xen-blkback: Apply 'feature_persistent' parameter when connect
authorMaximilian Heyne <mheyne@amazon.de>
Fri, 15 Jul 2022 22:51:07 +0000 (22:51 +0000)
committerJuergen Gross <jgross@suse.com>
Fri, 12 Aug 2022 10:13:51 +0000 (12:13 +0200)
commite94c6101e151b019b8babc518ac2a6ada644a5a1
tree05b1ff3635bb1118c0611c6fc245740920af43a6
parentfc9be616bb8f3ed9cf560308f86904f5c06be205
xen-blkback: Apply 'feature_persistent' parameter when connect

In some use cases[1], the backend is created while the frontend doesn't
support the persistent grants feature, but later the frontend can be
changed to support the feature and reconnect.  In the past, 'blkback'
enabled the persistent grants feature since it unconditionally checked
if frontend supports the persistent grants feature for every connect
('connect_ring()') and decided whether it should use persistent grans or
not.

However, commit aac8a70db24b ("xen-blkback: add a parameter for
disabling of persistent grants") has mistakenly changed the behavior.
It made the frontend feature support check to not be repeated once it
shown the 'feature_persistent' as 'false', or the frontend doesn't
support persistent grants.

This commit changes the behavior of the parameter to make effect for
every connect, so that the previous workflow can work again as expected.

[1] https://lore.kernel.org/xen-devel/CAJwUmVB6H3iTs-C+U=v-pwJB7-_ZRHPxHzKRJZ22xEPW7z8a=g@mail.gmail.com/

Reported-by: Andrii Chepurnyi <andrii.chepurnyi82@gmail.com>
Fixes: aac8a70db24b ("xen-blkback: add a parameter for disabling of persistent grants")
Cc: <stable@vger.kernel.org> # 5.10.x
Signed-off-by: Maximilian Heyne <mheyne@amazon.de>
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Maximilian Heyne <mheyne@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220715225108.193398-3-sj@kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Documentation/ABI/testing/sysfs-driver-xen-blkback
drivers/block/xen-blkback/xenbus.c