• Fabio M. De Francesco's avatar
    scsi: ipr: Replace kmap() with kmap_local_page() · a3e2e248
    Fabio M. De Francesco authored
    The use of kmap() is deprecated in favor of kmap_local_page().
    
    There are two main problems with kmap(): (1) It comes with an overhead as
    the mapping space is restricted and protected by a global lock for
    synchronization and (2) it also requires global TLB invalidation when the
    kmap’s pool wraps and it might block when the mapping space is fully
    utilized until a slot becomes available.
    
    With kmap_local_page() the mappings are per thread, CPU local, can take
    page faults, and can be called from any context (including interrupts).  It
    is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the
    tasks can be preempted and, when they are scheduled to run again, the
    kernel virtual addresses are restored and still valid.
    
    Therefore, replace kmap() with kmap_local_page() in ipr_copy_ucode_buffer()
    and, instead of open-coding local mappings + memcpy() + local un-mappings,
    use the better suited memcpy_to_page() helper.
    Suggested-by: default avatarIra Weiny <ira.weiny@intel.com>
    Signed-off-by: default avatarFabio M. De Francesco <fmdefrancesco@gmail.com>
    Link: https://lore.kernel.org/r/20230103182556.29080-1-fmdefrancesco@gmail.comSigned-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
    a3e2e248
ipr.c 302 KB