From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 4 Oct 2016 00:38:55 +0000 (-0400)
Subject: consistent treatment of EFAULT on O_DIRECT read/write
X-Git-Tag: v4.9-rc1~85^2~15
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4038acdb187e226e72df393ae3dd150df857e8a3;p=thirdparty%2Fkernel%2Flinux.git

consistent treatment of EFAULT on O_DIRECT read/write

Make local filesystems treat a fault as shortened IO,
returning -EFAULT only if nothing had been transferred.
That's how everything else (NFS, FUSE, ceph, Lustre)
behaves.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 7c3ce73cb6170..fb9aa16a77272 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -246,6 +246,9 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
 		if ((dio->op == REQ_OP_READ) &&
 		    ((offset + transferred) > dio->i_size))
 			transferred = dio->i_size - offset;
+		/* ignore EFAULT if some IO has been done */
+		if (unlikely(ret == -EFAULT) && transferred)
+			ret = 0;
 	}
 
 	if (ret == 0)