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Commit 63eb6b93 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

vmscan: let GFP_NOFS go to swap again 



In the past, GFP_NOFS (but of course not GFP_NOIO) was allowed to reclaim
by writing to swap.  That got partially broken in 2.6.23, when may_enter_fs
initialization was moved up before the allocation of swap, so its
PageSwapCache test was failing the first time around,

Fix it by setting may_enter_fs when add_to_swap() succeeds with
__GFP_IO.  In fact, check __GFP_IO before calling add_to_swap():
allocating swap we're not ready to use just increases disk seeking.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bda8550d

mm/vmscan.c

+3 −0
Original line number Diff line number Diff line
@@ -623,6 +623,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
		 * Try to allocate it some swap space here.

		 */

		if (PageAnon(page) && !PageSwapCache(page)) {

			if (!(sc->gfp_mask & __GFP_IO))

				goto keep_locked;

			switch (try_to_munlock(page)) {

			case SWAP_FAIL:		/* shouldn't happen */

			case SWAP_AGAIN:
@@ -634,6 +636,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
			}

			if (!add_to_swap(page, GFP_ATOMIC))

				goto activate_locked;

			may_enter_fs = 1;

		}

#endif /* CONFIG_SWAP */