1 files changed, 372 insertions, 0 deletions
diff --git a/fs/aufs/wkq.c b/fs/aufs/wkq.c
new file mode 100644
index 000000000000..4d66bb2dc657
--- /dev/null
+++ b/fs/aufs/wkq.c
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2020 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * workqueue for asynchronous/super-io operations
+ * todo: try new credential scheme
+ */
+
+#include <linux/module.h>
+#include "aufs.h"
+
+/* internal workqueue named AUFS_WKQ_NAME */
+
+static struct workqueue_struct *au_wkq;
+
+struct au_wkinfo {
+	struct work_struct wk;
+	struct kobject *kobj;
+
+	unsigned int flags; /* see wkq.h */
+
+	au_wkq_func_t func;
+	void *args;
+
+#ifdef CONFIG_LOCKDEP
+	int dont_check;
+	struct held_lock **hlock;
+#endif
+
+	struct completion *comp;
+};
+
+/* ---------------------------------------------------------------------- */
+/*
+ * Aufs passes some operations to the workqueue such as the internal copyup.
+ * This scheme looks rather unnatural for LOCKDEP debugging feature, since the
+ * job run by workqueue depends upon the locks acquired in the other task.
+ * Delegating a small operation to the workqueue, aufs passes its lockdep
+ * information too. And the job in the workqueue restores the info in order to
+ * pretend as if it acquired those locks. This is just to make LOCKDEP work
+ * correctly and expectedly.
+ */
+
+#ifndef CONFIG_LOCKDEP
+AuStubInt0(au_wkq_lockdep_alloc, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_free, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_pre, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_post, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_init, struct au_wkinfo *wkinfo);
+#else
+static void au_wkq_lockdep_init(struct au_wkinfo *wkinfo)
+{
+	wkinfo->hlock = NULL;
+	wkinfo->dont_check = 0;
+}
+
+/*
+ * 1: matched
+ * 0: unmatched
+ */
+static int au_wkq_lockdep_test(struct lock_class_key *key, const char *name)
+{
+	static DEFINE_SPINLOCK(spin);
+	static struct {
+		char *name;
+		struct lock_class_key *key;
+	} a[] = {
+		{ .name = "&sbinfo->si_rwsem" },
+		{ .name = "&finfo->fi_rwsem" },
+		{ .name = "&dinfo->di_rwsem" },
+		{ .name = "&iinfo->ii_rwsem" }
+	};
+	static int set;
+	int i;
+
+	/* lockless read from 'set.' see below */
+	if (set == ARRAY_SIZE(a)) {
+		for (i = 0; i < ARRAY_SIZE(a); i++)
+			if (a[i].key == key)
+				goto match;
+		goto unmatch;
+	}
+
+	spin_lock(&spin);
+	if (set)
+		for (i = 0; i < ARRAY_SIZE(a); i++)
+			if (a[i].key == key) {
+				spin_unlock(&spin);
+				goto match;
+			}
+	for (i = 0; i < ARRAY_SIZE(a); i++) {
+		if (a[i].key) {
+			if (unlikely(a[i].key == key)) { /* rare but possible */
+				spin_unlock(&spin);
+				goto match;
+			} else
+				continue;
+		}
+		if (strstr(a[i].name, name)) {
+			/*
+			 * the order of these three lines is important for the
+			 * lockless read above.
