On Tue, Jan 03, 2023 at 06:31:31PM +0100, Fabio M. De Francesco wrote:
> kmap_atomic() is deprecated in favor of kmap_local_page(). Therefore,
> replace kmap_atomic() with kmap_local_page() in ips_is_passthru(). In
> the meantime remove an unnecessary comment soon before local mapping,
> align code and remove spaces (the function is short, therefore the
> reviewers job won't be over-complicated by these logically unrelated
> clean-ups).
>
> kmap_atomic() is implemented like a kmap_local_page() which also disables
> page-faults and preemption (the latter only for !PREEMPT_RT kernels).
> The code within the mapping/unmapping in ips_is_passthru() is already
> in atomic context because of a call to local_irq_save() and
> kmap_local_page() can be called in atomic context too (including
> interrupts).
>
> Therefore, a mere replacement of the old API with the new one is all it
> is required (i.e., there is no need to explicitly add any calls to
> pagefault_disable() and/or preempt_disable()).
>
> Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx>
The discussion about preemption is irrelevant AFAICS. But what you say above
is not wrong and the code looks right.
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> ---
> drivers/scsi/ips.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/scsi/ips.c b/drivers/scsi/ips.c
> index 16419aeec02d..bb206509265e 100644
> --- a/drivers/scsi/ips.c
> +++ b/drivers/scsi/ips.c
> @@ -1499,17 +1499,16 @@ static int ips_is_passthru(struct scsi_cmnd *SC)
> struct scatterlist *sg = scsi_sglist(SC);
> char *buffer;
>
> - /* kmap_atomic() ensures addressability of the user buffer.*/
> /* local_irq_save() protects the KM_IRQ0 address slot. */
> local_irq_save(flags);
> - buffer = kmap_atomic(sg_page(sg)) + sg->offset;
> - if (buffer && buffer[0] == 'C' && buffer[1] == 'O' &&
> - buffer[2] == 'P' && buffer[3] == 'P') {
> - kunmap_atomic(buffer - sg->offset);
> + buffer = kmap_local_page(sg_page(sg)) + sg->offset;
> + if (buffer && buffer[0] == 'C' && buffer[1] == 'O' &&
> + buffer[2] == 'P' && buffer[3] == 'P') {
> + kunmap_local(buffer);
> local_irq_restore(flags);
> return 1;
> }
> - kunmap_atomic(buffer - sg->offset);
> + kunmap_local(buffer);
> local_irq_restore(flags);
> }
> return 0;
> --
> 2.39.0
>
