ext4: add a function merging extents right and left

1) Rename ext4_ext_try_to_merge() to ext4_ext_try_to_merge_right().

2) Add a new function ext4_ext_try_to_merge() which tries to merge
   an extent both left and right.

3) Use the new function in ext4_ext_convert_unwritten_endio() and
   ext4_ext_insert_extent().

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Tested-by: Allison Henderson <achender@linux.vnet.ibm.com>

1 files changed, 36 insertions, 29 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 4890d6f3ad15..23a98b6f00a2 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1563,7 +1563,7 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
  * Returns 0 if the extents (ex and ex+1) were _not_ merged and returns
  * 1 if they got merged.
  */
-static int ext4_ext_try_to_merge(struct inode *inode,
+static int ext4_ext_try_to_merge_right(struct inode *inode,
                                  struct ext4_ext_path *path,
                                  struct ext4_extent *ex)
 {
@@ -1603,6 +1603,31 @@ static int ext4_ext_try_to_merge(struct inode *inode,
 }
 
 /*
+ * This function tries to merge the @ex extent to neighbours in the tree.
+ * return 1 if merge left else 0.
+ */
+static int ext4_ext_try_to_merge(struct inode *inode,
+                                  struct ext4_ext_path *path,
+                                  struct ext4_extent *ex) {
+        struct ext4_extent_header *eh;
+        unsigned int depth;
+        int merge_done = 0;
+        int ret = 0;
+
+        depth = ext_depth(inode);
+        BUG_ON(path[depth].p_hdr == NULL);
+        eh = path[depth].p_hdr;
+
+        if (ex > EXT_FIRST_EXTENT(eh))
+                merge_done = ext4_ext_try_to_merge_right(inode, path, ex - 1);
+
+        if (!merge_done)
+                ret = ext4_ext_try_to_merge_right(inode, path, ex);
+
+        return ret;
+}
+
+/*
  * check if a portion of the "newext" extent overlaps with an
  * existing extent.
  *
@@ -3039,6 +3064,7 @@ fix_extent_len:
         ext4_ext_dirty(handle, inode, path + depth);
         return err;
 }
+
 static int ext4_convert_unwritten_extents_endio(handle_t *handle,
                                               struct inode *inode,
                                               struct ext4_ext_path *path)
@@ -3047,46 +3073,27 @@ static int ext4_convert_unwritten_extents_endio(handle_t *handle,
         struct ext4_extent_header *eh;
         int depth;
         int err = 0;
-        int ret = 0;
 
         depth = ext_depth(inode);
         eh = path[depth].p_hdr;
         ex = path[depth].p_ext;
 
+        ext_debug("ext4_convert_unwritten_extents_endio: inode %lu, logical"
+                "block %llu, max_blocks %u\n", inode->i_ino,
+                (unsigned long long)le32_to_cpu(ex->ee_block),
+                ext4_ext_get_actual_len(ex));
+
         err = ext4_ext_get_access(handle, inode, path + depth);
         if (err)
                 goto out;
         /* first mark the extent as initialized */
         ext4_ext_mark_initialized(ex);
 
-        /*
-         * We have to see if it can be merged with the extent
-         * on the left.
+        /* note: ext4_ext_correct_indexes() isn't needed here because
+         * borders are not changed
          */
-        if (ex > EXT_FIRST_EXTENT(eh)) {
-                /*
-                 * To merge left, pass "ex - 1" to try_to_merge(),
-                 * since it merges towards right _only_.
-                 */
-                ret = ext4_ext_try_to_merge(inode, path, ex - 1);
-                if (ret) {
-                        err = ext4_ext_correct_indexes(handle, inode, path);
-                        if (err)
-                                goto out;
-                        depth = ext_depth(inode);
-                        ex--;
-                }
-        }
-        /*
-         * Try to Merge towards right.
-         */
-        ret = ext4_ext_try_to_merge(inode, path, ex);
-        if (ret) {
-                err = ext4_ext_correct_indexes(handle, inode, path);
-                if (err)
-                        goto out;
-                depth = ext_depth(inode);
-        }
+        ext4_ext_try_to_merge(inode, path, ex);
+
         /* Mark modified extent as dirty */
         err = ext4_ext_dirty(handle, inode, path + depth);
 out: