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authorYang Shi <shy828301@gmail.com>2021-06-30 18:52:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-30 20:47:30 -0700
commit1fb08ac63beedf58e2ae9f229ea1f9474949a185 (patch)
tree4ee1596e310b4f55e35e490eff6f7488bcb54bb0 /mm/rmap.c
parentcebc774fdc9cb39b959968fbfd7aabe7a8a5154c (diff)
downloadlinux-1fb08ac63beedf58e2ae9f229ea1f9474949a185.tar.bz2
mm: rmap: make try_to_unmap() void function
Currently try_to_unmap() return bool value by checking page_mapcount(), however this may return false positive since page_mapcount() doesn't check all subpages of compound page. The total_mapcount() could be used instead, but its cost is higher since it traverses all subpages. Actually the most callers of try_to_unmap() don't care about the return value at all. So just need check if page is still mapped by page_mapped() when necessary. And page_mapped() does bail out early when it finds mapped subpage. Link: https://lkml.kernel.org/r/bb27e3fe-6036-b637-5086-272befbfe3da@google.com Suggested-by: Hugh Dickins <hughd@google.com> Signed-off-by: Yang Shi <shy828301@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Jan Kara <jack@suse.cz> Cc: Jue Wang <juew@google.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Peter Xu <peterx@redhat.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Wang Yugui <wangyugui@e16-tech.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c15
1 files changed, 4 insertions, 11 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index e05c300048e6..f9fd5bc54f0a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1405,7 +1405,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
/*
* When racing against e.g. zap_pte_range() on another cpu,
* in between its ptep_get_and_clear_full() and page_remove_rmap(),
- * try_to_unmap() may return false when it is about to become true,
+ * try_to_unmap() may return before page_mapped() has become false,
* if page table locking is skipped: use TTU_SYNC to wait for that.
*/
if (flags & TTU_SYNC)
@@ -1756,9 +1756,10 @@ static int page_not_mapped(struct page *page)
* Tries to remove all the page table entries which are mapping this
* page, used in the pageout path. Caller must hold the page lock.
*
- * If unmap is successful, return true. Otherwise, false.
+ * It is the caller's responsibility to check if the page is still
+ * mapped when needed (use TTU_SYNC to prevent accounting races).
*/
-bool try_to_unmap(struct page *page, enum ttu_flags flags)
+void try_to_unmap(struct page *page, enum ttu_flags flags)
{
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
@@ -1783,14 +1784,6 @@ bool try_to_unmap(struct page *page, enum ttu_flags flags)
rmap_walk_locked(page, &rwc);
else
rmap_walk(page, &rwc);
-
- /*
- * When racing against e.g. zap_pte_range() on another cpu,
- * in between its ptep_get_and_clear_full() and page_remove_rmap(),
- * try_to_unmap() may return false when it is about to become true,
- * if page table locking is skipped: use TTU_SYNC to wait for that.
- */
- return !page_mapcount(page);
}
/**