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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: 16c5468859 ("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>
This commit is contained in:
Eric Biggers 2017-05-24 18:05:29 -04:00 committed by Theodore Ts'o
parent 624327f879
commit e5465795ca
1 changed files with 1 additions and 1 deletions
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2
fs/ext4/inode.c
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@ -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,