The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From afd427048047e8efdedab30e8888044e2be5aa9c Mon Sep 17 00:00:00 2001 From: Zhihao Cheng chengzhihao1@huawei.com Date: Mon, 27 Dec 2021 11:22:33 +0800 Subject: [PATCH] ubifs: Fix deadlock in concurrent rename whiteout and inode writeback MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
Following hung tasks: [ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132 [ 77.028820] Call Trace: [ 77.029027] schedule+0x8c/0x1b0 [ 77.029067] mutex_lock+0x50/0x60 [ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs] [ 77.029117] __writeback_single_inode+0x43c/0x570 [ 77.029128] writeback_sb_inodes+0x259/0x740 [ 77.029148] wb_writeback+0x107/0x4d0 [ 77.029163] wb_workfn+0x162/0x7b0
[ 92.390442] task:aa state:D stack: 0 pid: 1506 [ 92.390448] Call Trace: [ 92.390458] schedule+0x8c/0x1b0 [ 92.390461] wb_wait_for_completion+0x82/0xd0 [ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110 [ 92.390472] writeback_inodes_sb_nr+0x14/0x20 [ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs] [ 92.390503] do_rename.cold+0x7f/0x187 [ubifs] [ 92.390549] ubifs_rename+0x8b/0x180 [ubifs] [ 92.390571] vfs_rename+0xdb2/0x1170 [ 92.390580] do_renameat2+0x554/0x770
, are caused by concurrent rename whiteout and inode writeback processes: rename_whiteout(Thread 1) wb_workfn(Thread2) ubifs_rename do_rename lock_4_inodes (Hold ui_mutex) ubifs_budget_space make_free_space shrink_liability __writeback_inodes_sb_nr bdi_split_work_to_wbs (Queue new wb work) wb_do_writeback(wb work) __writeback_single_inode ubifs_write_inode LOCK(ui_mutex) ↑ wb_wait_for_completion (Wait wb work) <-- deadlock!
Reproducer (Detail program in [Link]): 1. SYS_renameat2("/mp/dir/file", "/mp/dir/whiteout", RENAME_WHITEOUT) 2. Consume out of space before kernel(mdelay) doing budget for whiteout
Fix it by doing whiteout space budget before locking ubifs inodes. BTW, it also fixes wrong goto tag 'out_release' in whiteout budget error handling path(It should at least recover dir i_size and unlock 4 ubifs inodes).
Fixes: 9e0a1fff8db56ea ("ubifs: Implement RENAME_WHITEOUT") Link: https://bugzilla.kernel.org/show_bug.cgi?id=214733 Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Signed-off-by: Richard Weinberger richard@nod.at
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c index d3ed93d94930..f4783e1ae775 100644 --- a/fs/ubifs/dir.c +++ b/fs/ubifs/dir.c @@ -1324,6 +1324,7 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
if (flags & RENAME_WHITEOUT) { union ubifs_dev_desc *dev = NULL; + struct ubifs_budget_req wht_req;
dev = kmalloc(sizeof(union ubifs_dev_desc), GFP_NOFS); if (!dev) { @@ -1345,6 +1346,20 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry, whiteout_ui->data = dev; whiteout_ui->data_len = ubifs_encode_dev(dev, MKDEV(0, 0)); ubifs_assert(c, !whiteout_ui->dirty); + + memset(&wht_req, 0, sizeof(struct ubifs_budget_req)); + wht_req.dirtied_ino = 1; + wht_req.dirtied_ino_d = ALIGN(whiteout_ui->data_len, 8); + /* + * To avoid deadlock between space budget (holds ui_mutex and + * waits wb work) and writeback work(waits ui_mutex), do space + * budget before ubifs inodes locked. + */ + err = ubifs_budget_space(c, &wht_req); + if (err) { + iput(whiteout); + goto out_release; + } }
lock_4_inodes(old_dir, new_dir, new_inode, whiteout); @@ -1419,16 +1434,6 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry, }
if (whiteout) { - struct ubifs_budget_req wht_req = { .dirtied_ino = 1, - .dirtied_ino_d = \ - ALIGN(ubifs_inode(whiteout)->data_len, 8) }; - - err = ubifs_budget_space(c, &wht_req); - if (err) { - iput(whiteout); - goto out_release; - } - inc_nlink(whiteout); mark_inode_dirty(whiteout);