From: Lars Ellenberg <lars.ellenberg@linbit.com>
X-Patchwork-Id: 83666
FIXME Missing header & signoff
FIXME Needs recent test evidence of failure without the patch
Speaking of...
dm_set_device_limits is still doing things wrong here, I think.
I posted this about two years ago, but somehow it got lost
and I lost it from my focus as well.
Reading this post reminded me ... there was something:
---
drivers/md/dm-table.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
Index: linux/drivers/md/dm-table.c
===================================================================
--- linux.orig/drivers/md/dm-table.c
+++ linux/drivers/md/dm-table.c
@@ -518,9 +518,21 @@ int dm_set_device_limits(struct dm_targe
* smaller I/O, just to be safe.
*/
- if (q->merge_bvec_fn && !ti->type->merge)
+ if (q->merge_bvec_fn && !ti->type->merge) {
blk_limits_max_hw_sectors(limits,
(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 trigger this.
+ */
+ limits->max_segments = 1;
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(dm_set_device_limits);