btrfs: pass NOWAIT for set/clear extent bits as another bit

The only flags we now pass to set_extent_bit/__clear_extent_bit are
GFP_NOFS and GFP_NOWAIT (a few functions handling mappings). This
requires an extra parameter to be passed everywhere but is almost always
the same.

Encode the GFP_NOWAIT as an artificial extent bit and extract the
real bits and gfp mask in the lowest level helpers. Now the passed
gfp mask is not actually used and can be removed.
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-io-tree.c

@@ -532,6 +532,16 @@ static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
 	return next;
 }
 
+/*
+ * Detect if extent bits request NOWAIT semantics and set the gfp mask accordingly,
+ * unset the EXTENT_NOWAIT bit.
+ */
+static void set_gfp_mask_from_bits(u32 *bits, gfp_t *mask)
+{
+	*mask = (*bits & EXTENT_NOWAIT ? GFP_NOWAIT : GFP_NOFS);
+	*bits &= EXTENT_NOWAIT - 1;
+}
+
 /*
  * Clear some bits on a range in the tree.  This may require splitting or
  * inserting elements in the tree, so the gfp mask is used to indicate which
@@ -557,6 +567,7 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 	int wake;
 	int delete = (bits & EXTENT_CLEAR_ALL_BITS);
 
+	set_gfp_mask_from_bits(&bits, &mask);
 	btrfs_debug_check_extent_io_range(tree, start, end);
 	trace_btrfs_clear_extent_bit(tree, start, end - start + 1, bits);
 
@@ -979,6 +990,7 @@ static int __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 	u64 last_end;
 	u32 exclusive_bits = (bits & EXTENT_LOCKED);
 
+	set_gfp_mask_from_bits(&bits, &mask);
 	btrfs_debug_check_extent_io_range(tree, start, end);
 	trace_btrfs_set_extent_bit(tree, start, end - start + 1, bits);
 

fs/btrfs/extent-io-tree.h

@@ -43,6 +43,15 @@ enum {
 	 * want the extent states to go away.
 	 */
 	ENUM_BIT(EXTENT_CLEAR_ALL_BITS),
+
+	/*
+	 * This must be last.
+	 *
+	 * Bit not representing a state but a request for NOWAIT semantics,
+	 * e.g. when allocating memory, and must be masked out from the other
+	 * bits.
+	 */
+	ENUM_BIT(EXTENT_NOWAIT)
 };
 
 #define EXTENT_DO_ACCOUNTING    (EXTENT_CLEAR_META_RESV | \

fs/btrfs/extent_map.c

@@ -365,8 +365,8 @@ static void extent_map_device_set_bits(struct extent_map *em, unsigned bits)
 		struct btrfs_device *device = stripe->dev;
 
 		set_extent_bit(&device->alloc_state, stripe->physical,
-			       stripe->physical + stripe_size - 1, bits, NULL,
-			       GFP_NOWAIT);
+			       stripe->physical + stripe_size - 1,
+			       bits | EXTENT_NOWAIT, NULL, GFP_NOWAIT);
 	}
 }
 
@@ -381,7 +381,8 @@ static void extent_map_device_clear_bits(struct extent_map *em, unsigned bits)
 		struct btrfs_device *device = stripe->dev;
 
 		__clear_extent_bit(&device->alloc_state, stripe->physical,
-				   stripe->physical + stripe_size - 1, bits,
+				   stripe->physical + stripe_size - 1,
+				   bits | EXTENT_NOWAIT,
 				   NULL, GFP_NOWAIT, NULL);
 	}
 }

fs/btrfs/zoned.c

@@ -1612,7 +1612,7 @@ void btrfs_redirty_list_add(struct btrfs_transaction *trans,
 	set_bit(EXTENT_BUFFER_NO_CHECK, &eb->bflags);
 	set_extent_buffer_dirty(eb);
 	set_extent_bit(&trans->dirty_pages, eb->start, eb->start + eb->len - 1,
-			EXTENT_DIRTY, NULL, GFP_NOWAIT);
+			EXTENT_DIRTY | EXTENT_NOWAIT, NULL, GFP_NOWAIT);
 }
 
 bool btrfs_use_zone_append(struct btrfs_bio *bbio)