| Message ID | 1578736236-141308-1-git-send-email-chengzhihao1@huawei.com |
|---|---|
| State | Accepted |
| Delegated to: | Richard Weinberger |
| Headers | show |
| Series | [v2] ubifs: Fix deadlock in concurrent bulk-read and writepage | expand |
On Sat, Jan 11, 2020 at 10:43 AM Zhihao Cheng <chengzhihao1@huawei.com> wrote: > > 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 > --- > fs/ubifs/file.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) Applied. Thanks a lot for hunting this down!
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c index cd52585..c649048 100644 --- a/fs/ubifs/file.c +++ b/fs/ubifs/file.c @@ -786,7 +786,9 @@ 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, ra_gfp_mask); + page = pagecache_get_page(mapping, page_offset, + FGP_LOCK|FGP_ACCESSED|FGP_CREAT|FGP_NOWAIT, + ra_gfp_mask); if (!page) break; if (!PageUptodate(page))
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 --- fs/ubifs/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)