* Re: [PATCH] ide-scsi highmem cleanup
[not found] <200510310302.j9V32hO4009277@hera.kernel.org>
@ 2005-10-31 3:48 ` Jeff Garzik
2005-10-31 4:00 ` Andrew Morton
0 siblings, 1 reply; 2+ messages in thread
From: Jeff Garzik @ 2005-10-31 3:48 UTC (permalink / raw)
To: Andrew Morton
Cc: Linux Kernel Mailing List, Linus Torvalds,
Bartlomiej Zolnierkiewicz, linux-ide, Alan Cox
Linux Kernel Mailing List wrote:
> tree c6016a8741a2527acac0ceb6e6ce431a798d6708
> parent f1fc78a8c7f3a784b9fd1e07cc1438a0ea569555
> author Andrew Morton <akpm@osdl.org> Mon, 31 Oct 2005 07:00:13 -0800
> committer Linus Torvalds <torvalds@g5.osdl.org> Mon, 31 Oct 2005 09:37:17 -0800
>
> [PATCH] ide-scsi highmem cleanup
>
> It's not necessary to test PageHighmem in here - kmap_atomic() does the right
> thing.
>
> Cc: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
>
> drivers/scsi/ide-scsi.c | 38 ++++++++++++--------------------------
> 1 files changed, 12 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/scsi/ide-scsi.c b/drivers/scsi/ide-scsi.c
> --- a/drivers/scsi/ide-scsi.c
> +++ b/drivers/scsi/ide-scsi.c
> @@ -180,19 +180,12 @@ static void idescsi_input_buffers (ide_d
> return;
> }
> count = min(pc->sg->length - pc->b_count, bcount);
> - if (PageHighMem(pc->sg->page)) {
> - unsigned long flags;
> -
> - local_irq_save(flags);
> - buf = kmap_atomic(pc->sg->page, KM_IRQ0) + pc->sg->offset;
> - drive->hwif->atapi_input_bytes(drive, buf + pc->b_count, count);
> - kunmap_atomic(buf - pc->sg->offset, KM_IRQ0);
> - local_irq_restore(flags);
> - } else {
> - buf = page_address(pc->sg->page) + pc->sg->offset;
> - drive->hwif->atapi_input_bytes(drive, buf + pc->b_count, count);
> - }
> - bcount -= count; pc->b_count += count;
> + buf = kmap_atomic(pc->sg->page, KM_IRQ0);
> + drive->hwif->atapi_input_bytes(drive,
> + buf + pc->b_count + pc->sg->offset, count);
> + kunmap_atomic(buf, KM_IRQ0);
> + bcount -= count;
> + pc->b_count += count;
> if (pc->b_count == pc->sg->length) {
> pc->sg++;
> pc->b_count = 0;
> @@ -212,19 +205,12 @@ static void idescsi_output_buffers (ide_
> return;
> }
> count = min(pc->sg->length - pc->b_count, bcount);
> - if (PageHighMem(pc->sg->page)) {
> - unsigned long flags;
> -
> - local_irq_save(flags);
> - buf = kmap_atomic(pc->sg->page, KM_IRQ0) + pc->sg->offset;
> - drive->hwif->atapi_output_bytes(drive, buf + pc->b_count, count);
> - kunmap_atomic(buf - pc->sg->offset, KM_IRQ0);
> - local_irq_restore(flags);
> - } else {
> - buf = page_address(pc->sg->page) + pc->sg->offset;
> - drive->hwif->atapi_output_bytes(drive, buf + pc->b_count, count);
> - }
> - bcount -= count; pc->b_count += count;
> + buf = kmap_atomic(pc->sg->page, KM_IRQ0);
> + drive->hwif->atapi_output_bytes(drive,
> + buf + pc->b_count + pc->sg->offset, count);
> + kunmap_atomic(buf, KM_IRQ0);
> + bcount -= count;
> + pc->b_count += count;
Unless I'm missing something, this patch looks very wrong.
kmap_atomic(..., KM_IRQx) needs to be inside local_irq_save().
As such, the PageHighMem() does have clear benefits.
Jeff
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