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authorMike Snitzer <snitzer@redhat.com>2012-09-26 22:45:45 (GMT)
committerAlasdair G Kergon <agk@redhat.com>2012-09-26 22:45:45 (GMT)
commit3ae706561637331aa578e52bb89ecbba5edcb7a9 (patch)
tree681ff02fc4687617e9293ac3c28919ec26f225b0 /net
parentc3c4555edd10dbc0b388a0125b9c50de5e79af05 (diff)
downloadlinux-3ae706561637331aa578e52bb89ecbba5edcb7a9.tar.xz
dm: retain table limits when swapping to new table with no devices
Add a safety net that will re-use the DM device's existing limits in the event that DM device has a temporary table that doesn't have any component devices. This is to reduce the chance that requests not respecting the hardware limits will reach the device. DM recalculates queue limits based only on devices which currently exist in the table. This creates a problem in the event all devices are temporarily removed such as all paths being lost in multipath. DM will reset the limits to the maximum permissible, which can then assemble requests which exceed the limits of the paths when the paths are restored. The request will fail the blk_rq_check_limits() test when sent to a path with lower limits, and will be retried without end by multipath. This became a much bigger issue after v3.6 commit fe86cdcef ("block: do not artificially constrain max_sectors for stacking drivers"). Reported-by: David Jeffery <djeffery@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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