1 files changed, 89 insertions, 46 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 2352467..8926623 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3153,29 +3153,28 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 	struct ext4_extent_header *eh;
 	struct ext4_map_blocks split_map;
 	struct ext4_extent zero_ex;
-	struct ext4_extent *ex;
+	struct ext4_extent *ex, *abut_ex;
 	ext4_lblk_t ee_block, eof_block;
-	unsigned int ee_len, depth;
-	int allocated, max_zeroout = 0;
+	unsigned int ee_len, depth, map_len = map->m_len;
+	int allocated = 0, max_zeroout = 0;
 	int err = 0;
 	int split_flag = 0;
 
 	ext_debug("ext4_ext_convert_to_initialized: inode %lu, logical"
 		"block %llu, max_blocks %u\n", inode->i_ino,
-		(unsigned long long)map->m_lblk, map->m_len);
+		(unsigned long long)map->m_lblk, map_len);
 
 	sbi = EXT4_SB(inode->i_sb);
 	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
 		inode->i_sb->s_blocksize_bits;
-	if (eof_block < map->m_lblk + map->m_len)
-		eof_block = map->m_lblk + map->m_len;
+	if (eof_block < map->m_lblk + map_len)
+		eof_block = map->m_lblk + map_len;
 
 	depth = ext_depth(inode);
 	eh = path[depth].p_hdr;
 	ex = path[depth].p_ext;
 	ee_block = le32_to_cpu(ex->ee_block);
 	ee_len = ext4_ext_get_actual_len(ex);
-	allocated = ee_len - (map->m_lblk - ee_block);
 	zero_ex.ee_len = 0;
 
 	trace_ext4_ext_convert_to_initialized_enter(inode, map, ex);
@@ -3186,77 +3185,121 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 
 	/*
 	 * Attempt to transfer newly initialized blocks from the currently
-	 * uninitialized extent to its left neighbor. This is much cheaper
+	 * uninitialized extent to its neighbor. This is much cheaper
 	 * than an insertion followed by a merge as those involve costly
-	 * memmove() calls. This is the common case in steady state for
-	 * workloads doing fallocate(FALLOC_FL_KEEP_SIZE) followed by append
-	 * writes.
+	 * memmove() calls. Transferring to the left is the common case in
+	 * steady state for workloads doing fallocate(FALLOC_FL_KEEP_SIZE)
+	 * followed by append writes.
 	 *
 	 * Limitations of the current logic:
-	 *  - L1: we only deal with writes at the start of the extent.
-	 *    The approach could be extended to writes at the end
-	 *    of the extent but this scenario was deemed less common.
-	 *  - L2: we do not deal with writes covering the whole extent.
+	 *  - L1: we do not deal with writes covering the whole extent.
 	 *    This would require removing the extent if the transfer
 	 *    is possible.
-	 *  - L3: we only attempt to merge with an extent stored in the
+	 *  - L2: we only attempt to merge with an extent stored in the
 	 *    same extent tree node.
 	 */
-	if ((map->m_lblk == ee_block) &&	/*L1*/
-		(map->m_len < ee_len) &&	/*L2*/
-		(ex > EXT_FIRST_EXTENT(eh))) {	/*L3*/
-		struct ext4_extent *prev_ex;
+	if ((map->m_lblk == ee_block) &&
+		/* See if we can merge left */
+		(map_len < ee_len) &&		/*L1*/
+		(ex > EXT_FIRST_EXTENT(eh))) {	/*L2*/
 		ext4_lblk_t prev_lblk;
 		ext4_fsblk_t prev_pblk, ee_pblk;
-		unsigned int prev_len, write_len;
+		unsigned int prev_len;
 
-		prev_ex = ex - 1;
-		prev_lblk = le32_to_cpu(prev_ex->ee_block);
-		prev_len = ext4_ext_get_actual_len(prev_ex);
-		prev_pblk = ext4_ext_pblock(prev_ex);
+		abut_ex = ex - 1;
+		prev_lblk = le32_to_cpu(abut_ex->ee_block);
+		prev_len = ext4_ext_get_actual_len(abut_ex);
+		prev_pblk = ext4_ext_pblock(abut_ex);
 		ee_pblk = ext4_ext_pblock(ex);
-		write_len = map->m_len;
 
