Hi
I hope this address is the right place for this patch.
It is supposed to fix the triggering of block/blklib.c:51 WARN_ON_ONCE(..) when using LVM2 raid1 with SSD-PVs.
Since commit b35fd7422c2f8e04496f5a770bd4e1a205414b3f and without this patchthere are tons of printks logging "Error: discard_granularity is 0." to kmsg.
Also there is no discard/TRIM happening anymore...
This is a rough patch for WARNING-issue
"block/blk-lib.c:51 __blkdev_issue_discard+0x1f6/0x250"
[...] "Error: discard_granularity is 0." [...]
introduced in commit b35fd7422c2f8e04496f5a770bd4e1a205414b3f
("block: check queue's limits.discard_granularity in __blkdev_issue_discard()")
in conjunction with LVM2 raid1 volumes on discardable (SSD) backing.
It seems until now, LVM-raid1 reported "discard_granularity" as 0,
as well as "max_discard_sectors" as 0. (see "lsblk --discard").
The idea here is to fix the issue by calculating "max_discard_sectors"
as the minimum over all involved block devices. (We use the meta-data
for this to work here.)
For calculating the "discard_granularity" we would have to calculate the
lcm (least common multiple) of all discard_granularities of all involved
block devices and finally round up to next power of 2.
However, since all "discard_granularity" are powers of 2, this algorithm
will simplify to just determining the maximum and filtering for "0"-cases.
Signed-off-by: Stephan Baerwolf <stephan@xxxxxxxxxxxxxxx>
---
drivers/md/dm-raid.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 8d2b835d7a10..4c769fd93ced 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3734,8 +3734,36 @@ static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
* RAID0/4/5/6 don't and process large discard bios properly.
*/
if (rs_is_raid1(rs) || rs_is_raid10(rs)) {
- limits->discard_granularity = chunk_size_bytes;
- limits->max_discard_sectors = rs->md.chunk_sectors;
+ /* HACK */
+ if (chunk_size_bytes==0) {
+ unsigned int i, chunk_sectors=(UINT_MAX >> SECTOR_SHIFT);
+ struct request_queue *q = NULL;
+
+ DMINFO("chunk_size is 0 for raid1 - preventing issue with TRIM");
+
+ for (i=0;i<rs->raid_disks;i++) {
+ q=bdev_get_queue(rs->dev[i].meta_dev->bdev);
+ if (chunk_sectors > q->limits.max_discard_sectors) {
+ chunk_sectors = q->limits.max_discard_sectors;
+ }
+ if (chunk_size_bytes < q->limits.discard_granularity) {
+ chunk_size_bytes = q->limits.discard_granularity;
+ }
+
+ /* lcm(x,y,...,0) = 0 */
+ if (q->limits.discard_granularity == 0) {
+ chunk_size_bytes = 0;
+ break;
+ }
+ }
+
+ limits->discard_granularity = chunk_size_bytes;
+ limits->max_discard_sectors = chunk_sectors;
+ /* end of HACK (but not of if) */
+ } else {
+ limits->discard_granularity = chunk_size_bytes;
+ limits->max_discard_sectors = rs->md.chunk_sectors;
+ }
}
}
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