[PATCH] block: Fix dio_cleanup() to advance the head index

[David Howells]

Fix dio_bio_cleanup() to advance the head index into the list of pages past
the pages it has released, as __blockdev_direct_IO() will call it twice if
do_direct_IO() fails.

The issue was causing:

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

This can be triggered by setting up a clean pair of UDF filesystems on
loopback devices and running the generic/451 xfstest with them as the
scratch and test partitions.  Something like the following:

    fallocate /mnt2/udf_scratch -l 1G
    fallocate /mnt2/udf_test -l 1G
    mknod /dev/lo0 b 7 0
    mknod /dev/lo1 b 7 1
    losetup lo0 /mnt2/udf_scratch
    losetup lo1 /mnt2/udf_test
    mkfs -t udf /dev/lo0
    mkfs -t udf /dev/lo1
    cd xfstests
    ./check generic/451

with xfstests configured by putting the following into local.config:

    export FSTYP=udf
    export DISABLE_UDF_TEST=1
    export TEST_DEV=/dev/lo1
    export TEST_DIR=/xfstest.test
    export SCRATCH_DEV=/dev/lo0
    export SCRATCH_MNT=/xfstest.scratch

Fixes: 1ccf164ec866 ("block: Use iov_iter_extract_pages() and page pinning in direct-io.c")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202306120931.a9606b88-oliver.sang@xxxxxxxxx
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
cc: David Hildenbrand <david@xxxxxxxxxx>
cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: Jan Kara <jack@xxxxxxx>
cc: Jeff Layton <jlayton@xxxxxxxxxx>
cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
cc: Hillf Danton <hdanton@xxxxxxxx>
cc: Christian Brauner <brauner@xxxxxxxxxx>
cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
cc: linux-fsdevel@xxxxxxxxxxxxxxx
cc: linux-block@xxxxxxxxxxxxxxx
cc: linux-kernel@xxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
---
 fs/direct-io.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 0643f1bb4b59..2ceb378b93c0 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -459,6 +459,7 @@ static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
 	if (dio->is_pinned)
 		unpin_user_pages(dio->pages + sdio->head,
 				 sdio->tail - sdio->head);
+	sdio->head = sdio->tail;
 }
 
 /*