Btrfs: add ref_count and free function for btrfs_bio

1: ref_count is simple than current RBIO_HOLD_BBIO_MAP_BIT flag
   to keep btrfs_bio's memory in raid56 recovery implement.
2: free function for bbio will make code clean and flexible, plus
   forced data type checking in compile.

Changelog v1->v2:
 Rename following by David Sterba's suggestion:
 put_btrfs_bio() -> btrfs_put_bio()
 get_btrfs_bio() -> btrfs_get_bio()
 bbio->ref_count -> bbio->refs

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 36 insertions, 7 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c0f1d524c371..0843bcd6304c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4901,6 +4901,37 @@ static void sort_parity_stripes(struct btrfs_bio *bbio, int num_stripes)
         }
 }
 
+static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
+{
+        struct btrfs_bio *bbio = kzalloc(
+                sizeof(struct btrfs_bio) +
+                sizeof(struct btrfs_bio_stripe) * (total_stripes) +
+                sizeof(int) * (real_stripes) +
+                sizeof(u64) * (real_stripes),
+                GFP_NOFS);
+        if (!bbio)
+                return NULL;
+
+        atomic_set(&bbio->error, 0);
+        atomic_set(&bbio->refs, 1);
+
+        return bbio;
+}
+
+void btrfs_get_bbio(struct btrfs_bio *bbio)
+{
+        WARN_ON(!atomic_read(&bbio->refs));
+        atomic_inc(&bbio->refs);
+}
+
+void btrfs_put_bbio(struct btrfs_bio *bbio)
+{
+        if (!bbio)
+                return;
+        if (atomic_dec_and_test(&bbio->refs))
+                kfree(bbio);
+}
+
 static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                              u64 logical, u64 *length,
                              struct btrfs_bio **bbio_ret,
@@ -5052,7 +5083,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                          * is not left of the left cursor
                          */
                         ret = -EIO;
-                        kfree(tmp_bbio);
+                        btrfs_put_bbio(tmp_bbio);
                         goto out;
                 }
 
@@ -5087,11 +5118,11 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                 } else {
                         WARN_ON(1);
                         ret = -EIO;
-                        kfree(tmp_bbio);
+                        btrfs_put_bbio(tmp_bbio);
                         goto out;
                 }
 
-                kfree(tmp_bbio);
+                btrfs_put_bbio(tmp_bbio);
         } else if (mirror_num > map->num_stripes) {
                 mirror_num = 0;
         }
@@ -5213,13 +5244,11 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                 tgtdev_indexes = num_stripes;
         }
 
-        bbio = kzalloc(btrfs_bio_size(num_alloc_stripes, tgtdev_indexes),
-                       GFP_NOFS);
+        bbio = alloc_btrfs_bio(num_alloc_stripes, tgtdev_indexes);
         if (!bbio) {
                 ret = -ENOMEM;
                 goto out;
         }
-        atomic_set(&bbio->error, 0);
         if (dev_replace_is_ongoing)
                 bbio->tgtdev_map = (int *)(bbio->stripes + num_alloc_stripes);
 
@@ -5558,7 +5587,7 @@ static inline void btrfs_end_bbio(struct btrfs_bio *bbio, struct bio *bio, int e
                 bio_endio_nodec(bio, err);
         else
                 bio_endio(bio, err);
-        kfree(bbio);
+        btrfs_put_bbio(bbio);
 }
 
 static void btrfs_end_bio(struct bio *bio, int err)