ext4: fix DAX write locking (ff5462e3) · Commits · 戴 / test

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:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Reviewed-by:

Jan Kara <jack@suse.cz>

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;

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