On Mon, May 21 2007, Benny Halevy wrote:
> Jens Axboe wrote:
> > On Thu, May 10 2007, Benny Halevy wrote:
> >> @@ -411,12 +406,13 @@ int gart_map_sg(struct device *dev, struct 
> >> scatterlist *sg, int nents, int dir)
> >>                       boundary and the new one doesn't have an offset. */
> >>                    if (!iommu_merge || !nextneed || !need || s->offset ||
> >>                        (ps->offset + ps->length) % PAGE_SIZE) { 
> >> -                          if (dma_map_cont(sg, start, i, sg+out, pages,
> >> -                                           need) < 0)
> >> +                          if (dma_map_cont(start_sg, i - start, sg+out,
> >> +                                            pages, need) < 0)
> >>                                    goto error;
> >>                            out++;
> >>                            pages = 0;
> >> -                          start = i;      
> >> +                          start = i;
> >> +                          start_sg = s;
> >>                    }
> >>            }
> >>  
> >> @@ -424,7 +420,7 @@ int gart_map_sg(struct device *dev, struct scatterlist 
> >> *sg, int nents, int dir)
> >>            pages += to_pages(s->offset, s->length);
> >>            ps = s;
> >>    }
> >> -  if (dma_map_cont(sg, start, i, sg+out, pages, need) < 0)
> >> +  if (dma_map_cont(start_sg, i - start, sg+out, pages, need) < 0)
> >>            goto error;
> >>    out++;
> >>    flush_gart();
> > 
> > Your patch is (very) buggy, the whole premise of doing chained sg
> > entries makes sg + int illegal!
> > 
> 
> You're right.  I'll send a fix asap.

Did you see this one, I cooked it up after sending that mail out. Please
review :-)

diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 2e22a3a..b16384f 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -381,7 +381,7 @@ int gart_map_sg(struct device *dev, struct scatterlist *sg, 
int nents, int dir)
        int start;
        unsigned long pages = 0;
        int need = 0, nextneed;
-       struct scatterlist *s, *ps, *start_sg;
+       struct scatterlist *s, *ps, *start_sg, *sgmap;
 
        if (nents == 0) 
                return 0;
@@ -391,7 +391,7 @@ int gart_map_sg(struct device *dev, struct scatterlist *sg, 
int nents, int dir)
 
        out = 0;
        start = 0;
-       start_sg = sg;
+       start_sg = sgmap = sg;
        ps = NULL; /* shut up gcc */
        for_each_sg(sg, s, nents, i) {
                dma_addr_t addr = page_to_phys(s->page) + s->offset;
@@ -405,11 +405,12 @@ int gart_map_sg(struct device *dev, struct scatterlist 
*sg, int nents, int dir)
                        /* Can only merge when the last chunk ends on a page 
                           boundary and the new one doesn't have an offset. */
                        if (!iommu_merge || !nextneed || !need || s->offset ||
-                           (ps->offset + ps->length) % PAGE_SIZE) { 
-                               if (dma_map_cont(start_sg, i - start, sg+out,
+                           (ps->offset + ps->length) % PAGE_SIZE) {
+                               if (dma_map_cont(start_sg, i - start, sgmap,
                                                  pages, need) < 0)
                                        goto error;
                                out++;
+                               sgmap = sg_next(sgmap);
                                pages = 0;
                                start = i;
                                start_sg = s;
@@ -420,7 +421,7 @@ int gart_map_sg(struct device *dev, struct scatterlist *sg, 
int nents, int dir)
                pages += to_pages(s->offset, s->length);
                ps = s;
        }
-       if (dma_map_cont(start_sg, i - start, sg+out, pages, need) < 0)
+       if (dma_map_cont(start_sg, i - start, sgmap, pages, need) < 0)
                goto error;
        out++;
        flush_gart();

-- 
Jens Axboe

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