On Mon, Feb 17, 2020 at 08:23:59PM +0800, Zhihao Cheng wrote:
> [ Upstream commit f5de5b83303e61b1f3fb09bd77ce3ac2d7a475f2 ]
>
> In ubifs, concurrent execution of writepage and bulk read on the same file
> may cause ABBA deadlock, for example (Reproduce method see Link):
>
> Process A(Bulk-read starts from page4) Process B(write page4 back)
> vfs_read wb_workfn or fsync
> ... ...
> generic_file_buffered_read write_cache_pages
> ubifs_readpage LOCK(page4)
>
> ubifs_bulk_read ubifs_writepage
> LOCK(ui->ui_mutex) ubifs_write_inode
>
> ubifs_do_bulk_read LOCK(ui->ui_mutex)
> find_or_create_page(alloc page4) ↑
> LOCK(page4) <-- ABBA deadlock occurs!
>
> In order to ensure the serialization execution of bulk read, we can't
> remove the big lock 'ui->ui_mutex' in ubifs_bulk_read(). Instead, we
> allow ubifs_do_bulk_read() to lock page failed by replacing
> find_or_create_page(FGP_LOCK) with
> pagecache_get_page(FGP_LOCK | FGP_NOWAIT).
>
> Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
> Suggested-by: zhangyi (F) <yi.zhang@xxxxxxxxxx>
> Cc: <Stable@xxxxxxxxxxxxxxx>
> Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206153
> Signed-off-by: Richard Weinberger <richard@xxxxxx>
> ---
> fs/ubifs/file.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> index b895af7d8d80..e6d0a7df341d 100644
> --- a/fs/ubifs/file.c
> +++ b/fs/ubifs/file.c
> @@ -782,8 +782,9 @@ static int ubifs_do_bulk_read(struct ubifs_info *c, struct bu_info *bu,
>
> if (page_offset > end_index)
> break;
> - page = find_or_create_page(mapping, page_offset,
> - GFP_NOFS | __GFP_COLD);
> + page = pagecache_get_page(mapping, page_offset,
> + FGP_LOCK|FGP_ACCESSED|FGP_CREAT|FGP_NOWAIT,
> + GFP_NOFS | __GFP_COLD);
> if (!page)
> break;
> if (!PageUptodate(page))
> --
> 2.7.4
>
Now applied, thanks!
greg k-h
