We tried the sd_revalidate_disk() change, just to be sure. It didn't fix it. -Ewan On Wed, May 22, 2024 at 12:49 PM Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > > On Wed, May 22, 2024 at 04:24:58PM +0200, Christoph Hellwig wrote: > > On Tue, May 21, 2024 at 10:51:17PM -0400, Mike Snitzer wrote: > > > Otherwise, blk_validate_limits() will throw-away the max_sectors that > > > was stacked from underlying device(s). In doing so it can set a > > > max_sectors limit that violates underlying device limits. > > > > Hmm, yes it sort of is "throwing the limit away", but it really > > recalculates it from max_hw_sectors, max_dev_sectors and user_max_sectors. > > Yes, but it needs to do that recalculation at each level of a stacked > device. And then we need to combine them via blk_stack_limits() -- as > is done with the various limits stacking loops in > drivers/md/dm-table.c:dm_calculate_queue_limits > > > > This caused dm-multipath IO failures like the following because the > > > underlying devices' max_sectors were stacked up to be 1024, yet > > > blk_validate_limits() defaulted max_sectors to BLK_DEF_MAX_SECTORS_CAP > > > (2560): > > > > I suspect the problem is that SCSI messed directly with max_sectors instead > > and ignores max_user_sectors (and really shouldn't touch either, but that's > > a separate discussion). Can you try the patch below and maybe also provide > > the sysfs output for max_sectors_kb and max_hw_sectors_kb for all involved > > devices? > > FYI, you can easily reproduce with: > > git clone https://github.com/snitm/mptest.git > cd mptest > <edit so it uses: export MULTIPATH_BACKEND_MODULE="scsidebug"> > ./runtest ./tests/test_00_no_failure > > Also, best to change this line: > ./lib/mpath_generic: local _feature="4 queue_if_no_path retain_attached_hw_handler queue_mode $MULTIPATH_QUEUE_MODE" > to: > ./lib/mpath_generic: local _feature="3 retain_attached_hw_handler queue_mode $MULTIPATH_QUEUE_MODE" > Otherwise the test will hang due to queue_if_no_path. > > all underlying scsi-debug scsi devices: > > ./max_hw_sectors_kb:2147483647 > ./max_sectors_kb:512 > > multipath device: > > before my fix: > ./max_hw_sectors_kb:2147483647 > ./max_sectors_kb:1280 > > after my fix: > ./max_hw_sectors_kb:2147483647 > ./max_sectors_kb:512 > > > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c > > index 332eb9dac22d91..f6c822c9cbd2d3 100644 > > --- a/drivers/scsi/sd.c > > +++ b/drivers/scsi/sd.c > > @@ -3700,8 +3700,10 @@ static int sd_revalidate_disk(struct gendisk *disk) > > */ > > if (sdkp->first_scan || > > q->limits.max_sectors > q->limits.max_dev_sectors || > > - q->limits.max_sectors > q->limits.max_hw_sectors) > > + q->limits.max_sectors > q->limits.max_hw_sectors) { > > q->limits.max_sectors = rw_max; > > + q->limits.max_user_sectors = rw_max; > > + } > > > > sdkp->first_scan = 0; > > > > > > Driver shouldn't be changing max_user_sectors.. > > But it also didn't fix it (mpath still gets ./max_sectors_kb:1280): > > [ 74.872485] blk_insert_cloned_request: over max size limit. (2048 > 1024) > [ 74.872505] device-mapper: multipath: 254:3: Failing path 8:16. > [ 74.872620] blk_insert_cloned_request: over max size limit. (2048 > 1024) > [ 74.872641] device-mapper: multipath: 254:3: Failing path 8:32. > [ 74.872712] blk_insert_cloned_request: over max size limit. (2048 > 1024) > [ 74.872732] device-mapper: multipath: 254:3: Failing path 8:48. > [ 74.872788] blk_insert_cloned_request: over max size limit. (2048 > 1024) > [ 74.872808] device-mapper: multipath: 254:3: Failing path 8:64. > > Simply setting max_user_sectors won't help with stacked devices > because blk_stack_limits() doesn't stack max_user_sectors. It'll > inform the underlying device's blk_validate_limits() calculation which > will result in max_sectors having the desired value (which it already > did, as I showed above). But when stacking limits from underlying > devices up to the higher-level dm-mpath queue_limits we still have > information loss. > > Mike >
