diff mbox series

[20/32] lnet: libcfs: debugfs file_operation should have an owner

Message ID 1659577097-19253-21-git-send-email-jsimmons@infradead.org (mailing list archive)
State New, archived
Headers show
Series lustre: Update to OpenSFS as of Aug 3 2022 | expand

Commit Message

James Simmons Aug. 4, 2022, 1:38 a.m. UTC 
From: Mr NeilBrown <neilb@suse.de>

If debugfs a file is open when unloading the libcfs/lnet module, it
produces a kernel Oops (debugfs file_operations callbacks no longer
exist).

Crash generated with routerstat (/sys/kernel/debug/lnet/stats):
[ 1449.750396] IP: [<ffffffffab24e093>] SyS_lseek+0x83/0x100
[ 1449.750412] PGD 9fa14067 PUD 9fa16067 PMD d4e5d067 PTE 0
[ 1449.750428] Oops: 0000 [#1] SMP
[ 1449.750883]  [<ffffffffab7aaf92>] system_call_fastpath+0x25/0x2a
[ 1449.750897]  [<ffffffffab7aaed5>] ?
system_call_after_swapgs+0xa2/0x13a

This patch adds an owner to debugfs file_operation for libcfs and
lnet_router entries (/sys/kernel/debug/lnet/*).

The following behavior is expected:
$ modprobe lustre
$ routerstat 10 > /dev/null &
$ lustre_rmmod
rmmod: ERROR: Module lnet is in use
Can't read statfile (ENODEV)
[1]+  Exit 1                  routerstat 10 > /dev/null
$ lustre_rmmod

Note that the allocated 'struct file_operations' cannot be freed until
the module_exit() function is called, as files could still be open
until then.

WC-bug-id: https://jira.whamcloud.com/browse/LU-15759
Lustre-commit: b2dfb4457f0f1e56f ("LU-15759 libcfs: debugfs file_operation should have an owner")
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Reviewed-on: https://review.whamcloud.com/47335
Reviewed-by: Etienne AUJAMES <eaujames@ddn.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 include/linux/libcfs/libcfs.h |  4 +++-
 include/linux/lnet/lib-lnet.h |  1 +
 net/lnet/libcfs/module.c      | 43 ++++++++++++++++++++++++++++++++++++-------
 net/lnet/lnet/module.c        |  1 +
 net/lnet/lnet/router_proc.c   | 10 +++++++++-
 5 files changed, 50 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/include/linux/libcfs/libcfs.h b/include/linux/libcfs/libcfs.h
index b59ef9b..e29b007 100644
--- a/include/linux/libcfs/libcfs.h
+++ b/include/linux/libcfs/libcfs.h
@@ -57,8 +57,10 @@  static inline int notifier_from_ioctl_errno(int err)
 
 extern struct workqueue_struct *cfs_rehash_wq;
 
-void lnet_insert_debugfs(struct ctl_table *table);
+void lnet_insert_debugfs(struct ctl_table *table, struct module *mod,
+			 void **statep);
 void lnet_remove_debugfs(struct ctl_table *table);
+void lnet_debugfs_fini(void **statep);
 
 int debugfs_doint(struct ctl_table *table, int write,
 		  void __user *buffer, size_t *lenp, loff_t *ppos);
diff --git a/include/linux/lnet/lib-lnet.h b/include/linux/lnet/lib-lnet.h
index 5a83190..57c8dc2 100644
--- a/include/linux/lnet/lib-lnet.h
+++ b/include/linux/lnet/lib-lnet.h
@@ -569,6 +569,7 @@  unsigned int lnet_nid_cpt_hash(struct lnet_nid *nid,
 
 int lnet_lib_init(void);
 void lnet_lib_exit(void);
+void lnet_router_exit(void);
 
 void lnet_mt_event_handler(struct lnet_event *event);
 
diff --git a/net/lnet/libcfs/module.c b/net/lnet/libcfs/module.c
index a249bdd..a126683 100644
--- a/net/lnet/libcfs/module.c
+++ b/net/lnet/libcfs/module.c
@@ -746,19 +746,23 @@  static ssize_t lnet_debugfs_write(struct file *filp, const char __user *buf,
 	.llseek		= default_llseek,
 };
 
-static const struct file_operations *lnet_debugfs_fops_select(umode_t mode)
+static const struct file_operations *
+lnet_debugfs_fops_select(umode_t mode, const struct file_operations state[3])
 {
 	if (!(mode & 0222))
-		return &lnet_debugfs_file_operations_ro;
+		return &state[0];
 
 	if (!(mode & 0444))
-		return &lnet_debugfs_file_operations_wo;
+		return &state[1];
 
