[PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[David Howells]

    
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@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202306120931.a9606b88-oliver.sang@intel.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@infradead.org>
cc: David Hildenbrand <david@redhat.com>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Matthew Wilcox <willy@infradead.org>
cc: Jan Kara <jack@suse.cz>
cc: Jeff Layton <jlayton@kernel.org>
cc: Jason Gunthorpe <jgg@nvidia.com>
cc: Logan Gunthorpe <logang@deltatee.com>
cc: Hillf Danton <hdanton@sina.com>
cc: Christian Brauner <brauner@kernel.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-kernel@vger.kernel.org
cc: linux-mm@kvack.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;
 }

Re: [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[David Hildenbrand]

On 12.06.23 22:24, 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 <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202306120931.a9606b88-oliver.sang@intel.com
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Christoph Hellwig <hch@infradead.org>
> cc: David Hildenbrand <david@redhat.com>
> cc: Andrew Morton <akpm@linux-foundation.org>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Al Viro <viro@zeniv.linux.org.uk>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: Jan Kara <jack@suse.cz>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: Jason Gunthorpe <jgg@nvidia.com>
> cc: Logan Gunthorpe <logang@deltatee.com>
> cc: Hillf Danton <hdanton@sina.com>
> cc: Christian Brauner <brauner@kernel.org>
> cc: Linus Torvalds <torvalds@linux-foundation.org>
> cc: linux-fsdevel@vger.kernel.org
> cc: linux-block@vger.kernel.org
> cc: linux-kernel@vger.kernel.org
> cc: linux-mm@kvack.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;
>   }
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[Jens Axboe]

On 6/12/23 2:24 PM, 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.

What is this against?

-- 
Jens Axboe

Re: [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[David Howells]

Jens Axboe <axboe@kernel.dk> wrote:

> What is this against?

It's against the branch I posted.  I should rebase it on your tree, but I'm in
a conference at the moment, so that may have to wait till Thursday.

David

Re: [PATCH v2] block: Fix dio_bio_alloc() to set BIO_PAGE_PINNED

[David Howells]

David Howells <dhowells@redhat.com> wrote:

> > What is this against?
> 
> It's against the branch I posted.

Actually, it's not.  It's against an old version of the patch on a different
branch.  The patches you have applied already have that change - so the issue
must be something else:-/

David