On Mon, May 04, 2009 at 10:14:17AM +0100, Jan Beulich wrote:
> >@@ -329,11 +329,15 @@ static pte_t blktap_clear_pte(struct vm_
> > * If the address is before the start of the grant mapped region or
> > * if vm_file is NULL (meaning mmap failed and we have nothing to do)
> > */
> >- if (uvaddr < uvstart || vma->vm_file == NULL)
> >+ if (vma->vm_file != NULL) {
> >+ info = vma->vm_file->private_data;
> >+ uvstart = info->rings_vstart + (RING_PAGES << PAGE_SHIFT);
> >+ } else
> >+ uvstart = uvaddr; /* make the following if clause true */
> >+ if (uvaddr < uvstart)
> > return ptep_get_and_clear_full(vma->vm_mm, uvaddr,
> > ptep, is_fullmm);
>
> It would appear to me as if the comment and the code are out of sync:
> Assigning uvaddr to uvstart makes the if clause's condition false whenever
> vm->vm_file == NULL. According to how the old code worked, I'd say the
> code needs to be fixed, but I'm not certain, hence I'm hesitant to submit a
> patch...
You're quite right. Thank you for pointing out.
linux/blktap: fix blktap_clear_pte().
fix blktap_clear_pte(). In case of vma->vm_file == NULL
case wasn't handled correctly.
Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
diff --git a/drivers/xen/blktap/blktap.c b/drivers/xen/blktap/blktap.c
--- a/drivers/xen/blktap/blktap.c
+++ b/drivers/xen/blktap/blktap.c
@@ -314,7 +314,7 @@ static pte_t blktap_clear_pte(struct vm_
pte_t copy;
tap_blkif_t *info = NULL;
int offset, seg, usr_idx, pending_idx, mmap_idx;
- unsigned long uvstart;
+ unsigned long uvstart = 0;
unsigned long kvaddr;
struct page *pg;
struct grant_handle_pair *khandle;
@@ -328,9 +328,8 @@ static pte_t blktap_clear_pte(struct vm_
if (vma->vm_file != NULL) {
info = vma->vm_file->private_data;
uvstart = info->rings_vstart + (RING_PAGES << PAGE_SHIFT);
- } else
- uvstart = uvaddr; /* make the following if clause true */
- if (uvaddr < uvstart)
+ }
+ if (vma->vm_file == NULL || uvaddr < uvstart)
return ptep_get_and_clear_full(vma->vm_mm, uvaddr,
ptep, is_fullmm);
--
yamahata
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