From fe683adabfe6629c0b6db32bbbc1ce6cacbf2117 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 15 Jan 2016 16:55:56 -0800
Subject: dax: guarantee page aligned results from bdev_direct_access()

If a ->direct_access() implementation ever returns a map count less than
PAGE_SIZE, catch the error in bdev_direct_access().  This simplifies
error checking in upper layers.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 fs/block_dev.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'fs/block_dev.c')

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 81c0705558be..ddc6cdd1860b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -494,6 +494,8 @@ long bdev_direct_access(struct block_device *bdev, sector_t sector,
 	avail = ops->direct_access(bdev, sector, addr, pfn);
 	if (!avail)
 		return -ERANGE;
+	if (avail > 0 && avail & ~PAGE_MASK)
+		return -ENXIO;
 	return min(avail, size);
 }
 EXPORT_SYMBOL_GPL(bdev_direct_access);
-- 
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