* [PATCH 4.4] ubifs: Fix deadlock in concurrent bulk-read and writepage
@ 2020-02-17 12:23 Zhihao Cheng
2020-02-17 14:13 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: Zhihao Cheng @ 2020-02-17 12:23 UTC (permalink / raw)
To: richard, gregkh, sashal, yi.zhang; +Cc: linux-mtd, linux-kernel, Stable
[ 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@huawei.com>
Suggested-by: zhangyi (F) <yi.zhang@huawei.com>
Cc: <Stable@vger.kernel.org>
Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206153
Signed-off-by: Richard Weinberger <richard@nod.at>
---
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 4.4] ubifs: Fix deadlock in concurrent bulk-read and writepage
2020-02-17 12:23 [PATCH 4.4] ubifs: Fix deadlock in concurrent bulk-read and writepage Zhihao Cheng
@ 2020-02-17 14:13 ` Greg KH
0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2020-02-17 14:13 UTC (permalink / raw)
To: Zhihao Cheng; +Cc: richard, sashal, yi.zhang, linux-mtd, linux-kernel, Stable
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@huawei.com>
> Suggested-by: zhangyi (F) <yi.zhang@huawei.com>
> Cc: <Stable@vger.kernel.org>
> Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206153
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
> 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
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