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mm: shmem: use proper gfp flags for shmem_writepage() 

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().

Hugh:
 "a cleanup to make the two calls look the same when they don't need to
  be different (whereas the call from __read_swap_cache_async() rightly
  uses a lower priority gfp)".

Link: http://lkml.kernel.org/r/1572991351-86061-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yang Shi 2019-11-30 17:58:07 -08:00 committed by Linus Torvalds
parent 26083eb6b1
commit 4afab1cd25
1 changed files with 2 additions and 1 deletions
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3
mm/shmem.c
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@ -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++;