1 files changed, 85 insertions, 23 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 892662334be..6c5a70a7b57 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);