[PATCH] mm: use __GFP_NOMEMALLOC

Use the new __GFP_NOMEMALLOC to simplify the previous handling of
PF_MEMALLOC.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 13 insertions, 33 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 77619a56e2bf..0dd6c2b5391b 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -331,25 +331,19 @@ crypt_alloc_buffer(struct crypt_config *cc, unsigned int size,
         struct bio *bio;
         unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
         int gfp_mask = GFP_NOIO | __GFP_HIGHMEM;
-        unsigned long flags = current->flags;
         unsigned int i;
 
         /*
-         * Tell VM to act less aggressively and fail earlier.
-         * This is not necessary but increases throughput.
+         * Use __GFP_NOMEMALLOC to tell the VM to act less aggressively and
+         * to fail earlier.  This is not necessary but increases throughput.
          * FIXME: Is this really intelligent?
          */
-        current->flags &= ~PF_MEMALLOC;
-
         if (base_bio)
-                bio = bio_clone(base_bio, GFP_NOIO);
+                bio = bio_clone(base_bio, GFP_NOIO|__GFP_NOMEMALLOC);
         else
-                bio = bio_alloc(GFP_NOIO, nr_iovecs);
-        if (!bio) {
-                if (flags & PF_MEMALLOC)
-                        current->flags |= PF_MEMALLOC;
+                bio = bio_alloc(GFP_NOIO|__GFP_NOMEMALLOC, nr_iovecs);
+        if (!bio)
                 return NULL;
-        }
 
         /* if the last bio was not complete, continue where that one ended */
         bio->bi_idx = *bio_vec_idx;
@@ -386,9 +380,6 @@ crypt_alloc_buffer(struct crypt_config *cc, unsigned int size,
                 size -= bv->bv_len;
         }
 
-        if (flags & PF_MEMALLOC)
-                current->flags |= PF_MEMALLOC;
-
         if (!bio->bi_size) {
                 bio_put(bio);
                 return NULL;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index a063a902ed03..4f251775ef90 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -143,7 +143,6 @@ void __delete_from_swap_cache(struct page *page)
 int add_to_swap(struct page * page)
 {
         swp_entry_t entry;
-        int pf_flags;
         int err;
 
         if (!PageLocked(page))
@@ -154,29 +153,19 @@ int add_to_swap(struct page * page)
                 if (!entry.val)
                         return 0;
 
-                /* Radix-tree node allocations are performing
-                 * GFP_ATOMIC allocations under PF_MEMALLOC.  
-                 * They can completely exhaust the page allocator.  
-                 *
-                 * So PF_MEMALLOC is dropped here.  This causes the slab 
-                 * allocations to fail earlier, so radix-tree nodes will 
-                 * then be allocated from the mempool reserves.
+                /*
+                 * Radix-tree node allocations from PF_MEMALLOC contexts could
+                 * completely exhaust the page allocator. __GFP_NOMEMALLOC
+                 * stops emergency reserves from being allocated.
                  *
-                 * We're still using __GFP_HIGH for radix-tree node
-                 * allocations, so some of the emergency pools are available,
-                 * just not all of them.
+                 * TODO: this could cause a theoretical memory reclaim
+                 * deadlock in the swap out path.
                  */
-
-                pf_flags = current->flags;
-                current->flags &= ~PF_MEMALLOC;
-
                 /*
                  * Add it to the swap cache and mark it dirty
                  */
-                err = __add_to_swap_cache(page, entry, GFP_ATOMIC|__GFP_NOWARN);
-
-                if (pf_flags & PF_MEMALLOC)
-                        current->flags |= PF_MEMALLOC;
+                err = __add_to_swap_cache(page, entry,
+                                GFP_ATOMIC|__GFP_NOMEMALLOC|__GFP_NOWARN);
 
                 switch (err) {
                 case 0:                         /* Success */