4 files changed, 26 insertions, 3 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 1fe82cfc1d93..ac606f076eb7 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -203,6 +203,8 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
                         em->block_start = merge->block_start;
                         merge->in_tree = 0;
                         if (merge->generation > em->generation) {
+                                em->mod_start = em->start;
+                                em->mod_len = em->len;
                                 em->generation = merge->generation;
                                 list_move(&em->list, &tree->modified_extents);
                         }
@@ -222,6 +224,7 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
                 rb_erase(&merge->rb_node, &tree->map);
                 merge->in_tree = 0;
                 if (merge->generation > em->generation) {
+                        em->mod_len = em->len;
                         em->generation = merge->generation;
                         list_move(&em->list, &tree->modified_extents);
                 }
@@ -247,6 +250,7 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
 {
         int ret = 0;
         struct extent_map *em;
+        bool prealloc = false;
 
         write_lock(&tree->lock);
         em = lookup_extent_mapping(tree, start, len);
@@ -259,8 +263,21 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
         list_move(&em->list, &tree->modified_extents);
         em->generation = gen;
         clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+        em->mod_start = em->start;
+        em->mod_len = em->len;
+
+        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
+                prealloc = true;
+                clear_bit(EXTENT_FLAG_PREALLOC, &em->flags);
+        }
 
         try_merge_map(tree, em);
+
+        if (prealloc) {
+                em->mod_start = em->start;
+                em->mod_len = em->len;
+        }
+
         free_extent_map(em);
 out:
         write_unlock(&tree->lock);
@@ -298,6 +315,9 @@ int add_extent_mapping(struct extent_map_tree *tree,
         }
         atomic_inc(&em->refs);
 
+        em->mod_start = em->start;
+        em->mod_len = em->len;
+
         try_merge_map(tree, em);
 out:
         return ret;
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 2388a60bd6e3..8e6294b51357 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -20,6 +20,8 @@ struct extent_map {
         /* all of these are in bytes */
         u64 start;
         u64 len;
+        u64 mod_start;
+        u64 mod_len;
         u64 orig_start;
         u64 block_start;
         u64 block_len;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ca4fa05171ab..878116d9625d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1308,6 +1308,7 @@ out_check:
                         em->block_start = disk_bytenr;
                         em->bdev = root->fs_info->fs_devices->latest_bdev;
                         set_bit(EXTENT_FLAG_PINNED, &em->flags);
+                        set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
                         while (1) {
                                 write_lock(&em_tree->lock);
                                 ret = add_extent_mapping(em_tree, em);
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 58075d711d24..71e71539ffb7 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2833,8 +2833,8 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
         struct btrfs_root *log = root->log_root;
         struct btrfs_file_extent_item *fi;
         struct btrfs_key key;
-        u64 start = em->start;
-        u64 len = em->len;
+        u64 start = em->mod_start;
+        u64 len = em->mod_len;
         u64 num_bytes;
         int nritems;
         int ret;
@@ -2970,7 +2970,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
                  * sequential then we need to copy the items we have and redo
                  * our search
                  */
-                if (args.nr && em->start != args.next_offset) {
+                if (args.nr && em->mod_start != args.next_offset) {
                         ret = copy_items(trans, log, dst_path, args.src,
                                          args.start_slot, args.nr,
                                          LOG_INODE_ALL);