2023-06-12 17:16:55

by David Howells

Subject: [PATCH] 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 <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Signed-off-by: David Howells <[email protected]>
cc: Christoph Hellwig <[email protected]>
cc: David Hildenbrand <[email protected]>
cc: Andrew Morton <[email protected]>
cc: Jens Axboe <[email protected]>
cc: Al Viro <[email protected]>
cc: Matthew Wilcox <[email protected]>
cc: Jan Kara <[email protected]>
cc: Jeff Layton <[email protected]>
cc: Jason Gunthorpe <[email protected]>
cc: Logan Gunthorpe <[email protected]>
cc: Hillf Danton <[email protected]>
cc: Christian Brauner <[email protected]>
cc: Linus Torvalds <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
---
fs/direct-io.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 14049204cac8..04e810826ee8 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -415,7 +415,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
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;
}

2023-06-12 18:27:20

by David Hildenbrand

Subject: Re: [PATCH] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

On 12.06.23 18:51, David Howells wrote:
>
> 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 <[email protected]>
> Closes: https://lore.kernel.org/oe-lkp/[email protected]
> Signed-off-by: David Howells <[email protected]>
> cc: Christoph Hellwig <[email protected]>
> cc: David Hildenbrand <[email protected]>
> cc: Andrew Morton <[email protected]>
> cc: Jens Axboe <[email protected]>
> cc: Al Viro <[email protected]>
> cc: Matthew Wilcox <[email protected]>
> cc: Jan Kara <[email protected]>
> cc: Jeff Layton <[email protected]>
> cc: Jason Gunthorpe <[email protected]>
> cc: Logan Gunthorpe <[email protected]>
> cc: Hillf Danton <[email protected]>
> cc: Christian Brauner <[email protected]>
> cc: Linus Torvalds <[email protected]>
> cc: [email protected]
> cc: [email protected]
> cc: [email protected]
> cc: [email protected]
> ---
> fs/direct-io.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 14049204cac8..04e810826ee8 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -415,7 +415,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
> else
> bio->bi_end_io = dio_bio_end_io;
> /* for now require references for all pages */

Does the comment still hold?

> - 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;
> }
>

--
Cheers,

David / dhildenb

2023-06-12 19:17:32

by David Howells

Subject: Re: [PATCH] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

David Hildenbrand <[email protected]> wrote:

> > /* for now require references for all pages */
>
> Does the comment still hold?

Actually, no.

David

2023-06-13 21:39:53

by David Howells

Subject: Re: [PATCH] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

Okay, it isn't this. The problem appears to be that __blockdev_direct_IO()
calls dio_cleanup() twice if do_direct_IO() fails.

David

2023-06-13 21:57:40

by David Howells

Subject: Re: [PATCH] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
{
- while (sdio->head < sdio->tail)
- put_page(dio->pages[sdio->head++]);
+ if (dio->is_pinned)
+ unpin_user_pages(dio->pages + sdio->head,
+ sdio->tail - sdio->head);
}

/*

Meh. It's obvious. Need to advance head.

David