From: Eric Biggers <ebiggers@google.com>
Date: Wed, 24 May 2017 22:05:29 +0000 (-0400)
Subject: ext4: fix off-by-one error when writing back pages before dio read
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=e5465795cac48233c9b606a7a419f4190a91851e;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

ext4: fix off-by-one error when writing back pages before dio read

The 'lend' argument of filemap_write_and_wait_range() is inclusive, so
we need to subtract 1 from pos + count.

Note that 'count' is guaranteed to be nonzero since
ext4_file_read_iter() returns early when given a 0 count.

Fixes: 16c54688592c ("ext4: Allow parallel DIO reads")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
---

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7cd99de8c4ba..90b264928742 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3713,7 +3713,7 @@ static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
 	 */
 	inode_lock_shared(inode);
 	ret = filemap_write_and_wait_range(mapping, iocb->ki_pos,
-					   iocb->ki_pos + count);
+					   iocb->ki_pos + count - 1);
 	if (ret)
 		goto out_unlock;
 	ret = __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev,