[1/1] ext4: Fix ext4_mb_normalize_request

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 4da228a..0af9aaf 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4412,12 +4412,28 @@  int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 	 * EXT_INIT_MAX_LEN and for an unwritten extent this limit is
 	 * EXT_UNWRITTEN_MAX_LEN.
 	 */
+	ar.flags = 0;
 	if (map->m_len > EXT_INIT_MAX_LEN &&
-	    !(flags & EXT4_GET_BLOCKS_UNWRIT_EXT))
+	    !(flags & EXT4_GET_BLOCKS_UNWRIT_EXT)) {
 		map->m_len = EXT_INIT_MAX_LEN;
-	else if (map->m_len > EXT_UNWRITTEN_MAX_LEN &&
-		 (flags & EXT4_GET_BLOCKS_UNWRIT_EXT))
-		map->m_len = EXT_UNWRITTEN_MAX_LEN;
+		/*
+		 * We're going to allocate as much as we can
+		 * so there is no reason to do preallocation
+		 */
+		ar.flags |= EXT4_MB_HINT_NOPREALLOC;
+	} else if (map->m_len >= EXT_UNWRITTEN_MAX_LEN &&
+		 (flags & EXT4_GET_BLOCKS_UNWRIT_EXT)) {
+		/*
+		 * We want to avoid unnecessary fragmentation. Setting this
+		 * to EXT_UNWRITTEN_MAX_LEN would leave 1 block in the block
+		 * group.
+		 */
+		map->m_len = EXT_INIT_MAX_LEN / 2;
+	}
+
+	/* Disable preallocation for unwritten extents. */
+	if (flags & EXT4_GET_BLOCKS_UNWRIT_EXT)
+		ar.flags |= EXT4_MB_HINT_NOPREALLOC;
 
 	/* Check if we can really insert (m_lblk)::(m_lblk + m_len) extent */
 	newex.ee_len = cpu_to_le16(map->m_len);
@@ -4444,10 +4460,7 @@  int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 	ar.goal -= offset;
 	ar.logical -= offset;
 	if (S_ISREG(inode->i_mode))
-		ar.flags = EXT4_MB_HINT_DATA;
-	else
-		/* disable in-core preallocation for non-regular files */
-		ar.flags = 0;
+		ar.flags |= EXT4_MB_HINT_DATA;
 	if (flags & EXT4_GET_BLOCKS_NO_NORMALIZE)
 		ar.flags |= EXT4_MB_HINT_NOPREALLOC;
 	newblock = ext4_mb_new_blocks(handle, &ar, &err);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 59e3162..cc55150 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2993,10 +2993,9 @@  ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 				struct ext4_allocation_request *ar)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
-	int bsbits, max;
-	ext4_lblk_t end;
-	loff_t size, start_off;
-	loff_t orig_size __maybe_unused;
+	int bsbits;
+	loff_t end;
+	loff_t size;
 	ext4_lblk_t start;
 	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
 	struct ext4_prealloc_space *pa;
@@ -3022,64 +3021,29 @@  ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 
 	bsbits = ac->ac_sb->s_blocksize_bits;
 
-	/* first, let's learn actual file size
-	 * given current request is allocated */
-	size = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
-	size = size << bsbits;
-	if (size < i_size_read(ac->ac_inode))
-		size = i_size_read(ac->ac_inode);
-	orig_size = size;
-
-	/* max size of free chunks */
-	max = 2 << bsbits;
-
-#define NRL_CHECK_SIZE(req, size, max, chunk_size)	\
-		(req <= (size) || max <= (chunk_size))
-
-	/* first, try to predict filesize */
-	/* XXX: should this table be tunable? */
-	start_off = 0;
-	if (size <= 16 * 1024) {
-		size = 16 * 1024;
-	} else if (size <= 32 * 1024) {
-		size = 32 * 1024;
-	} else if (size <= 64 * 1024) {
-		size = 64 * 1024;
-	} else if (size <= 128 * 1024) {
-		size = 128 * 1024;
-	} else if (size <= 256 * 1024) {
-		size = 256 * 1024;
-	} else if (size <= 512 * 1024) {
-		size = 512 * 1024;
-	} else if (size <= 1024 * 1024) {
-		size = 1024 * 1024;
-	} else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, 2 * 1024)) {
-		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
-						(21 - bsbits)) << 21;
-		size = 2 * 1024 * 1024;
-	} else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, 4 * 1024)) {
-		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
-							(22 - bsbits)) << 22;
-		size = 4 * 1024 * 1024;
-	} else if (NRL_CHECK_SIZE(ac->ac_o_ex.fe_len,
-					(8<<20)>>bsbits, max, 8 * 1024)) {
-		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
-							(23 - bsbits)) << 23;
-		size = 8 * 1024 * 1024;
-	} else {
-		start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits;
-		size	  = ac->ac_o_ex.fe_len << bsbits;
-	}
-	size = size >> bsbits;
-	start = start_off >> bsbits;
+	end = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
+	if ((end << bsbits) < i_size_read(ac->ac_inode))
+		end = i_size_read(ac->ac_inode) >> bsbits;
+
+	/* Guess the file size -- round up to nearest power of two */
+	end = roundup_pow_of_two(end + 1);
+	start = ac->ac_o_ex.fe_logical;
+
+	/* Get the actual allocation size */
+	size = end - start;
+
+	/* We can not allocate more blocks than can be found in the group */
+	if (size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb))
+		size = EXT4_BLOCKS_PER_GROUP(ac->ac_sb);
 
 	/* don't cover already allocated blocks in selected range */
 	if (ar->pleft && start <= ar->lleft) {
 		size -= ar->lleft + 1 - start;
 		start = ar->lleft + 1;
 	}
-	if (ar->pright && start + size - 1 >= ar->lright)
-		size -= start + size - ar->lright;
+	end = start + size;
+	if (ar->pright && end - 1 >= ar->lright)
+		size -= (end - ar->lright);
 
 	end = start + size;
 
@@ -3173,7 +3137,7 @@  ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 	}
 
 	mb_debug(1, "goal: %u(was %u) blocks at %u\n", (unsigned) size,
-		(unsigned) orig_size, (unsigned) start);
+		(unsigned) ac->ac_o_ex.fe_logical, (unsigned) start);
 }
 
 static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)