1 files changed, 85 insertions, 23 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 892662334be9..6c5a70a7b573 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1813,39 +1813,101 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
         }
         depth = ext_depth(inode);
         ex = path[depth].p_ext;
+        eh = path[depth].p_hdr;
         if (unlikely(path[depth].p_hdr == NULL)) {
                 EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
                 return -EIO;
         }
 
         /* try to insert block into found extent and return */
-        if (ex && !(flag & EXT4_GET_BLOCKS_PRE_IO)
-                && ext4_can_extents_be_merged(inode, ex, newext)) {
-                ext_debug("append [%d]%d block to %u:[%d]%d (from %llu)\n",
-                          ext4_ext_is_uninitialized(newext),
-                          ext4_ext_get_actual_len(newext),
-                          le32_to_cpu(ex->ee_block),
-                          ext4_ext_is_uninitialized(ex),
-                          ext4_ext_get_actual_len(ex),
-                          ext4_ext_pblock(ex));
-                err = ext4_ext_get_access(handle, inode, path + depth);
-                if (err)
-                        return err;
+        if (ex && !(flag & EXT4_GET_BLOCKS_PRE_IO)) {
 
                 /*
-                 * ext4_can_extents_be_merged should have checked that either
-                 * both extents are uninitialized, or both aren't. Thus we
-                 * need to check only one of them here.
+                 * Try to see whether we should rather test the extent on
+                 * right from ex, or from the left of ex. This is because
+                 * ext4_ext_find_extent() can return either extent on the
+                 * left, or on the right from the searched position. This
+                 * will make merging more effective.
                  */
-                if (ext4_ext_is_uninitialized(ex))
-                        uninitialized = 1;
-                ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
+                if (ex < EXT_LAST_EXTENT(eh) &&
+                    (le32_to_cpu(ex->ee_block) +
+                    ext4_ext_get_actual_len(ex) <
+                    le32_to_cpu(newext->ee_block))) {
+                        ex += 1;
+                        goto prepend;
+                } else if ((ex > EXT_FIRST_EXTENT(eh)) &&
+                           (le32_to_cpu(newext->ee_block) +
+                           ext4_ext_get_actual_len(newext) <
+                           le32_to_cpu(ex->ee_block)))
+                        ex -= 1;
+
+                /* Try to append newex to the ex */
+                if (ext4_can_extents_be_merged(inode, ex, newext)) {
+                        ext_debug("append [%d]%d block to %u:[%d]%d"
+                                  "(from %llu)\n",
+                                  ext4_ext_is_uninitialized(newext),
+                                  ext4_ext_get_actual_len(newext),
+                                  le32_to_cpu(ex->ee_block),
+                                  ext4_ext_is_uninitialized(ex),
+                                  ext4_ext_get_actual_len(ex),
+                                  ext4_ext_pblock(ex));
+                        err = ext4_ext_get_access(handle, inode,
+                                                  path + depth);
+                        if (err)
+                                return err;
+
+                        /*
+                         * ext4_can_extents_be_merged should have checked
+                         * that either both extents are uninitialized, or
+                         * both aren't. Thus we need to check only one of
+                         * them here.
+                         */
+                        if (ext4_ext_is_uninitialized(ex))
+                                uninitialized = 1;
+                        ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                         + ext4_ext_get_actual_len(newext));
-                if (uninitialized)
-                        ext4_ext_mark_uninitialized(ex);
-                eh = path[depth].p_hdr;
-                nearex = ex;
-                goto merge;
+                        if (uninitialized)
+                                ext4_ext_mark_uninitialized(ex);
+                        eh = path[depth].p_hdr;
+                        nearex = ex;
+                        goto merge;
+                }
+
+prepend:
+                /* Try to prepend newex to the ex */
+                if (ext4_can_extents_be_merged(inode, newext, ex)) {
+                        ext_debug("prepend %u[%d]%d block to %u:[%d]%d"
+                                  "(from %llu)\n",
+                                  le32_to_cpu(newext->ee_block),
+                                  ext4_ext_is_uninitialized(newext),
+                                  ext4_ext_get_actual_len(newext),
+                                  le32_to_cpu(ex->ee_block),
+                                  ext4_ext_is_uninitialized(ex),
+                                  ext4_ext_get_actual_len(ex),
+                                  ext4_ext_pblock(ex));
+                        err = ext4_ext_get_access(handle, inode,
+                                                  path + depth);
+                        if (err)
+                                return err;
+
+                        /*
+                         * ext4_can_extents_be_merged should have checked
+                         * that either both extents are uninitialized, or
+                         * both aren't. Thus we need to check only one of
+                         * them here.
+                         */
+                        if (ext4_ext_is_uninitialized(ex))
+                                uninitialized = 1;
+                        ex->ee_block = newext->ee_block;
+                        ext4_ext_store_pblock(ex, ext4_ext_pblock(newext));
+                        ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
+                                        + ext4_ext_get_actual_len(newext));
+                        if (uninitialized)
+                                ext4_ext_mark_uninitialized(ex);
+                        eh = path[depth].p_hdr;
+                        nearex = ex;
+                        goto merge;
+                }
         }
 
         depth = ext_depth(inode);