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Subject[PATCH] mm: shmem: use proper gfp flags for shmem_writepage()
Date
The shmem_writepage() uses GFP_ATOMIC to allocate swap cache.
GFP_ATOMIC used to mean __GFP_HIGH, but now it means __GFP_HIGH |
__GFP_ATOMIC | __GFP_KSWAPD_RECLAIM. However, shmem_writepage() should
write out to swap only in response to memory pressure, so
__GFP_KSWAPD_RECLAIM looks useless since the caller may be kswapd itself
or in direct reclaim already.

In addition, XArray node allocations from PF_MEMALLOC contexts could
completely exhaust the page allocator, __GFP_NOMEMALLOC stops emergency
reserves from being allocated.

Here just copy the gfp flags used by add_to_swap().

Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
mm/shmem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 220be9f..9691dec 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1369,7 +1369,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
if (list_empty(&info->swaplist))
list_add(&info->swaplist, &shmem_swaplist);

- if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
+ if (add_to_swap_cache(page, swap,
+ __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN) == 0) {
spin_lock_irq(&info->lock);
shmem_recalc_inode(inode);
info->swapped++;
--
1.8.3.1
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