ext4: fix incorect journal credits reservation in ext4_zero_range

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@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index b9a7bd3d561ed7959de7dadfe5a4eb339338a7e1..6f9491affb269c573b58b19262cef3c956888425 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4730,6 +4730,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
        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 *file, loff_t offset,
                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);