[PATCH 3.16 096/125] ext4: fix incorect journal credits reservation in ext4_zero_range

[Greg Kroah-Hartman]

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>

commit 69dc9536405213c1d545fcace1fc15c481d00aae upstream.

Currently we reserve only 4 blocks but in worst case scenario
ext4_zero_partial_blocks() may want to zeroout and convert two
non adjacent blocks.

Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ext4/extents.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4730,6 +4730,7 @@ static long ext4_zero_range(struct file
 	loff_t new_size = 0;
 	int ret = 0;
 	int flags;
+	int credits;
 	int partial;
 	loff_t start, end;
 	ext4_lblk_t lblk;
@@ -4829,8 +4830,14 @@ static long ext4_zero_range(struct file
 		if (ret)
 			goto out_dio;
 	}
-
-	handle = ext4_journal_start(inode, EXT4_HT_MISC, 4);
+	/*
+	 * In worst case we have to writeout two nonadjacent unwritten
+	 * blocks and update the inode
+	 */
+	credits = (2 * ext4_ext_index_trans_blocks(inode, 2)) + 1;
+	if (ext4_should_journal_data(inode))
+		credits += 2;
+	handle = ext4_journal_start(inode, EXT4_HT_MISC, credits);
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
 		ext4_std_error(inode->i_sb, ret);


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