linux-kernel - [PATCH v2 2/6] iomap: Fix iomap_dio

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Message-Id: <20210718223932.2703330-3-agruenba@redhat.com>
Date:   Mon, 19 Jul 2021 00:39:28 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Christoph Hellwig <hch@...radead.org>,
        cluster-devel@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, ocfs2-devel@....oracle.com,
        Andreas Gruenbacher <agruenba@...hat.com>
Subject: [PATCH v2 2/6] iomap: Fix iomap_dio_rw return value for page faults

When a page fault occurs during a direct I/O, iomap_dio_rw can currently return
0 when a page cannot be accessed.  In that case, -EFAULT should be returned
instead.  (For reads, a return value of 0 indicates the end of file.)  Fix that
by casting the return value of iomap_apply from 0 to -EFAULT: in that position,
we know that we should have been able to read something.

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
 fs/iomap/direct-io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 9398b8c31323..a87a43ee8278 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -561,6 +561,8 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 		ret = iomap_apply(inode, pos, count, iomap_flags, ops, dio,
 				iomap_dio_actor);
 		if (ret <= 0) {
+			if (ret == 0)
+				ret = -EFAULT;
 			/* magic error code to fall back to buffered I/O */
 			if (ret == -ENOTBLK) {
 				wait_for_completion = true;
-- 
2.26.3