From: Jeff Moyer <jmoyer@redhat.com>
Date: Fri, 14 Aug 2015 20:15:31 +0000 (-0400)
Subject: dax: fix O_DIRECT I/O to the last block of a blockdev
X-Git-Tag: v4.2.4~210
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fda7e543449bf0fde30464e8005dba8f1af36a2d;p=thirdparty%2Fkernel%2Fstable.git

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

commit e94f5a2285fc94202a9efb2c687481f29b64132c upstream.

commit bbab37ddc20b (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.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/dax.c b/fs/dax.c
index a7f77e1fa18c2..ef35a20145807 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -116,7 +116,8 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 		unsigned 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;