From: Maximilian Heyne mheyne@amazon.de
stable inclusion from stable-v5.10.137 commit d4fb08e5a4b46666ba4ad4a9025957973ccb721a category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit e94c6101e151b019b8babc518ac2a6ada644a5a1 upstream.
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-_ZRHPxHzKRJZ22x...
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Reviewed-by: Wei Li liwei391@huawei.com --- Documentation/ABI/testing/sysfs-driver-xen-blkback | 2 +- drivers/block/xen-blkback/xenbus.c | 9 +++------ 2 files changed, 4 insertions(+), 7 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback index ac2947b98950..3d5de44cbbee 100644 --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback @@ -42,5 +42,5 @@ KernelVersion: 5.10 Contact: SeongJae Park sjpark@amazon.de Description: Whether to enable the persistent grants feature or not. Note - that this option only takes effect on newly created backends. + that this option only takes effect on newly connected backends. The default is Y (enable). diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 6f549f6c1c3e..44782b15b9fd 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -186,8 +186,6 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) __module_get(THIS_MODULE); INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
- blkif->vbd.feature_gnt_persistent = feature_persistent; - return blkif; }
@@ -1090,10 +1088,9 @@ static int connect_ring(struct backend_info *be) xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol); return -ENOSYS; } - if (blkif->vbd.feature_gnt_persistent) - blkif->vbd.feature_gnt_persistent = - xenbus_read_unsigned(dev->otherend, - "feature-persistent", 0); + + blkif->vbd.feature_gnt_persistent = feature_persistent && + xenbus_read_unsigned(dev->otherend, "feature-persistent", 0);
blkif->vbd.overflow_max_grants = 0;