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authorHuang Ying <ying.huang@intel.com>2017-09-07 02:22:19 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-07 03:27:27 +0300
commitba3c4ce6def4915093be80585ff69f780630f32f (patch)
tree3fa890d652981cc54c5ebd7ea59cfc134fad4a6c /mm/swapfile.c
parente07098294adfd03d582af7626752255e3d170393 (diff)
downloadlinux-ba3c4ce6def4915093be80585ff69f780630f32f.tar.xz
mm, THP, swap: make reuse_swap_page() works for THP swapped out
After supporting to delay THP (Transparent Huge Page) splitting after swapped out, it is possible that some page table mappings of the THP are turned into swap entries. So reuse_swap_page() need to check the swap count in addition to the map count as before. This patch done that. In the huge PMD write protect fault handler, in addition to the page map count, the swap count need to be checked too, so the page lock need to be acquired too when calling reuse_swap_page() in addition to the page table lock. [ying.huang@intel.com: silence a compiler warning] Link: http://lkml.kernel.org/r/87bmnzizjy.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20170724051840.2309-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c102
1 files changed, 93 insertions, 9 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 164d9624d7d2..2bfbfb87123a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1405,9 +1405,89 @@ static bool page_swapped(struct page *page)
return swap_page_trans_huge_swapped(si, entry);
return false;
}
+
+static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
+ int *total_swapcount)
+{
+ int i, map_swapcount, _total_mapcount, _total_swapcount;
+ unsigned long offset = 0;
+ struct swap_info_struct *si;
+ struct swap_cluster_info *ci = NULL;
+ unsigned char *map = NULL;
+ int mapcount, swapcount = 0;
+
+ /* hugetlbfs shouldn't call it */
+ VM_BUG_ON_PAGE(PageHuge(page), page);
+
+ if (likely(!PageTransCompound(page))) {
+ mapcount = atomic_read(&page->_mapcount) + 1;
+ if (total_mapcount)
+ *total_mapcount = mapcount;
+ if (PageSwapCache(page))
+ swapcount = page_swapcount(page);
+ if (total_swapcount)
+ *total_swapcount = swapcount;
+ return mapcount + swapcount;
+ }
+
+ page = compound_head(page);
+
+ _total_mapcount = _total_swapcount = map_swapcount = 0;
+ if (PageSwapCache(page)) {
+ swp_entry_t entry;
+
+ entry.val = page_private(page);
+ si = _swap_info_get(entry);
+ if (si) {
+ map = si->swap_map;
+ offset = swp_offset(entry);
+ }
+ }
+ if (map)
+ ci = lock_cluster(si, offset);
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ mapcount = atomic_read(&page[i]._mapcount) + 1;
+ _total_mapcount += mapcount;
+ if (map) {
+ swapcount = swap_count(map[offset + i]);
+ _total_swapcount += swapcount;
+ }
+ map_swapcount = max(map_swapcount, mapcount + swapcount);
+ }
+ unlock_cluster(ci);
+ if (PageDoubleMap(page)) {
+ map_swapcount -= 1;
+ _total_mapcount -= HPAGE_PMD_NR;
+ }
+ mapcount = compound_mapcount(page);
+ map_swapcount += mapcount;
+ _total_mapcount += mapcount;
+ if (total_mapcount)
+ *total_mapcount = _total_mapcount;
+ if (total_swapcount)
+ *total_swapcount = _total_swapcount;
+
+ return map_swapcount;
+}
#else
#define swap_page_trans_huge_swapped(si, entry) swap_swapcount(si, entry)
#define page_swapped(page) (page_swapcount(page) != 0)
+
+static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
+ int *total_swapcount)
+{
+ int mapcount, swapcount = 0;
+
+ /* hugetlbfs shouldn't call it */
+ VM_BUG_ON_PAGE(PageHuge(page), page);
+
+ mapcount = page_trans_huge_mapcount(page, total_mapcount);
+ if (PageSwapCache(page))
+ swapcount = page_swapcount(page);
+ if (total_swapcount)
+ *total_swapcount = swapcount;
+ return mapcount + swapcount;
+}
#endif
/*
@@ -1416,23 +1496,27 @@ static bool page_swapped(struct page *page)
* on disk will never be read, and seeking back there to write new content
* later would only waste time away from clustering.
*
- * NOTE: total_mapcount should not be relied upon by the caller if
+ * NOTE: total_map_swapcount should not be relied upon by the caller if
* reuse_swap_page() returns false, but it may be always overwritten
* (see the other implementation for CONFIG_SWAP=n).
*/
-bool reuse_swap_page(struct page *page, int *total_mapcount)
+bool reuse_swap_page(struct page *page, int *total_map_swapcount)
{
- int count;
+ int count, total_mapcount, total_swapcount;
VM_BUG_ON_PAGE(!PageLocked(page), page);
if (unlikely(PageKsm(page)))
return false;
- count = page_trans_huge_mapcount(page, total_mapcount);
- if (count <= 1 && PageSwapCache(page)) {
- count += page_swapcount(page);
- if (count != 1)
- goto out;
+ count = page_trans_huge_map_swapcount(page, &total_mapcount,
+ &total_swapcount);
+ if (total_map_swapcount)
+ *total_map_swapcount = total_mapcount + total_swapcount;
+ if (count == 1 && PageSwapCache(page) &&
+ (likely(!PageTransCompound(page)) ||
+ /* The remaining swap count will be freed soon */
+ total_swapcount == page_swapcount(page))) {
if (!PageWriteback(page)) {
+ page = compound_head(page);
delete_from_swap_cache(page);
SetPageDirty(page);
} else {
@@ -1448,7 +1532,7 @@ bool reuse_swap_page(struct page *page, int *total_mapcount)
spin_unlock(&p->lock);
}
}
-out:
+
return count <= 1;
}