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vmscan: let GFP_NOFS go to swap again

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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: Hugh Dickins <hugh@veritas.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2008-11-19 15:36:37 -08:00 committed by Linus Torvalds
parent bda8550dee
commit 63eb6b93ce
1 changed files with 3 additions and 0 deletions
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3
mm/vmscan.c
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@ -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 */