+			 */
+			a[i].key = key;
+			spin_unlock(&spin);
+			set++;
+			/* AuDbg("%d, %s\n", set, name); */
+			goto match;
+		}
+	}
+	spin_unlock(&spin);
+	goto unmatch;
+
+match:
+	return 1;
+unmatch:
+	return 0;
+}
+
+static int au_wkq_lockdep_alloc(struct au_wkinfo *wkinfo)
+{
+	int err, n;
+	struct task_struct *curr;
+	struct held_lock **hl, *held_locks, *p;
+
+	err = 0;
+	curr = current;
+	wkinfo->dont_check = lockdep_recursing(curr);
+	if (wkinfo->dont_check)
+		goto out;
+	n = curr->lockdep_depth;
+	if (!n)
+		goto out;
+
+	err = -ENOMEM;
+	wkinfo->hlock = kmalloc_array(n + 1, sizeof(*wkinfo->hlock), GFP_NOFS);
+	if (unlikely(!wkinfo->hlock))
+		goto out;
+
+	err = 0;
+#if 0 /* left for debugging */
+	if (0 && au_debug_test())
+		lockdep_print_held_locks(curr);
+#endif
+	held_locks = curr->held_locks;
+	hl = wkinfo->hlock;
+	while (n--) {
+		p = held_locks++;
+		if (au_wkq_lockdep_test(p->instance->key, p->instance->name))
+			*hl++ = p;
+	}
+	*hl = NULL;
+
+out:
+	return err;
+}
+
+static void au_wkq_lockdep_free(struct au_wkinfo *wkinfo)
+{
+	au_kfree_try_rcu(wkinfo->hlock);
+}
+
+static void au_wkq_lockdep_pre(struct au_wkinfo *wkinfo)
+{
+	struct held_lock *p, **hl = wkinfo->hlock;
+	int subclass;
+
+	if (wkinfo->dont_check)
+		lockdep_off();
+	if (!hl)
+		return;
+	while ((p = *hl++)) { /* assignment */
+		subclass = lockdep_hlock_class(p)->subclass;
+		/* AuDbg("%s, %d\n", p->instance->name, subclass); */
+		if (p->read)
+			rwsem_acquire_read(p->instance, subclass, 0,
+					   /*p->acquire_ip*/_RET_IP_);
+		else
+			rwsem_acquire(p->instance, subclass, 0,
+				      /*p->acquire_ip*/_RET_IP_);
+	}
+}
+
+static void au_wkq_lockdep_post(struct au_wkinfo *wkinfo)
+{
+	struct held_lock *p, **hl = wkinfo->hlock;
+
+	if (wkinfo->dont_check)
+		lockdep_on();
+	if (!hl)
+		return;
+	while ((p = *hl++)) /* assignment */
+		rwsem_release(p->instance, /*p->acquire_ip*/_RET_IP_);
+}
+#endif
+
+static void wkq_func(struct work_struct *wk)
+{
+	struct au_wkinfo *wkinfo = container_of(wk, struct au_wkinfo, wk);
+
+	AuDebugOn(!uid_eq(current_fsuid(), GLOBAL_ROOT_UID));
+	AuDebugOn(rlimit(RLIMIT_FSIZE) != RLIM_INFINITY);
+
+	au_wkq_lockdep_pre(wkinfo);
+	wkinfo->func(wkinfo->args);
+	au_wkq_lockdep_post(wkinfo);
+	if (au_ftest_wkq(wkinfo->flags, WAIT))
+		complete(wkinfo->comp);
+	else {
+		kobject_put(wkinfo->kobj);
+		module_put(THIS_MODULE); /* todo: ?? */
+		au_kfree_rcu(wkinfo);
+	}
+}
+
+/*
+ * Since struct completion is large, try allocating it dynamically.
