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authorZhihao Cheng <chengzhihao1@huawei.com>2021-12-27 11:22:33 +0800
committerRichard Weinberger <richard@nod.at>2022-01-09 21:33:25 +0100
commitafd427048047e8efdedab30e8888044e2be5aa9c (patch)
tree15ff09683065abc23e7ce6a240432cfc1c556eb7 /fs/ubifs
parent40a8f0d5e7b3999f096570edab71c345da812e3e (diff)
ubifs: Fix deadlock in concurrent rename whiteout and inode writeback
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>
Diffstat (limited to 'fs/ubifs')
-rw-r--r--fs/ubifs/dir.c25
1 files changed, 15 insertions, 10 deletions
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);