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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>
20 lines
942 B
Plaintext
20 lines
942 B
Plaintext
What: /sys/module/xen_blkfront/parameters/max_indirect_segments
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Date: June 2013
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KernelVersion: 3.11
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Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Description:
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Maximum number of segments that the frontend will negotiate
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with the backend for indirect descriptors. The default value
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is 32 - higher value means more potential throughput but more
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memory usage. The backend picks the minimum of the frontend
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and its default backend value.
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What: /sys/module/xen_blkfront/parameters/feature_persistent
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Date: September 2020
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KernelVersion: 5.10
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Contact: Maximilian Heyne <mheyne@amazon.de>
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Description:
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Whether to enable the persistent grants feature or not. Note
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that this option only takes effect on newly connected frontends.
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The default is Y (enable).
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