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| author | NeilBrown <neilb@suse.de> | 2010-03-08 16:44:38 +1100 |
|---|---|---|
| committer | NeilBrown <neilb@suse.de> | 2010-03-16 17:04:24 +1100 |
| commit | 627a2d3c29427637f4c5d31ccc7fcbd8d312cd71 (patch) | |
| tree | f0de68842ca3b47d0152254e60d31cc561009119 /drivers/md/raid1.c | |
| parent | 25cf84cf377c0aae5dbcf937ea89bc7893db5176 (diff) | |
| download | lwn-627a2d3c29427637f4c5d31ccc7fcbd8d312cd71.tar.gz lwn-627a2d3c29427637f4c5d31ccc7fcbd8d312cd71.zip | |
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
Diffstat (limited to 'drivers/md/raid1.c')
| -rw-r--r-- | drivers/md/raid1.c | 28 |
1 files changed, 17 insertions, 11 deletions
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 5a06122abd3b..f741f77eeb2b 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -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; |