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Commit ff5462e3 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Theodore Ts'o
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ext4: fix DAX write locking 



Unlike O_DIRECT DAX is not an optional opt-in feature selected by the
application, so we'll have to provide the traditional synchronіzation
of overlapping writes as we do for buffered writes.

This was broken historically for DAX, but got fixed for ext2 and XFS
as part of the iomap conversion.  Fix up ext4 as well.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
parent 783d9485

fs/ext4/file.c

+1 −9
Original line number Diff line number Diff line
@@ -178,7 +178,6 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from) 
{

	struct inode *inode = file_inode(iocb->ki_filp);

	ssize_t ret;

	bool overwrite = false;



	inode_lock(inode);

	ret = ext4_write_checks(iocb, from);
@@ -191,16 +190,9 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from) 
	if (ret)

		goto out;



	if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {

		overwrite = true;

		downgrade_write(&inode->i_rwsem);

	}

	ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);

out:

	if (!overwrite)

	inode_unlock(inode);

	else

		inode_unlock_shared(inode);

	if (ret > 0)

		ret = generic_write_sync(iocb, ret);

	return ret;