linux-kernel - [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE

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Message-ID: <545463.1686601473@warthog.procyon.org.uk>
Date:   Mon, 12 Jun 2023 21:24:33 +0100
From:   David Howells <dhowells@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>, David Hildenbrand <david@...hat.com>,
        kernel test robot <oliver.sang@...el.com>
cc:     dhowells@...hat.com, Christoph Hellwig <hch@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Hillf Danton <hdanton@...a.com>,
        Christian Brauner <brauner@...nel.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-mm@...ck.org, oe-lkp@...ts.linux.dev, lkp@...el.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

    
Fix dio_bio_alloc() to set BIO_PAGE_PINNED, not BIO_PAGE_REFFED, so that
the bio code unpins the pinned pages rather than putting a ref on them.

The issue was causing:

        WARNING: CPU: 6 PID: 2220 at mm/gup.c:76 try_get_folio

This can be caused by creating a file on a loopback UDF filesystem, opening
it O_DIRECT and making two writes to it from the same source buffer.

Fixes: 1ccf164ec866 ("block: Use iov_iter_extract_pages() and page pinning in direct-io.c")
Reported-by: kernel test robot <oliver.sang@...el.com>
Closes: https://lore.kernel.org/oe-lkp/202306120931.a9606b88-oliver.sang@intel.com
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Christoph Hellwig <hch@...radead.org>
cc: David Hildenbrand <david@...hat.com>
cc: Andrew Morton <akpm@...ux-foundation.org>
cc: Jens Axboe <axboe@...nel.dk>
cc: Al Viro <viro@...iv.linux.org.uk>
cc: Matthew Wilcox <willy@...radead.org>
cc: Jan Kara <jack@...e.cz>
cc: Jeff Layton <jlayton@...nel.org>
cc: Jason Gunthorpe <jgg@...dia.com>
cc: Logan Gunthorpe <logang@...tatee.com>
cc: Hillf Danton <hdanton@...a.com>
cc: Christian Brauner <brauner@...nel.org>
cc: Linus Torvalds <torvalds@...ux-foundation.org>
cc: linux-fsdevel@...r.kernel.org
cc: linux-block@...r.kernel.org
cc: linux-kernel@...r.kernel.org
cc: linux-mm@...ck.org
---

Notes:
    ver #2)
     - Remove comment on requiring references for all pages.

 fs/direct-io.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 14049204cac8..5d4c5be0fb41 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -414,8 +414,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
 		bio->bi_end_io = dio_bio_end_aio;
 	else
 		bio->bi_end_io = dio_bio_end_io;
-	/* for now require references for all pages */
-	bio_set_flag(bio, BIO_PAGE_REFFED);
+	if (dio->need_unpin)
+		bio_set_flag(bio, BIO_PAGE_PINNED);
 	sdio->bio = bio;
 	sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
 }