Commit 53bb540f authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Explain some direct I/O oddities 



Add some comments explaining the oddities of partial direct I/O reads
and writes.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent b846f2d7

fs/gfs2/file.c

+4 −0
Original line number Diff line number Diff line
@@ -840,6 +840,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to, 
	pagefault_enable();

	if (ret <= 0 && ret != -EFAULT)

		goto out_unlock;

	/* No increment (+=) because iomap_dio_rw returns a cumulative value. */

	if (ret > 0)

		read = ret;
@@ -854,6 +855,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to, 
		gfs2_glock_dq(gh);

out_uninit:

	gfs2_holder_uninit(gh);

	/* User space doesn't expect partial success. */

	if (ret < 0)

		return ret;

	return read;
@@ -906,6 +908,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from, 
		if (ret != -EFAULT)

			goto out_unlock;

	}

	/* No increment (+=) because iomap_dio_rw returns a cumulative value. */

	if (ret > 0)

		written = ret;
@@ -920,6 +923,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from, 
		gfs2_glock_dq(gh);

out_uninit:

	gfs2_holder_uninit(gh);

	/* User space doesn't expect partial success. */

	if (ret < 0)

		return ret;

	return written;