Re: [PATCH v2 1/1] multipathd: don't leave maps read-only after write protect is cleared

[Benjamin Marzinski <bmarzins@redhat.com>]

On Wed, Oct 21, 2026 at 11:27:59AM -0700, Brian Bunker wrote:
> ev_add_path() sets mpp->force_readonly when a newly added path is
> read-only, but never clears it. If a map is created or reloaded while
> its storage is write protected, the flag stays set. When write protect
> is cleared, the reload that uev_update_path() does for the DISK_RO=0
> uevent uses the stale flag and loads the map read-only, even though all
> of its paths are read-write. uev_update_path() clears the flag after
> that reload, so the map only recovers if another DISK_RO=0 uevent
> reloads it again. If none comes, the map stays read-only, and since
> mpp->dmi.read_only is then 1, needs_ro_update() also ignores later
> DISK_RO=1 uevents for it.
> 
> Fix this by setting force_readonly before each load and clearing it
> when a load succeeds:
> 
> - needs_ro_update() now sets force_readonly whenever it returns true:
>   to 1 for a DISK_RO=1 uevent, to 0 when all of the map's paths are
>   writable, and from the paths' state when the map has no dm info.
>   uev_update_path() no longer sets or clears it itself.
> 
> - ev_add_path() sets it from all of the map's paths rather than only
>   the path being added, and only when it is about to load the map
>   (need_do_map). mpp->paths is up to date there after adopt_paths(),
>   while mpp->pg doesn't contain the new paths yet.

Oops. Good catch.

> 
> - update_map(), which does reloads that were delayed while the map was
>   waiting for udev (UDEV_WAIT_RELOAD), recomputes it from the map's
>   paths before setting up the map.
> 
> - dm_addmap() clears it after a successful load, as it does for
>   need_reload, so it can't outlive the load it was set for.
> 
> Signed-off-by: Brian Bunker <brian@purestorage.com>

Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>