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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/multipath.c
parent25cf84cf377c0aae5dbcf937ea89bc7893db5176 (diff)
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/multipath.c')
-rw-r--r--drivers/md/multipath.c20
1 files changed, 12 insertions, 8 deletions
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 4b323f45ad7..5558ebc705c 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -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++;