Commit 17d912d5 authored by Enzo Matsumiya's avatar Enzo Matsumiya Committed by Steve French
Browse files

smb: client: fix (remove) drop_dir_cache module parameter 



Being a module parameter, it's possible to do:

  # modprobe cifs drop_dir_cache=1

Which will lead to a crash, because cifs_tcp_ses_list hasn't been
initialized yet:

  [  168.242624] BUG: kernel NULL pointer dereference, address: 0000000000000010
  [  168.242952] #PF: supervisor read access in kernel mode
  [  168.243175] #PF: error_code(0x0000) - not-present page
  [  168.243394] PGD 0 P4D 0
  [  168.243524] Oops: Oops: 0000 [#1] SMP NOPTI
  [  168.243703] CPU: 2 UID: 0 PID: 1105 Comm: modprobe Not tainted 7.0.0-lku #5 PREEMPT(lazy)
  [  168.244054] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-2-g4f253b9b-prebuilt.qemu.org 04/01/2014
  [  168.244557] RIP: 0010:cifs_param_set_drop_dir_cache+0x7c/0x100 [cifs]
  ...
  [  168.248785] Call Trace:
  [  168.248915]  <TASK>
  [  168.249023]  parse_args+0x285/0x3a0
  [  168.249204]  ? __pfx_unknown_module_param_cb+0x10/0x10
  [  168.249448]  load_module+0x192b/0x1bb0
  [  168.249637]  ? __pfx_unknown_module_param_cb+0x10/0x10
  [  168.249882]  ? kernel_read_file+0x27d/0x2b0
  [  168.250088]  init_module_from_file+0xce/0xf0
  [  168.250291]  idempotent_init_module+0xfb/0x2f0
  [  168.250496]  __x64_sys_finit_module+0x5a/0xa0
  [  168.250694]  do_syscall_64+0xe0/0x5a0
  [  168.250863]  ? exc_page_fault+0x65/0x160
  [  168.251050]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  [  168.251284] RIP: 0033:0x7fcaa12b774d

Instead of fixing this with some kind of "is module initialized"
approach, this patch instead moves that functionality to procfs,
setting a write op for the existing open_dirs entry, where
writing a 0 to it will drop the cached directory entries.

Also make it available only when CONFIG_CIFS_DEBUG=y.

A small change needed now is to not call flush_delayed_work()
on invalidate_all_cached_dirs() when called from procfs (can't sleep in
that context).
So add a @sync arg to invalidate_all_cached_dirs() to control when to
flush the delayed works.

Fixes: dde6667f ("smb: client: add drop_dir_cache module parameter to invalidate cached dirents")
Signed-off-by: default avatarEnzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 2757ad3e

fs/smb/client/cached_dir.c

+3 −2
Original line number Diff line number Diff line
@@ -593,7 +593,7 @@ void close_all_cached_dirs(struct cifs_sb_info *cifs_sb) 
 * Invalidate all cached dirs when a TCON has been reset

 * due to a session loss.

 */

void invalidate_all_cached_dirs(struct cifs_tcon *tcon)

void invalidate_all_cached_dirs(struct cifs_tcon *tcon, bool sync)

{

	struct cached_fids *cfids = tcon->cfids;

	struct cached_fid *cfid, *q;
@@ -625,6 +625,7 @@ void invalidate_all_cached_dirs(struct cifs_tcon *tcon) 


	/* run laundromat unconditionally now as there might have been previously queued work */

	mod_delayed_work(cfid_put_wq, &cfids->laundromat_work, 0);

	if (sync)

		flush_delayed_work(&cfids->laundromat_work);

}

fs/smb/client/cached_dir.h

+1 −1
Original line number Diff line number Diff line
@@ -90,7 +90,7 @@ void close_cached_dir(struct cached_fid *cfid); 
void drop_cached_dir_by_name(const unsigned int xid, struct cifs_tcon *tcon,

			     const char *name, struct cifs_sb_info *cifs_sb);

void close_all_cached_dirs(struct cifs_sb_info *cifs_sb);

void invalidate_all_cached_dirs(struct cifs_tcon *tcon);

void invalidate_all_cached_dirs(struct cifs_tcon *tcon, bool sync);

bool cached_dir_lease_break(struct cifs_tcon *tcon, __u8 lease_key[16]);



#endif			/* _CACHED_DIR_H */

fs/smb/client/cifs_debug.c

+53 −3
Original line number Diff line number Diff line
@@ -306,6 +306,9 @@ static int cifs_debug_dirs_proc_show(struct seq_file *m, void *v) 
	LIST_HEAD(entry);



	seq_puts(m, "# Version:1\n");

#ifdef CONFIG_CIFS_DEBUG

	seq_puts(m, "# Write 0 to this file to drop all cached directory entries\n");

