[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>

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;

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 */