ublk: lift checks out of ublk_{,un}map_io()

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ublk_map_io() and ublk_unmap_io() are no-ops for ublk devices that
enable user copy or zero copy, as well as for requests without data to
copy in the given direction. However, the implementation is a bit
convoluted, returning the full request data length and relying on the
caller to check the return value against the request length.
UBLK_F_SHMEM_ZC recently added branches to skip the ublk_{,un}map_io()
call for I/Os using a shared-memory buffer. This is a more logical place
for the device need_map and the ublk_need_{,un}map_req() checks, so move
them there from ublk_{,un}map_io().

Checking these conditions early also skips the expensive pointer-chasing
for the ublk_iod_is_shmem_zc() check in __ublk_complete_rq() for the
common case of a ublk device using user copy or zero copy.

Drop the req_op() filter in __ublk_complete_rq(), as it's redundant with
the ublk_need_unmap_req() check.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Link: https://patch.msgid.link/20260803211441.2538144-9-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Caleb Sander Mateos 2026-08-03 15:14:40 -06:00 • committed by Jens Axboe

parent d61d0f95e6

commit a8a79eba22

1 changed files with 19 additions and 51 deletions

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drivers/block/ublk_drv.c

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