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