null_blk: remove hardcoded alloc_cmd() parameter
Only caller of alloc_cmd() is null_submit_bio() unconditionally sets second parameter to true and that is statically hard-coded in null_blk. There is no point in having statically hardcoded function parameter. Remove the unnecessary parameter can_wait and adjust the code so it can retain existing behavior of waiting when we don't get valid nullb_cmd from __alloc_cmd() in alloc_cmd(). The restructured code avoids multiple return statements, multiple calls to __alloc_cmd() and resulting a fast path call to prepare_to_wait() due to removal of first alloc_cmd() call. Follow the pattern that we have in bio_alloc() to set the structure members in the structure allocation function in alloc_cmd() and pass bio to initialize newly allocated cmd->bio member. Follow the pattern in copy_to_nullb() to use result of one function call (null_cache_active()) to be used as a parameter to another function call (null_insert_page()), use result of alloc_cmd() as a first parameter to the null_handle_cmd() in null_submit_bio() function. This allow us to remove the local variable cmd on stack in null_submit_bio() that is in fast path. Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com> Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Link: https://lore.kernel.org/r/20220216172945.31124-2-kch@nvidia.comSigned-off-by: Jens Axboe <axboe@kernel.dk>
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