+ */
+#define AuWkqCompDeclare(name)	struct completion *comp = NULL
+
+static int au_wkq_comp_alloc(struct au_wkinfo *wkinfo, struct completion **comp)
+{
+	*comp = kmalloc(sizeof(**comp), GFP_NOFS);
+	if (*comp) {
+		init_completion(*comp);
+		wkinfo->comp = *comp;
+		return 0;
+	}
+	return -ENOMEM;
+}
+
+static void au_wkq_comp_free(struct completion *comp)
+{
+	au_kfree_rcu(comp);
+}
+
+static void au_wkq_run(struct au_wkinfo *wkinfo)
+{
+	if (au_ftest_wkq(wkinfo->flags, NEST)) {
+		if (au_wkq_test()) {
+			AuWarn1("wkq from wkq, unless silly-rename on NFS,"
+				" due to a dead dir by UDBA,"
+				" or async xino write?\n");
+			AuDebugOn(au_ftest_wkq(wkinfo->flags, WAIT));
+		}
+	} else
+		au_dbg_verify_kthread();
+
+	if (au_ftest_wkq(wkinfo->flags, WAIT)) {
+		INIT_WORK_ONSTACK(&wkinfo->wk, wkq_func);
+		queue_work(au_wkq, &wkinfo->wk);
+	} else {
+		INIT_WORK(&wkinfo->wk, wkq_func);
+		schedule_work(&wkinfo->wk);
+	}
+}
+
+/*
+ * Be careful. It is easy to make deadlock happen.
+ * processA: lock, wkq and wait
+ * processB: wkq and wait, lock in wkq
+ * --> deadlock
+ */
+int au_wkq_do_wait(unsigned int flags, au_wkq_func_t func, void *args)
+{
+	int err;
+	AuWkqCompDeclare(comp);
+	struct au_wkinfo wkinfo = {
+		.flags	= flags,
+		.func	= func,
+		.args	= args
+	};
+
+	err = au_wkq_comp_alloc(&wkinfo, &comp);
+	if (unlikely(err))
+		goto out;
+	err = au_wkq_lockdep_alloc(&wkinfo);
+	if (unlikely(err))
+		goto out_comp;
+	if (!err) {
+		au_wkq_run(&wkinfo);
+		/* no timeout, no interrupt */
+		wait_for_completion(wkinfo.comp);
+	}
+	au_wkq_lockdep_free(&wkinfo);
+
+out_comp:
+	au_wkq_comp_free(comp);
+out:
+	destroy_work_on_stack(&wkinfo.wk);
+	return err;
+}
+
+/*
+ * Note: dget/dput() in func for aufs dentries are not supported. It will be a
+ * problem in a concurrent umounting.
+ */
+int au_wkq_nowait(au_wkq_func_t func, void *args, struct super_block *sb,
+		  unsigned int flags)
+{
+	int err;
+	struct au_wkinfo *wkinfo;
+
+	atomic_inc(&au_sbi(sb)->si_nowait.nw_len);
+
+	/*
+	 * wkq_func() must free this wkinfo.
+	 * it highly depends upon the implementation of workqueue.
+	 */
+	err = 0;
+	wkinfo = kmalloc(sizeof(*wkinfo), GFP_NOFS);
+	if (wkinfo) {
+		wkinfo->kobj = &au_sbi(sb)->si_kobj;
+		wkinfo->flags = flags & ~AuWkq_WAIT;
+		wkinfo->func = func;
+		wkinfo->args = args;
+		wkinfo->comp = NULL;
+		au_wkq_lockdep_init(wkinfo);
+		kobject_get(wkinfo->kobj);
+		__module_get(THIS_MODULE); /* todo: ?? */
+
+		au_wkq_run(wkinfo);
+	} else {
+		err = -ENOMEM;
+		au_nwt_done(&au_sbi(sb)->si_nowait);
+	}
+
+	return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_nwt_init(struct au_nowait_tasks *nwt)
+{
+	atomic_set(&nwt->nw_len, 0);
+	/* smp_mb(); */ /* atomic_set */
+	init_waitqueue_head(&nwt->nw_wq);
+}
+
+void au_wkq_fin(void)
+{
+	destroy_workqueue(au_wkq);
+}
+
+int __init au_wkq_init(void)
+{
+	int err;
+
+	err = 0;
+	au_wkq = alloc_workqueue(AUFS_WKQ_NAME, 0, WQ_DFL_ACTIVE);
+	if (IS_ERR(au_wkq))
+		err = PTR_ERR(au_wkq);
+	else if (!au_wkq)
+		err = -ENOMEM;
+
+	return err;
+}