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xen-blkfront: Apply 'feature_persistent' parameter when connect

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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 aac8a70db2 ("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 74a852479c
("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-_ZRHPxHzKRJZ22xEPW7z8a=g@mail.gmail.com/

Fixes: 74a852479c ("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>
This commit is contained in:
SeongJae Park 2022-07-15 22:51:08 +00:00 committed by Juergen Gross
parent e94c6101e1
commit 402c43ea6b
2 changed files with 2 additions and 4 deletions
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2
Documentation/ABI/testing/sysfs-driver-xen-blkfront
View File

@ -15,5 +15,5 @@ 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 frontends. that this option only takes effect on newly connected frontends.
The default is Y (enable). The default is Y (enable).

4
drivers/block/xen-blkfront.c
View File

@ -1988,8 +1988,6 @@ static int blkfront_probe(struct xenbus_device *dev,
info->vdevice = vdevice; info->vdevice = vdevice;
info->connected = BLKIF_STATE_DISCONNECTED; info->connected = BLKIF_STATE_DISCONNECTED;
info->feature_persistent = feature_persistent;
/* Front end dir is a number, which is used as the id. */ /* Front end dir is a number, which is used as the id. */
info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0); info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
dev_set_drvdata(&dev->dev, info); dev_set_drvdata(&dev->dev, info);
@ -2283,7 +2281,7 @@ static void blkfront_gather_backend_features(struct blkfront_info *info)
if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0)) if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0))
blkfront_setup_discard(info); blkfront_setup_discard(info);
if (info->feature_persistent) if (feature_persistent)
info->feature_persistent = info->feature_persistent =
!!xenbus_read_unsigned(info->xbdev->otherend, !!xenbus_read_unsigned(info->xbdev->otherend,
"feature-persistent", 0); "feature-persistent", 0);