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xen-blkfront: Apply 'feature_persistent' parameter when connect 

commit 402c43ea6b 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 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
SeongJae Park 2022-07-15 22:51:08 +00:00 committed by Greg Kroah-Hartman
parent 0081c64ab8
commit 31dc3b1562
2 changed files with 2 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/ABI/testing/sysfs-driver-xen-blkfront
View File

@ -15,5 +15,5 @@ KernelVersion: 5.10
Contact: SeongJae Park <sj@kernel.org>
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).

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

@ -2011,8 +2011,6 @@ static int blkfront_probe(struct xenbus_device *dev,
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);
@ -2306,7 +2304,7 @@ static void blkfront_gather_backend_features(struct blkfront_info *info)
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);