path: root/block/blk-settings.c
diff options
authorMilan Broz <>2008-12-03 12:55:08 +0100
committerJens Axboe <>2008-12-03 12:55:55 +0100
commit0e435ac26e3f951d83338ed3d4ab7dc0fe0055bc (patch)
tree8f208a3093de1a314a981ae47e5ef92a5909c13b /block/blk-settings.c
parent53a08807c01989c6847bb135d8d43f61c5dfdda5 (diff)
block: fix setting of max_segment_size and seg_boundary mask
Fix setting of max_segment_size and seg_boundary mask for stacked md/dm devices. When stacking devices (LVM over MD over SCSI) some of the request queue parameters are not set up correctly in some cases by default, namely max_segment_size and and seg_boundary mask. If you create MD device over SCSI, these attributes are zeroed. Problem become when there is over this mapping next device-mapper mapping - queue attributes are set in DM this way: request_queue max_segment_size seg_boundary_mask SCSI 65536 0xffffffff MD RAID1 0 0 LVM 65536 -1 (64bit) Unfortunately bio_add_page (resp. bio_phys_segments) calculates number of physical segments according to these parameters. During the generic_make_request() is segment cout recalculated and can increase bio->bi_phys_segments count over the allowed limit. (After bio_clone() in stack operation.) Thi is specially problem in CCISS driver, where it produce OOPS here BUG_ON(creq->nr_phys_segments > MAXSGENTRIES); (MAXSEGENTRIES is 31 by default.) Sometimes even this command is enough to cause oops: dd iflag=direct if=/dev/<vg>/<lv> of=/dev/null bs=128000 count=10 This command generates bios with 250 sectors, allocated in 32 4k-pages (last page uses only 1024 bytes). For LVM layer, it allocates bio with 31 segments (still OK for CCISS), unfortunatelly on lower layer it is recalculated to 32 segments and this violates CCISS restriction and triggers BUG_ON(). The patch tries to fix it by: * initializing attributes above in queue request constructor blk_queue_make_request() * make sure that blk_queue_stack_limits() inherits setting (DM uses its own function to set the limits because it blk_queue_stack_limits() was introduced later. It should probably switch to use generic stack limit function too.) * sets the default seg_boundary value in one place (blkdev.h) * use this mask as default in DM (instead of -1, which differs in 64bit) Bugs related to this: Signed-off-by: Milan Broz <> Reviewed-by: Alasdair G Kergon <> Cc: Neil Brown <> Cc: FUJITA Tomonori <> Cc: Tejun Heo <> Cc: Mike Miller <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/blk-settings.c')
1 files changed, 4 insertions, 0 deletions
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 41392fbe19ff..afa55e14e278 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -125,6 +125,9 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
q->nr_requests = BLKDEV_MAX_RQ;
blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
+ blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);
+ blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
q->make_request_fn = mfn;
q->backing_dev_info.ra_pages =
@@ -314,6 +317,7 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
/* zero is "infinity" */
t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
+ t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask, b->seg_boundary_mask);
t->max_phys_segments = min(t->max_phys_segments, b->max_phys_segments);
t->max_hw_segments = min(t->max_hw_segments, b->max_hw_segments);