-	return &lnet_debugfs_file_operations_rw;
+	return &state[2];
 }
 
-void lnet_insert_debugfs(struct ctl_table *table)
+void lnet_insert_debugfs(struct ctl_table *table, struct module *mod,
+			 void **statep)
 {
+	struct file_operations *state = *statep;
+
 	if (!lnet_debugfs_root)
 		lnet_debugfs_root = debugfs_create_dir("lnet", NULL);
 
@@ -766,6 +770,19 @@  void lnet_insert_debugfs(struct ctl_table *table)
 	if (IS_ERR_OR_NULL(lnet_debugfs_root))
 		return;
 
+	if (!state) {
+		state = kmalloc(3 * sizeof(*state), GFP_KERNEL);
+		if (!state)
+			return;
+		state[0] = lnet_debugfs_file_operations_ro;
+		state[0].owner = mod;
+		state[1] = lnet_debugfs_file_operations_wo;
+		state[1].owner = mod;
+		state[2] = lnet_debugfs_file_operations_rw;
+		state[2].owner = mod;
+		*statep = state;
+	}
+
 	/*
 	 * We don't save the dentry returned because we don't call
 	 * debugfs_remove() but rather remove_recursive()
@@ -773,10 +790,18 @@  void lnet_insert_debugfs(struct ctl_table *table)
 	for (; table && table->procname; table++)
 		debugfs_create_file(table->procname, table->mode,
 				    lnet_debugfs_root, table,
-				    lnet_debugfs_fops_select(table->mode));
+				    lnet_debugfs_fops_select(table->mode,
+							     (const struct file_operations *)state));
 }
 EXPORT_SYMBOL_GPL(lnet_insert_debugfs);
 
+void lnet_debugfs_fini(void **state)
+{
+	kfree(*state);
+	*state = NULL;
+}
+EXPORT_SYMBOL_GPL(lnet_debugfs_fini);
+
 static void lnet_insert_debugfs_links(
 	const struct lnet_debugfs_symlink_def *symlinks)
 {
@@ -801,6 +826,8 @@  void lnet_remove_debugfs(struct ctl_table *table)
 static DEFINE_MUTEX(libcfs_startup);
 static int libcfs_active;
 
+static void *debugfs_state;
+
 int libcfs_setup(void)
 {
 	int rc = -EINVAL;
@@ -855,7 +882,7 @@  static int libcfs_init(void)
 {
 	int rc;
 
-	lnet_insert_debugfs(lnet_table);
+	lnet_insert_debugfs(lnet_table, THIS_MODULE, &debugfs_state);
 	if (!IS_ERR_OR_NULL(lnet_debugfs_root))
 		lnet_insert_debugfs_links(lnet_debugfs_symlinks);
 
@@ -875,6 +902,8 @@  static void libcfs_exit(void)
 	debugfs_remove_recursive(lnet_debugfs_root);
 	lnet_debugfs_root = NULL;
 
+	lnet_debugfs_fini(&debugfs_state);
+
 	if (cfs_rehash_wq)
 		destroy_workqueue(cfs_rehash_wq);
 
diff --git a/net/lnet/lnet/module.c b/net/lnet/lnet/module.c
index aba9589..9d7b39a 100644
--- a/net/lnet/lnet/module.c
+++ b/net/lnet/lnet/module.c
@@ -271,6 +271,7 @@  static void __exit lnet_exit(void)
 						&lnet_ioctl_handler);
 	LASSERT(!rc);
 
+	lnet_router_exit();
 	lnet_lib_exit();
 }
 
diff --git a/net/lnet/lnet/router_proc.c b/net/lnet/lnet/router_proc.c
index f231da1..689670a 100644
--- a/net/lnet/lnet/router_proc.c
+++ b/net/lnet/lnet/router_proc.c
@@ -888,12 +888,20 @@  static int proc_lnet_portal_rotor(struct ctl_table *table, int write,
 	}
 };
 
+static void *debugfs_state;
+
 void lnet_router_debugfs_init(void)
 {
-	lnet_insert_debugfs(lnet_table);
+	lnet_insert_debugfs(lnet_table, THIS_MODULE,
+			    &debugfs_state);
 }
 
 void lnet_router_debugfs_fini(void)
 {
 	lnet_remove_debugfs(lnet_table);
 }
+
+void lnet_router_exit(void)
+{
+	lnet_debugfs_fini(&debugfs_state);
+}