The patch titled
swapin: fix valid_swaphandles defect
has been added to the -mm tree. Its filename is
swapin-fix-valid_swaphandles-defect.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: swapin: fix valid_swaphandles defect
From: Hugh Dickins <hugh@xxxxxxxxxxx>
valid_swaphandles is supposed to do a quick pass over the swap map entries
neigbouring the entry which swapin_readahead is targetting, to determine for
it a range worth reading all together. But since it always starts its search
from the beginning of the swap "cluster", a reject (free entry) there
immediately curtails the readaround, and every swapin_readahead from that
cluster is for just a single page. Instead scan forwards and backwards around
the target entry.
Use better names for some variables: a swap_info pointer is usually called
"si" not "swapdev". And at the end, if only the target page should be read,
return count of 0 to disable readaround, to avoid the unnecessarily repeated
call to read_swap_cache_async.
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 49 ++++++++++++++++++++++++++++++++----------------
1 file changed, 33 insertions(+), 16 deletions(-)
diff -puN mm/swapfile.c~swapin-fix-valid_swaphandles-defect mm/swapfile.c
--- a/mm/swapfile.c~swapin-fix-valid_swaphandles-defect
+++ a/mm/swapfile.c
@@ -1769,31 +1769,48 @@ get_swap_info_struct(unsigned type)
*/
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
+ struct swap_info_struct *si;
int our_page_cluster = page_cluster;
- int ret = 0, i = 1 << our_page_cluster;
- unsigned long toff;
- struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
+ pgoff_t target, toff;
+ pgoff_t base, end;
+ int nr_pages = 0;
if (!our_page_cluster) /* no readahead */
return 0;
- toff = (swp_offset(entry) >> our_page_cluster) << our_page_cluster;
- if (!toff) /* first page is swap header */
- toff++, i--;
- *offset = toff;
+
+ si = &swap_info[swp_type(entry)];
+ target = swp_offset(entry);
+ base = (target >> our_page_cluster) << our_page_cluster;
+ end = base + (1 << our_page_cluster);
+ if (!base) /* first page is swap header */
+ base++;
spin_lock(&swap_lock);
- do {
- /* Don't read-ahead past the end of the swap area */
- if (toff >= swapdev->max)
+ if (end > si->max) /* don't go beyond end of map */
+ end = si->max;
+
+ /* Count contiguous allocated slots above our target */
+ for (toff = target; ++toff < end; nr_pages++) {
+ /* Don't read in free or bad pages */
+ if (!si->swap_map[toff])
break;
+ if (si->swap_map[toff] == SWAP_MAP_BAD)
+ break;
+ }
+ /* Count contiguous allocated slots below our target */
+ for (toff = target; --toff >= base; nr_pages++) {
/* Don't read in free or bad pages */
- if (!swapdev->swap_map[toff])
+ if (!si->swap_map[toff])
break;
- if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
+ if (si->swap_map[toff] == SWAP_MAP_BAD)
break;
- toff++;
- ret++;
- } while (--i);
+ }
spin_unlock(&swap_lock);
- return ret;
+
+ /*
+ * Indicate starting offset, and return number of pages to get:
+ * if only 1, say 0, since there's then no readahead to be done.
+ */
+ *offset = ++toff;
+ return nr_pages? ++nr_pages: 0;
}
_
Patches currently in -mm which might be from hugh@xxxxxxxxxxx are
origin.patch
exportfs-add-fid-type.patch
exportfs-add-new-methods.patch
shmem-new-export-ops.patch
exportfs-remove-old-methods.patch
exportfs-make-struct-export_operations-const.patch
exportfs-update-documentation.patch
fix-mprotect-vma_wants_writenotify-prot.patch
swapin_readahead-excise-numa-bogosity.patch
swapin_readahead-move-and-rearrange-args.patch
swapin-needs-gfp_mask-for-loop-on-tmpfs.patch
shmem-sgp_quick-and-sgp_fault-redundant.patch
shmem_getpage-return-page-locked.patch
shmem_file_write-is-redundant.patch
swapin-fix-valid_swaphandles-defect.patch
memory-controller-memory-accounting-v7.patch
prio_tree-debugging-patch.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
