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authorNeilBrown <neilb@suse.de>2010-03-08 16:44:38 +1100
committerNeilBrown <neilb@suse.de>2010-03-16 17:04:24 +1100
commit627a2d3c29427637f4c5d31ccc7fcbd8d312cd71 (patch)
treef0de68842ca3b47d0152254e60d31cc561009119 /drivers/md/raid1.c
parent25cf84cf377c0aae5dbcf937ea89bc7893db5176 (diff)
downloadlwn-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.c28
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;