Commit e94c6101 authored by Maximilian Heyne's avatar Maximilian Heyne Committed by Juergen Gross

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 aac8a70d ("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: default avatarAndrii Chepurnyi <andrii.chepurnyi82@gmail.com>
Fixes: aac8a70d ("xen-blkback: add a parameter for disabling of persistent grants")
Cc: <stable@vger.kernel.org> # 5.10.x
Signed-off-by: default avatarMaximilian Heyne <mheyne@amazon.de>
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Reviewed-by: default avatarMaximilian Heyne <mheyne@amazon.de>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220715225108.193398-3-sj@kernel.orgSigned-off-by: default avatarJuergen Gross <jgross@suse.com>
parent fc9be616
...@@ -42,5 +42,5 @@ KernelVersion: 5.10 ...@@ -42,5 +42,5 @@ KernelVersion: 5.10
Contact: Maximilian Heyne <mheyne@amazon.de> Contact: Maximilian Heyne <mheyne@amazon.de>
Description: Description:
Whether to enable the persistent grants feature or not. Note 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). The default is Y (enable).
...@@ -186,8 +186,6 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) ...@@ -186,8 +186,6 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
__module_get(THIS_MODULE); __module_get(THIS_MODULE);
INIT_WORK(&blkif->free_work, xen_blkif_deferred_free); INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
blkif->vbd.feature_gnt_persistent = feature_persistent;
return blkif; return blkif;
} }
...@@ -1086,10 +1084,9 @@ static int connect_ring(struct backend_info *be) ...@@ -1086,10 +1084,9 @@ static int connect_ring(struct backend_info *be)
xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol); xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
return -ENOSYS; return -ENOSYS;
} }
if (blkif->vbd.feature_gnt_persistent)
blkif->vbd.feature_gnt_persistent = blkif->vbd.feature_gnt_persistent = feature_persistent &&
xenbus_read_unsigned(dev->otherend, xenbus_read_unsigned(dev->otherend, "feature-persistent", 0);
"feature-persistent", 0);
blkif->vbd.overflow_max_grants = 0; blkif->vbd.overflow_max_grants = 0;
......
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