 		/*
-		 * A transfer of blocks from 'ex' to 'prev_ex' is allowed
+		 * A transfer of blocks from 'ex' to 'abut_ex' is allowed
 		 * upon those conditions:
-		 * - C1: prev_ex is initialized,
-		 * - C2: prev_ex is logically abutting ex,
-		 * - C3: prev_ex is physically abutting ex,
-		 * - C4: prev_ex can receive the additional blocks without
+		 * - C1: abut_ex is initialized,
+		 * - C2: abut_ex is logically abutting ex,
+		 * - C3: abut_ex is physically abutting ex,
+		 * - C4: abut_ex can receive the additional blocks without
 		 *   overflowing the (initialized) length limit.
 		 */
-		if ((!ext4_ext_is_uninitialized(prev_ex)) &&		/*C1*/
+		if ((!ext4_ext_is_uninitialized(abut_ex)) &&		/*C1*/
 			((prev_lblk + prev_len) == ee_block) &&		/*C2*/
 			((prev_pblk + prev_len) == ee_pblk) &&		/*C3*/
-			(prev_len < (EXT_INIT_MAX_LEN - write_len))) {	/*C4*/
+			(prev_len < (EXT_INIT_MAX_LEN - map_len))) {	/*C4*/
 			err = ext4_ext_get_access(handle, inode, path + depth);
 			if (err)
 				goto out;
 
 			trace_ext4_ext_convert_to_initialized_fastpath(inode,
-				map, ex, prev_ex);
+				map, ex, abut_ex);
 
-			/* Shift the start of ex by 'write_len' blocks */
-			ex->ee_block = cpu_to_le32(ee_block + write_len);
-			ext4_ext_store_pblock(ex, ee_pblk + write_len);
-			ex->ee_len = cpu_to_le16(ee_len - write_len);
+			/* Shift the start of ex by 'map_len' blocks */
+			ex->ee_block = cpu_to_le32(ee_block + map_len);
+			ext4_ext_store_pblock(ex, ee_pblk + map_len);
+			ex->ee_len = cpu_to_le16(ee_len - map_len);
 			ext4_ext_mark_uninitialized(ex); /* Restore the flag */
 
-			/* Extend prev_ex by 'write_len' blocks */
-			prev_ex->ee_len = cpu_to_le16(prev_len + write_len);
+			/* Extend abut_ex by 'map_len' blocks */
+			abut_ex->ee_len = cpu_to_le16(prev_len + map_len);
 
-			/* Mark the block containing both extents as dirty */
-			ext4_ext_dirty(handle, inode, path + depth);
+			/* Result: number of initialized blocks past m_lblk */
+			allocated = map_len;
+		}
+	} else if (((map->m_lblk + map_len) == (ee_block + ee_len)) &&
+		   (map_len < ee_len) &&	/*L1*/
+		   ex < EXT_LAST_EXTENT(eh)) {	/*L2*/
+		/* See if we can merge right */
+		ext4_lblk_t next_lblk;
+		ext4_fsblk_t next_pblk, ee_pblk;
+		unsigned int next_len;
+
+		abut_ex = ex + 1;
+		next_lblk = le32_to_cpu(abut_ex->ee_block);
+		next_len = ext4_ext_get_actual_len(abut_ex);
+		next_pblk = ext4_ext_pblock(abut_ex);
+		ee_pblk = ext4_ext_pblock(ex);
 
-			/* Update path to point to the right extent */
-			path[depth].p_ext = prev_ex;
+		/*
+		 * A transfer of blocks from 'ex' to 'abut_ex' is allowed
+		 * upon those conditions:
+		 * - C1: abut_ex is initialized,
+		 * - C2: abut_ex is logically abutting ex,
+		 * - C3: abut_ex is physically abutting ex,
+		 * - C4: abut_ex can receive the additional blocks without
+		 *   overflowing the (initialized) length limit.
+		 */
+		if ((!ext4_ext_is_uninitialized(abut_ex)) &&		/*C1*/
+		    ((map->m_lblk + map_len) == next_lblk) &&		/*C2*/
+		    ((ee_pblk + ee_len) == next_pblk) &&		/*C3*/
+		    (next_len < (EXT_INIT_MAX_LEN - map_len))) {	/*C4*/
+			err = ext4_ext_get_access(handle, inode, path + depth);
+			if (err)
+				goto out;
+
+			trace_ext4_ext_convert_to_initialized_fastpath(inode,
+				map, ex, abut_ex);
+
+			/* Shift the start of abut_ex by 'map_len' blocks */
+			abut_ex->ee_block = cpu_to_le32(next_lblk - map_len);
+			ext4_ext_store_pblock(abut_ex, next_pblk - map_len);
+			ex->ee_len = cpu_to_le16(ee_len - map_len);
+			ext4_ext_mark_uninitialized(ex); /* Restore the flag */
+
+			/* Extend abut_ex by 'map_len' blocks */
+			abut_ex->ee_len = cpu_to_le16(next_len + map_len);
 
 			/* Result: number of initialized blocks past m_lblk */
-			allocated = write_len;
-			goto out;
+			allocated = map_len;
 		}
 	}
+	if (allocated) {
+		/* Mark the block containing both extents as dirty */
+		ext4_ext_dirty(handle, inode, path + depth);
+
+		/* Update path to point to the right extent */
+		path[depth].p_ext = abut_ex;
+		goto out;
+	} else
+		allocated = ee_len - (map->m_lblk - ee_block);
 
 	WARN_ON(map->m_lblk < ee_block);
 	/*