Revert "proc: don't allow async path resolution of /proc/thread-self components"

stable inclusion
from stable-v5.10.162
commit 87cb08dc6b4f42a491e582d3ee79c30893681193
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7P7OH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=87cb08dc6b4f42a491e582d3ee79c30893681193

--------------------------------

[ Upstream commit 2587890b ]

This reverts commit 0d4370cf.

No longer needed, as the io-wq worker threads have the right identity.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nsanglipeng <sanglipeng1@jd.com>

fs/proc/self.c

@@ -20,7 +20,7 @@ static const char *proc_self_get_link(struct dentry *dentry,
 	 * Not currently supported. Once we can inherit all of struct pid,
 	 * we can allow this.
 	 */
-	if (current->flags & PF_IO_WORKER)
+	if (current->flags & PF_KTHREAD)
 		return ERR_PTR(-EOPNOTSUPP);
 
 	if (!tgid)

fs/proc/thread_self.c

@@ -17,13 +17,6 @@ static const char *proc_thread_self_get_link(struct dentry *dentry,
 	pid_t pid = task_pid_nr_ns(current, ns);
 	char *name;
 
-	/*
-	 * Not currently supported. Once we can inherit all of struct pid,
-	 * we can allow this.
-	 */
-	if (current->flags & PF_IO_WORKER)
-		return ERR_PTR(-EOPNOTSUPP);
-
 	if (!pid)
 		return ERR_PTR(-ENOENT);
 	name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);