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SubjectRe: 2.4.21-pre3 kernel crash
On Mon, Jan 27 2003, Martin MOKREJ? wrote:
> On Mon, 27 Jan 2003, Ross Biro wrote:
>
> > This looks like the same problem I ran into with IDE and highmem not
> > getting along. Try compiling your kernel with out highmem enabled and
> > see what happenes.
>
> Yes, that "fixes" it. Any "better solution"? ;-)
>
> > >Trace; c024dfc1 <ide_build_sglist+181/1a0>
> > >Trace; c024e1b4 <ide_build_dmatable+54/1a0>
> > >Trace; c024e6df <__ide_dma_read+3f/150>

Someone completely lost the highmem capable scatterlist setup, *boggle*.
This should fix it.

===== drivers/ide/ide-dma.c 1.7 vs edited =====
--- 1.7/drivers/ide/ide-dma.c Wed Nov 20 18:46:24 2002
+++ edited/drivers/ide/ide-dma.c Mon Jan 27 20:22:06 2003
@@ -249,6 +249,7 @@
{
struct buffer_head *bh;
struct scatterlist *sg = hwif->sg_table;
+ unsigned long lastdataend = ~0UL;
int nents = 0;

if (hwif->sg_dma_active)
@@ -256,22 +257,28 @@

bh = rq->bh;
do {
- unsigned char *virt_addr = bh->b_data;
- unsigned int size = bh->b_size;
+ if (bh_phys(bh) == lastdataend) {
+ sg[nents - 1].length += bh->b_size;
+ lastdataend += bh->b_size;
+ continue;
+ }

if (nents >= PRD_ENTRIES)
return 0;

- while ((bh = bh->b_reqnext) != NULL) {
- if ((virt_addr + size) != (unsigned char *) bh->b_data)
- break;
- size += bh->b_size;
- }
memset(&sg[nents], 0, sizeof(*sg));
- sg[nents].address = virt_addr;
- sg[nents].length = size;
- if(size == 0)
- BUG();
+ if (bh->b_page) {
+ sg[nents].page = bh->b_page;
+ sg[nents].offset = bh_offset(bh);
+ } else {
+ if (((unsigned long) bh->b_data) < PAGE_SIZE)
+ BUG();
+
+ sg[nents].address = bh->b_data;
+ }
+
+ sg[nents].length = bh->b_size;
+ lastdataend = bh_phys(bh) + bh->b_size;
nents++;
} while (bh != NULL);

--
Jens Axboe

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