On Wed, 18 Feb 2009 21:59:49 +0100
Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx> wrote:
> On Tuesday 17 February 2009, FUJITA Tomonori wrote:
> > Looks like that libata misuses dma_unmap_sg though I'm not familiar
> > with libata so I might completely misunderstand something.
> >
> > =
> > From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
> > Subject: [PATCH] fix dma_unmap_sg misuse
> >
> > DMA-mapping.txt says:
> >
> > To unmap a scatterlist, just call:
> >
> > pci_unmap_sg(pdev, sglist, nents, direction);
> >
> > Again, make sure DMA activity has already finished.
> >
> > PLEASE NOTE: The 'nents' argument to the pci_unmap_sg call must be
> > the _same_ one you passed into the pci_map_sg call,
> > it should _NOT_ be the 'count' value _returned_ from the
> > pci_map_sg call.
>
> This is correct and other subsystems (SCSI, IDE) are compliant with it.
>
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
>
> Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
Thanks,
I guess that the ide stack has the same problem (I guess that you
already knew that though).
Looks like that the ide stack in linux-next has more serious problem
about handling dma_map_sg?
In linux-next, the ide doesn't save the returned value of dma_map_sg
and assumes that dma_map_sg returns the same value to the 'nents'
argument of dma_map_sg?
Again I'm not familiar with the ide stack at all so I might completely
misunderstand something.
=
From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Date: Thu, 19 Feb 2009 21:51:17 +0900
Subject: [PATCH] ide: save the returned value of dma_map_sg
dma_map_sg could return a value different to 'nents' argument of
dma_map_sg so the ide stack needs to save it for the later usage
(e.g. for_each_sg).
The ide stack also needs to save the original sg_nents value for
pci_unmap_sg.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
---
drivers/ide/ide-dma.c | 6 +++++-
include/linux/ide.h | 1 +
2 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/drivers/ide/ide-dma.c b/drivers/ide/ide-dma.c
index b4fa861..3dbf80c 100644
--- a/drivers/ide/ide-dma.c
+++ b/drivers/ide/ide-dma.c
@@ -143,6 +143,10 @@ int ide_build_sglist(ide_drive_t *drive, struct ide_cmd *cmd)
i = dma_map_sg(hwif->dev, sg, cmd->sg_nents, cmd->sg_dma_direction);
if (i == 0)
ide_map_sg(drive, cmd);
+ else {
+ cmd->orig_sg_nents = cmd->sg_nents;
+ cmd->sg_nents = i;
+ }
return i;
}
@@ -163,7 +167,7 @@ void ide_destroy_dmatable(ide_drive_t *drive)
ide_hwif_t *hwif = drive->hwif;
struct ide_cmd *cmd = &hwif->cmd;
- dma_unmap_sg(hwif->dev, hwif->sg_table, cmd->sg_nents,
+ dma_unmap_sg(hwif->dev, hwif->sg_table, cmd->orig_sg_nents,
cmd->sg_dma_direction);
}
EXPORT_SYMBOL_GPL(ide_destroy_dmatable);
diff --git a/include/linux/ide.h b/include/linux/ide.h
index c75631c..d3465d1 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -347,6 +347,7 @@ struct ide_cmd {
int protocol;
int sg_nents; /* number of sg entries */
+ int orig_sg_nents;
int sg_dma_direction; /* DMA transfer direction */
unsigned int nbytes;
--
1.6.0.6
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