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SubjectRe: [ide] b7fb14d3ac: EIP:ioread32_rep
On Wed, Jul 07, 2021 at 10:12:20AM +0200, Christoph Hellwig wrote:
> On Tue, Jul 06, 2021 at 12:08:42PM -0700, Linus Torvalds wrote:
> > On Tue, Jul 6, 2021 at 7:36 AM Christoph Hellwig <hch@lst.de> wrote:
> > >
> > > Yeah, there's usually a huge offset into the page. The otherwise
> > > similar ATAPI code actually has checks to chunk it up and not cross
> > > page boundaries, and copying that over fixes the problem.
> >
> > Ok.
> >
> > Your patch made me go "I think it should loop until it has transferred
> > the full 512 bytes", but maybe the caller loops properly?
>
> Yes, the callers (ata_read_pio_sectors) does).

Actually, not it doesn't. Sorry. So for a non-aligned large request
this won't work. So we'll need to actually loop here.

This is probably better and fixes the issue as well (and ATAPI
probably needs the same treatment):


diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index ae7189d1a568..40d2dc3b2989 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -637,6 +637,20 @@ unsigned int ata_sff_data_xfer32(struct ata_queued_cmd *qc, unsigned char *buf,
}
EXPORT_SYMBOL_GPL(ata_sff_data_xfer32);

+static void ata_pio_xfer(struct ata_queued_cmd *qc, struct page *page,
+ unsigned int offset, size_t xfer_size)
+{
+ bool do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
+ unsigned char *buf;
+
+ buf = kmap_atomic(page);
+ qc->ap->ops->sff_data_xfer(qc, buf + offset, xfer_size, do_write);
+ kunmap_atomic(buf);
+
+ if (!do_write && !PageSlab(page))
+ flush_dcache_page(page);
+}
+
/**
* ata_pio_sector - Transfer a sector of data.
* @qc: Command on going
@@ -648,11 +662,9 @@ EXPORT_SYMBOL_GPL(ata_sff_data_xfer32);
*/
static void ata_pio_sector(struct ata_queued_cmd *qc)
{
- int do_write = (qc->tf.flags & ATA_TFLAG_WRITE);
struct ata_port *ap = qc->ap;
struct page *page;
unsigned int offset;
- unsigned char *buf;

if (!qc->cursg) {
qc->curbytes = qc->nbytes;
@@ -670,13 +682,15 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)

DPRINTK("data %s\n", qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");

- /* do the actual data transfer */
- buf = kmap_atomic(page);
- ap->ops->sff_data_xfer(qc, buf + offset, qc->sect_size, do_write);
- kunmap_atomic(buf);
+ if (offset + qc->sect_size > PAGE_SIZE) {
+ unsigned int split_len = PAGE_SIZE - offset;

- if (!do_write && !PageSlab(page))
- flush_dcache_page(page);
+ ata_pio_xfer(qc, page, offset, split_len);
+ ata_pio_xfer(qc, nth_page(page, 1), 0,
+ qc->sect_size - split_len);
+ } else {
+ ata_pio_xfer(qc, page, offset, qc->sect_size);
+ }

qc->curbytes += qc->sect_size;
qc->cursg_ofs += qc->sect_size;
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