From: SeongJae Park sj@kernel.org
commit 402c43ea6b34a1b371ffeed9adf907402569eaf5 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.
Similar behavioral change has made on 'blkfront' by commit 74a852479c68 ("xen-blkfront: add a parameter for disabling of persistent grants"). This commit changes the behavior of the parameter to make effect for every connect, so that the previous behavior of 'blkfront' can be restored.
[1] https://lore.kernel.org/xen-devel/CAJwUmVB6H3iTs-C+U=v-pwJB7-_ZRHPxHzKRJZ22x...
Fixes: 74a852479c68 ("xen-blkfront: add a parameter for disabling of persistent grants") Cc: stable@vger.kernel.org # 5.10.x 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/20220715225108.193398-4-sj@kernel.org Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Documentation/ABI/testing/sysfs-driver-xen-blkfront | 2 +- drivers/block/xen-blkfront.c | 4 +--- 2 files changed, 2 insertions(+), 4 deletions(-)
--- a/Documentation/ABI/testing/sysfs-driver-xen-blkfront +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkfront @@ -15,5 +15,5 @@ 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 frontends. + that this option only takes effect on newly connected frontends. The default is Y (enable). --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2088,8 +2088,6 @@ static int blkfront_probe(struct xenbus_ info->vdevice = vdevice; info->connected = BLKIF_STATE_DISCONNECTED;
- info->feature_persistent = feature_persistent; - /* Front end dir is a number, which is used as the id. */ info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0); dev_set_drvdata(&dev->dev, info); @@ -2393,7 +2391,7 @@ static void blkfront_gather_backend_feat if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0)) blkfront_setup_discard(info);
- if (info->feature_persistent) + if (feature_persistent) info->feature_persistent = !!xenbus_read_unsigned(info->xbdev->otherend, "feature-persistent", 0);