#endif /* CONFIG_CIFS_DEBUG */

	seq_puts(m, "# Format:\n");

	seq_puts(m, "# <tree id> <sess id> <persistent fid> <lease-key> <path>\n");
@@ -353,6 +356,51 @@ static int cifs_debug_dirs_proc_show(struct seq_file *m, void *v) 
	return 0;

}



#ifdef CONFIG_CIFS_DEBUG

static int cifs_debug_dirs_proc_open(struct inode *inode, struct file *file)

{

	return single_open(file, cifs_debug_dirs_proc_show, NULL);

}



/* Drop all cached directory entries across all CIFS mounts. */

static ssize_t cifs_debug_dirs_proc_write(struct file *file, const char __user *buffer,

					  size_t count, loff_t *ppos)

{

	int rc, v;



	rc = kstrtoint_from_user(buffer, count, 10, &v);

	if (rc)

		return rc;



	if (v == 0) {

		struct TCP_Server_Info *server;

		struct cifs_ses *ses;

		struct cifs_tcon *tcon;



		spin_lock(&cifs_tcp_ses_lock);

		list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {

			list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {

				if (cifs_ses_exiting(ses))

					continue;

				list_for_each_entry(tcon, &ses->tcon_list, tcon_list)

					invalidate_all_cached_dirs(tcon, false);

			}

		}

		spin_unlock(&cifs_tcp_ses_lock);

	}



	return count;

}



static const struct proc_ops cifs_debug_dirs_proc_ops = {

	.proc_open	= cifs_debug_dirs_proc_open,

	.proc_read	= seq_read,

	.proc_lseek	= seq_lseek,

	.proc_release	= single_release,

	.proc_write	= cifs_debug_dirs_proc_write,

};

#endif /* CONFIG_CIFS_DEBUG */



static __always_inline const char *compression_alg_str(__le16 alg)

{

	switch (alg) {
@@ -885,9 +933,11 @@ cifs_proc_init(void) 
	proc_create_single("open_files", 0400, proc_fs_cifs,

			cifs_debug_files_proc_show);



	proc_create_single("open_dirs", 0400, proc_fs_cifs,

			cifs_debug_dirs_proc_show);



#ifdef CONFIG_CIFS_DEBUG

	proc_create("open_dirs", 0600, proc_fs_cifs, &cifs_debug_dirs_proc_ops);

#else /* CONFIG_CIFS_DEBUG */

	proc_create_single("open_dirs", 0400, proc_fs_cifs, cifs_debug_dirs_proc_show);

#endif /* !CONFIG_CIFS_DEBUG */

	proc_create("Stats", 0644, proc_fs_cifs, &cifs_stats_proc_ops);

	proc_create("cifsFYI", 0644, proc_fs_cifs, &cifsFYI_proc_ops);

	proc_create("traceSMB", 0644, proc_fs_cifs, &traceSMB_proc_ops);

fs/smb/client/cifsfs.c

+0 −37
Original line number Diff line number Diff line
@@ -127,43 +127,6 @@ atomic64_t cifs_dircache_bytes_used = ATOMIC64_INIT(0); 
atomic_t cifs_sillycounter;

atomic_t cifs_tmpcounter;



/*

 * Write-only module parameter to drop all cached directory entries across

 * all CIFS mounts. Echo a non-zero value to trigger.

 */

static void cifs_drop_all_dir_caches(void)

{

	struct TCP_Server_Info *server;

	struct cifs_ses *ses;

	struct cifs_tcon *tcon;



	spin_lock(&cifs_tcp_ses_lock);

	list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {

		list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {

			if (cifs_ses_exiting(ses))

				continue;

			list_for_each_entry(tcon, &ses->tcon_list, tcon_list)

				invalidate_all_cached_dirs(tcon);

		}

	}

	spin_unlock(&cifs_tcp_ses_lock);

}



static int cifs_param_set_drop_dir_cache(const char *val, const struct kernel_param *kp)

{

	bool bv;

	int rc = kstrtobool(val, &bv);



	if (rc)

		return rc;

	if (bv)

		cifs_drop_all_dir_caches();

	return 0;

}



module_param_call(drop_dir_cache, cifs_param_set_drop_dir_cache, NULL, NULL, 0200);

MODULE_PARM_DESC(drop_dir_cache, "Write 1 to drop all cached directory entries across all CIFS mounts");



#ifdef CONFIG_CIFS_STATS2

unsigned int slow_rsp_threshold = 1;

module_param(slow_rsp_threshold, uint, 0644);

fs/smb/client/file.c

+1 −1
Original line number Diff line number Diff line
@@ -393,7 +393,7 @@ cifs_mark_open_files_invalid(struct cifs_tcon *tcon) 
	}

	spin_unlock(&tcon->open_file_lock);



	invalidate_all_cached_dirs(tcon);

	invalidate_all_cached_dirs(tcon, true);

	spin_lock(&tcon->tc_lock);

	if (tcon->status == TID_IN_FILES_INVALIDATE)

		tcon->status = TID_NEED_TCON;