From: SeongJae Park <sjpark@xxxxxxxxx> Persistent grants feature provides high scalability. On some small systems, however, it could incur data copy overheads[1] and thus it is required to be disabled. But, there is no option to disable it. For the reason, this commit adds module parameters for disabling of the feature. [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability Baseline and Complete Git Trees =============================== The patches are based on the v5.9-rc6. You can also clone the complete git tree: $ git clone git://github.com/sjp38/linux -b pgrants_disable_v4 The web is also available: https://github.com/sjp38/linux/tree/pgrants_disable_v4 Patch History ============= Changes from v3 (https://lore.kernel.org/xen-devel/20200922141549.26154-2-sjpark@xxxxxxxxxx/) - Remove unnecessary ternary operation (Jürgen Groß) - Add 'Reviewed-by: Juergen Gross <jgross@xxxxxxxx>' and 'Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>' Changes from v2 (https://lore.kernel.org/linux-block/20200922105209.5284-1-sjpark@xxxxxxxxxx/) - Avoid a race condition (Roger Pau Monné) Because the option value is written twice, there could be a race if the user change the value meanwhile. This version fixes the problem by reading the value once when each (front|back)end is created. Changes from v1 (https://lore.kernel.org/linux-block/20200922070125.27251-1-sjpark@xxxxxxxxxx/) - use 'bool' parameter type (Jürgen Groß) - Let blkfront can also disable the feature from its side (Roger Pau Monné) - Avoid unnecessary xenbus_printf (Roger Pau Monné) - Update frontend parameter doc SeongJae Park (3): xen-blkback: add a parameter for disabling of persistent grants xen-blkfront: add a parameter for disabling of persistent grants xen-blkfront: Apply changed parameter name to the document .../ABI/testing/sysfs-driver-xen-blkback | 9 ++++++++ .../ABI/testing/sysfs-driver-xen-blkfront | 11 +++++++++- drivers/block/xen-blkback/xenbus.c | 22 ++++++++++++++----- drivers/block/xen-blkfront.c | 20 ++++++++++++----- 4 files changed, 50 insertions(+), 12 deletions(-) -- 2.17.1
