dm_set_device_limits: when ignoring q->merge_bvec_fn, set rs->max_phys_segments to one to avoid violating it
PATCH 1/1 dm_set_device_limits: when ignoring q->merge_bvec_fn, set rs->max_phys_segments to one to avoid violating it
Restricting max_sectors is not enough.
If someone uses bio_add_page to add 8 disjunct 512 byte partial pages to a bio, it would succeed,
but could still cross a border of whatever restrictions are below us (raid0 stripe boundary). An attempted bio_split would not succeed, because bi_vcnt is 8. E.g. the xen io layer is known to do trigger this.
Signed-off-by Lars Ellenberg <[email protected]>
---
should maybe be "backported" to the stable series kernels as well, at least if one plans to use xen vm's on top of lvm on top of md or drbd.
drivers/md/dm-table.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-)
drivers/md/dm-table.c +12 -1
@@ -512,11 +512,22 @@ void dm_set_device_limits(struct dm_target *ti, struct block_device *bdev)* smaller I/O, just to be safe. */ -if (q->merge_bvec_fn && !ti->type->merge) +if (q->merge_bvec_fn && !ti->type->merge) { rs->max_sectors =min_not_zero (rs->max_sectors, (unsigned int ) (PAGE_SIZE >>9 )); +/* Restricting max_sectors is not enough. +* If someone uses bio_add_page to add 8 disjunct 512 byte +* partial pages to a bio, it would succeed, +* but could still cross a border of whatever restrictions +* are below us (raid0 stripe boundary). An attempted +* bio_split would not succeed, because bi_vcnt is 8. +* E.g. the xen io layer is known to do trigger this. +*/ + rs->max_phys_segments =1 ; + } + rs->max_phys_segments =min_not_zero (rs->max_phys_segments, q->max_phys_segments);
Signature · 6 lines
1.5.5.GIT -- : Lars Ellenberg Tel +43-1-8178292-55 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Vivenotgasse 48, A-1120 Vienna/Europe http://www.linbit.com :