Btrfs, raid56: use a variant to record the operation type

We will introduce new operation type later, if we still use integer
variant as bool variant to record the operation type, we would add new
variant and increase the size of raid bio structure. It is not good,
by this patch, we define different number for different operation,
and we can just use a variant to record the operation type.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

fs/btrfs/raid56.c

@@ -69,6 +69,11 @@
 
 #define RBIO_CACHE_SIZE 1024
 
+enum btrfs_rbio_ops {
+	BTRFS_RBIO_WRITE	= 0,
+	BTRFS_RBIO_READ_REBUILD	= 1,
+};
+
 struct btrfs_raid_bio {
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_bio *bbio;
@@ -131,7 +136,7 @@ struct btrfs_raid_bio {
 	 * differently from a parity rebuild as part of
 	 * rmw
 	 */
-	int read_rebuild;
+	enum btrfs_rbio_ops operation;
 
 	/* first bad stripe */
 	int faila;
@@ -154,7 +159,6 @@ struct btrfs_raid_bio {
 
 	atomic_t refs;
 
-
 	atomic_t stripes_pending;
 
 	atomic_t error;
@@ -590,8 +594,7 @@ static int rbio_can_merge(struct btrfs_raid_bio *last,
 		return 0;
 
 	/* reads can't merge with writes */
-	if (last->read_rebuild !=
-	    cur->read_rebuild) {
+	if (last->operation != cur->operation) {
 		return 0;
 	}
 
@@ -784,9 +787,9 @@ static noinline void unlock_stripe(struct btrfs_raid_bio *rbio)
 			spin_unlock(&rbio->bio_list_lock);
 			spin_unlock_irqrestore(&h->lock, flags);
 
-			if (next->read_rebuild)
+			if (next->operation == BTRFS_RBIO_READ_REBUILD)
 				async_read_rebuild(next);
-			else {
+			else if (next->operation == BTRFS_RBIO_WRITE){
 				steal_rbio(rbio, next);
 				async_rmw_stripe(next);
 			}
@@ -1720,6 +1723,7 @@ int raid56_parity_write(struct btrfs_root *root, struct bio *bio,
 	}
 	bio_list_add(&rbio->bio_list, bio);
 	rbio->bio_list_bytes = bio->bi_iter.bi_size;
+	rbio->operation = BTRFS_RBIO_WRITE;
 
 	/*
 	 * don't plug on full rbios, just get them out the door
@@ -1768,7 +1772,7 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
 	faila = rbio->faila;
 	failb = rbio->failb;
 
-	if (rbio->read_rebuild) {
+	if (rbio->operation == BTRFS_RBIO_READ_REBUILD) {
 		spin_lock_irq(&rbio->bio_list_lock);
 		set_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
 		spin_unlock_irq(&rbio->bio_list_lock);
@@ -1785,7 +1789,7 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
 			 * if we're rebuilding a read, we have to use
 			 * pages from the bio list
 			 */
-			if (rbio->read_rebuild &&
+			if (rbio->operation == BTRFS_RBIO_READ_REBUILD &&
 			    (stripe == faila || stripe == failb)) {
 				page = page_in_rbio(rbio, stripe, pagenr, 0);
 			} else {
@@ -1878,7 +1882,7 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
 		 * know they can be trusted.  If this was a read reconstruction,
 		 * other endio functions will fiddle the uptodate bits
 		 */
-		if (!rbio->read_rebuild) {
+		if (rbio->operation == BTRFS_RBIO_WRITE) {
 			for (i = 0;  i < nr_pages; i++) {
 				if (faila != -1) {
 					page = rbio_stripe_page(rbio, faila, i);
@@ -1895,7 +1899,7 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
 			 * if we're rebuilding a read, we have to use
 			 * pages from the bio list
 			 */
-			if (rbio->read_rebuild &&
+			if (rbio->operation == BTRFS_RBIO_READ_REBUILD &&
 			    (stripe == faila || stripe == failb)) {
 				page = page_in_rbio(rbio, stripe, pagenr, 0);
 			} else {
@@ -1910,8 +1914,7 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
 	kfree(pointers);
 
 cleanup_io:
-
-	if (rbio->read_rebuild) {
+	if (rbio->operation == BTRFS_RBIO_READ_REBUILD) {
 		if (err == 0 &&
 		    !test_bit(RBIO_HOLD_BBIO_MAP_BIT, &rbio->flags))
 			cache_rbio_pages(rbio);
@@ -2050,7 +2053,7 @@ static int __raid56_parity_recover(struct btrfs_raid_bio *rbio)
 	return 0;
 
 cleanup:
-	if (rbio->read_rebuild)
+	if (rbio->operation == BTRFS_RBIO_READ_REBUILD)
 		rbio_orig_end_io(rbio, -EIO, 0);
 	return -EIO;
 }
@@ -2076,7 +2079,7 @@ int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
 
 	if (hold_bbio)
 		set_bit(RBIO_HOLD_BBIO_MAP_BIT, &rbio->flags);
-	rbio->read_rebuild = 1;
+	rbio->operation = BTRFS_RBIO_READ_REBUILD;
 	bio_list_add(&rbio->bio_list, bio);
 	rbio->bio_list_bytes = bio->bi_iter.bi_size;