[dm-devel] [PATCH v2 3/3] multipathd: avoid unnecessary path read-only reloads

[Martin Wilck]

On Wed, 2021-12-15 at 11:44 -0600, Benjamin Marzinski wrote:
> A mulitpath device can only be reloaded read/write when all paths are
> read/write. Also, whenever a read-only scsi device is rescanned, the
> scsi subsystem will first unconditionally issue a uevent with
> DISK_RO=0
> before checking the read-only status, and if it the device is still
> read-only, issuing another uevent with DISK_RO=1. These uevents cause
> pointless reloads when read-only paths are rescanned. To avoid this,
> first check if the path is being changed to the existing multipath
> read-only state. If the state is the same, do nothing. If it's
> different, check to see if all paths are read/write before changing a
> multipath device from read-only to read/write. If the multipath
> device
> read-only state is unknown, assume that it needs to be reloaded.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
Reviewed-by: Martin Wilck <mwilck at suse.com>