1 files changed, 29 insertions, 14 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b7ddc77fa568..0d50d49d990a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2020,6 +2020,17 @@ struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
         return latest;
 }
 
+/*
+ * this should be called twice, once with wait == 0 and
+ * once with wait == 1.  When wait == 0 is done, all the buffer heads
+ * we write are pinned.
+ *
+ * They are released when wait == 1 is done.
+ * max_mirrors must be the same for both runs, and it indicates how
+ * many supers on this one device should be written.
+ *
+ * max_mirrors == 0 means to write them all.
+ */
 static int write_dev_supers(struct btrfs_device *device,
                             struct btrfs_super_block *sb,
                             int do_barriers, int wait, int max_mirrors)
@@ -2055,12 +2066,16 @@ static int write_dev_supers(struct btrfs_device *device,
                         bh = __find_get_block(device->bdev, bytenr / 4096,
                                               BTRFS_SUPER_INFO_SIZE);
                         BUG_ON(!bh);
-                        brelse(bh);
                         wait_on_buffer(bh);
-                        if (buffer_uptodate(bh)) {
-                                brelse(bh);
-                                continue;
-                        }
+                        if (!buffer_uptodate(bh))
+                                errors++;
+
+                        /* drop our reference */
+                        brelse(bh);
+
+                        /* drop the reference from the wait == 0 run */
+                        brelse(bh);
+                        continue;
                 } else {
                         btrfs_set_super_bytenr(sb, bytenr);
 
@@ -2071,12 +2086,18 @@ static int write_dev_supers(struct btrfs_device *device,
                                               BTRFS_CSUM_SIZE);
                         btrfs_csum_final(crc, sb->csum);
 
+                        /*
+                         * one reference for us, and we leave it for the
+                         * caller
+                         */
                         bh = __getblk(device->bdev, bytenr / 4096,
                                       BTRFS_SUPER_INFO_SIZE);
                         memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);
 
-                        set_buffer_uptodate(bh);
+                        /* one reference for submit_bh */
                         get_bh(bh);
+
+                        set_buffer_uptodate(bh);
                         lock_buffer(bh);
                         bh->b_end_io = btrfs_end_buffer_write_sync;
                 }
@@ -2088,6 +2109,7 @@ static int write_dev_supers(struct btrfs_device *device,
                                        device->name);
                                 set_buffer_uptodate(bh);
                                 device->barriers = 0;
+                                /* one reference for submit_bh */
                                 get_bh(bh);
                                 lock_buffer(bh);
                                 ret = submit_bh(WRITE_SYNC, bh);
@@ -2096,15 +2118,8 @@ static int write_dev_supers(struct btrfs_device *device,
                         ret = submit_bh(WRITE_SYNC, bh);
                 }
 
-                if (!ret && wait) {
-                        wait_on_buffer(bh);
-                        if (!buffer_uptodate(bh))
-                                errors++;
-                } else if (ret) {
+                if (ret)
                         errors++;
-                }
-                if (wait)
-                        brelse(bh);
         }
         return errors < i ? 0 : -1;
 }