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Commit e8340395 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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ext4: protect extent conversion after DIO with i_dio_count 



Make sure extent conversion after DIO happens while i_dio_count is
still elevated so that inode_dio_wait() waits until extent conversion
is done.  This removes the need for explicit waiting for extent
conversion in some cases.

Reviewed-by: default avatarZheng Liu <wenqing.lz@taobao.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent b0857d30

fs/ext4/inode.c

+10 −2
Original line number Diff line number Diff line
@@ -3036,11 +3036,18 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, 


	BUG_ON(iocb->private == NULL);



	/*

	 * Make all waiters for direct IO properly wait also for extent

	 * conversion. This also disallows race between truncate() and

	 * overwrite DIO as i_dio_count needs to be incremented under i_mutex.

	 */

	if (rw == WRITE)

		atomic_inc(&inode->i_dio_count);



	/* If we do a overwrite dio, i_mutex locking can be released */

	overwrite = *((int *)iocb->private);



	if (overwrite) {

		atomic_inc(&inode->i_dio_count);

		down_read(&EXT4_I(inode)->i_data_sem);

		mutex_unlock(&inode->i_mutex);

	}
@@ -3143,9 +3150,10 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, 
	}



retake_lock:

	if (rw == WRITE)

		inode_dio_done(inode);

	/* take i_mutex locking again if we do a ovewrite dio */

	if (overwrite) {

		inode_dio_done(inode);

		up_read(&EXT4_I(inode)->i_data_sem);

		mutex_lock(&inode->i_mutex);

	}