Commit e94f5a22 authored Aug 14, 2015 by Jeff Moyer Committed by Dan Williams Sep 15, 2015

dax: fix O_DIRECT I/O to the last block of a blockdev



commit bbab37dd (block: Add support for DAX reads/writes to
block devices) caused a regression in mkfs.xfs.  That utility
sets the block size of the device to the logical block size
using the BLKBSZSET ioctl, and then issues a single sector read
from the last sector of the device.  This results in the dax_io
code trying to do a page-sized read from 512 bytes from the end
of the device.  The result is -ERANGE being returned to userspace.

The fix is to align the block to the page size before calling
get_block.

Thanks to willy for simplifying my original patch.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Tested-by: Linda Knippers <linda.knippers@hp.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

parent 6ff33f39

fs/dax.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -119,7 +119,8 @@ static ssize_t dax_io(struct inode inode, struct iov_iter iter,
		size_t len;
		if (pos == max) {
		unsigned blkbits = inode->i_blkbits;
		sector_t block = pos >> blkbits;
		long page = pos >> PAGE_SHIFT;
		sector_t block = page << (PAGE_SHIFT - blkbits);
		unsigned first = pos - (block << blkbits);
		long size;