William Lee Irwin III wrote:
>
> On Fri, Sep 27, 2002 at 10:54:54PM -0700, Andrew Morton wrote:
> > A simple fix would be to drop the atomic kmap of the source pte
> > and take it again after the alloc_one_pte_map() call.
> > Can you think of a more efficient way?
>
> Not one that isn't highly invasive, no. This is what I had in mind
> for the easy fix.
>
OK. kmap_atomics are pretty darn quick, but it might be better
to take a peek to see if the pgd and pmd are present, and only
drop the kmap if not.
Care to eyeball this? I haven't tested it yet.
mm/mremap.c | 25 +++++++++++++++++++++++++
1 files changed, 25 insertions(+)
--- 2.5.39/mm/mremap.c~move_one_page_fix Fri Sep 27 22:59:04 2002
+++ 2.5.39-akpm/mm/mremap.c Fri Sep 27 23:05:16 2002
@@ -53,6 +53,20 @@ end:
return pte;
}
+static inline int page_table_present(struct mm_struct *mm, unsigned long addr)
+{
+ pgd_t *pgd;
+ pmd_t *pmd;
+
+ pgd = pgd_offset(mm, addr);
+ if (pgd_none(*pgd))
+ return 0;
+ pmd = pmd_offset(pgd, addr);
+ if (pmd == NULL)
+ return 0;
+ return 1;
+}
+
static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr)
{
pmd_t * pmd;
@@ -98,7 +112,18 @@ static int move_one_page(struct vm_area_
spin_lock(&mm->page_table_lock);
src = get_one_pte_map_nested(mm, old_addr);
if (src) {
+ /*
+ * Look to see whether alloc_one_pte_map needs to perform a
+ * memory allocation. If it does then we need to drop the
+ * atomic kmap
+ */
+ if (!page_table_present(mm, new_addr)) {
+ pte_unmap_nested(src);
+ src = NULL;
+ }
dst = alloc_one_pte_map(mm, new_addr);
+ if (src == NULL)
+ src = get_one_pte_map_nested(mm, old_addr);
error = copy_one_pte(mm, src, dst);
pte_unmap_nested(src);
pte_unmap(dst);
.
-
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This archive was generated by hypermail 2b29 : Mon Sep 30 2002 - 22:00:35 EST