
rdev->raid_disk = mirror;
@ -2255,12 +2259,14 @@ static int run(mddev_t *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_sector to one PAGE, as
* a one page request is never in violation.
* violating it, so limit max_segments to 1 lying
* within a single page.
*/
if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
blk_queue_max_hw_sectors(mddev->queue, PAGE_SIZE>>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);
}
disk->head_position = 0;
}