From 627a2d3c29427637f4c5d31ccc7fcbd8d312cd71 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 8 Mar 2010 16:44:38 +1100 Subject: 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 Cc: stable@kernel.org --- drivers/md/linear.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'drivers/md/linear.c') diff --git a/drivers/md/linear.c b/drivers/md/linear.c index af2d39d603c7..bb2a23159b21 100644 --- a/drivers/md/linear.c +++ b/drivers/md/linear.c @@ -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++; -- cgit v1.2.3