On Tue, May 13, 2025 at 01:37:30PM +0200, Kevin Wolf wrote: > When scsi-block is used on a host multipath device, it runs into the > problem that the kernel dm-mpath doesn't know anything about SCSI or > SG_IO and therefore can't decide if a SG_IO request returned an error > and needs to be retried on a different path. Instead of getting working > failover, an error is returned to scsi-block and handled according to > the configured error policy. Obviously, this is not what users want, > they want working failover. > > QEMU can parse the SG_IO result and determine whether this could have > been a path error, but just retrying the same request could just send it > to the same failing path again and result in the same error. > > With a kernel that supports the DM_MPATH_PROBE_PATHS ioctl on dm-mpath > block devices (queued in the device mapper tree for Linux 6.16), we can > tell the kernel to probe all paths and tell us if any usable paths > remained. If so, we can now retry the SG_IO ioctl and expect it to be > sent to a working path. > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > --- > block/file-posix.c | 82 +++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 81 insertions(+), 1 deletion(-)
Maybe the probability of retry success would be higher with a delay so that intermittent issues have time to resolve themselves. Either way, the patch looks good. Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
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