[PATCH] dcache: report a Tasks-RCU quiescent state in dentry_kill()

I am constantly seeing the following warning on Meta's fleet:

  INFO: rcu_tasks detected stalls on tasks:
    native_queued_spin_lock_slowpath
    locked_inode_to_wb_and_lock_list
    inode_io_list_del
    evict
    __dentry_kill
    shrink_dentry_list
    shrink_dcache_tree
    d_invalidate
    btrfs_delete_subvolume
    btrfs_ioctl_snap_destroy
    btrfs_ioctl
    do_syscall_64

dentry_kill() is the common funnel for dentry teardown: dput(),
shrink_dentry_list() and shrink_dcache_tree() all reach it, once per
dentry, and its cond_resched() is the only reschedule point on that path.

cond_resched() is not an RCU-tasks quiescent state.

Use cond_resched_tasks_rcu_qs() so the teardown reports an RCU-tasks
quiescent state as it proceeds.

Fixes: 9c5f1d30199d ("dcache: move cond_resched() into the end of __dentry_kill()")
Cc: [email protected]
Signed-off-by: Breno Leitao <[email protected]>
---
 fs/dcache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 1b1a81f10da67..b89c8480b655b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -830,7 +830,7 @@ static struct dentry *dentry_kill(struct dentry *dentry)
 	if (dentry->d_op && dentry->d_op->d_release)
 		dentry->d_op->d_release(dentry);
 
-	cond_resched();
+	cond_resched_tasks_rcu_qs();
 	/* now that it's negative, ->d_parent is stable */
 	if (!IS_ROOT(dentry)) {
 		parent = dentry->d_parent;

---
base-commit: 5dd1818b15d98d4a20806cd00b1b40320b06004f
change-id: 20260918-dcache-task-rcu-qa-b4bcb13f1524

Best regards,
--  
Breno Leitao <[email protected]>