smb3: allow controlling maximum number of cached directories

Allow adjusting the maximum number of cached directories per share
(defaults to 16) via mount parm "max_cached_dirs"
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/cached_dir.c

@@ -18,7 +18,8 @@ static void smb2_close_cached_fid(struct kref *ref);
 
 static struct cached_fid *find_or_create_cached_dir(struct cached_fids *cfids,
 						    const char *path,
-						    bool lookup_only)
+						    bool lookup_only,
+						    __u32 max_cached_dirs)
 {
 	struct cached_fid *cfid;
 
@@ -43,7 +44,7 @@ static struct cached_fid *find_or_create_cached_dir(struct cached_fids *cfids,
 		spin_unlock(&cfids->cfid_list_lock);
 		return NULL;
 	}
-	if (cfids->num_entries >= MAX_CACHED_FIDS) {
+	if (cfids->num_entries >= max_cached_dirs) {
 		spin_unlock(&cfids->cfid_list_lock);
 		return NULL;
 	}
@@ -162,7 +163,7 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon,
 	if (!utf16_path)
 		return -ENOMEM;
 
-	cfid = find_or_create_cached_dir(cfids, path, lookup_only);
+	cfid = find_or_create_cached_dir(cfids, path, lookup_only, tcon->max_cached_dirs);
 	if (cfid == NULL) {
 		kfree(utf16_path);
 		return -ENOENT;

fs/smb/client/cached_dir.h

@@ -49,7 +49,7 @@ struct cached_fid {
 	struct cached_dirents dirents;
 };
 
-#define MAX_CACHED_FIDS 16
+/* default MAX_CACHED_FIDS is 16 */
 struct cached_fids {
 	/* Must be held when:
 	 * - accessing the cfids->entries list

fs/smb/client/cifsfs.c

@@ -699,6 +699,8 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 		seq_printf(s, ",snapshot=%llu", tcon->snapshot_time);
 	if (tcon->handle_timeout)
 		seq_printf(s, ",handletimeout=%u", tcon->handle_timeout);
+	if (tcon->max_cached_dirs != MAX_CACHED_FIDS)
+		seq_printf(s, ",max_cached_dirs=%u", tcon->max_cached_dirs);
 
 	/*
 	 * Display file and directory attribute timeout in seconds.

fs/smb/client/cifsglob.h

@@ -1210,6 +1210,7 @@ struct cifs_tcon {
 	__u32 max_chunks;
 	__u32 max_bytes_chunk;
 	__u32 max_bytes_copy;
+	__u32 max_cached_dirs;
 #ifdef CONFIG_CIFS_FSCACHE
 	u64 resource_id;		/* server resource id */
 	struct fscache_volume *fscache;	/* cookie for share */

fs/smb/client/connect.c

@@ -2657,6 +2657,7 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 	tcon->retry = ctx->retry;
 	tcon->nocase = ctx->nocase;
 	tcon->broken_sparse_sup = ctx->no_sparse;
+	tcon->max_cached_dirs = ctx->max_cached_dirs;
 	if (ses->server->capabilities & SMB2_GLOBAL_CAP_DIRECTORY_LEASING)
 		tcon->nohandlecache = ctx->nohandlecache;
 	else

fs/smb/client/fs_context.c

@@ -150,6 +150,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_u32("closetimeo", Opt_closetimeo),
 	fsparam_u32("echo_interval", Opt_echo_interval),
 	fsparam_u32("max_credits", Opt_max_credits),
+	fsparam_u32("max_cached_dirs", Opt_max_cached_dirs),
 	fsparam_u32("handletimeout", Opt_handletimeout),
 	fsparam_u64("snapshot", Opt_snapshot),
 	fsparam_u32("max_channels", Opt_max_channels),
@@ -1165,6 +1166,14 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		if (result.uint_32 > 1)
 			ctx->multichannel = true;
 		break;
+	case Opt_max_cached_dirs:
+		if (result.uint_32 < 1) {
+			cifs_errorf(fc, "%s: Invalid max_cached_dirs, needs to be 1 or more\n",
+				    __func__);
+			goto cifs_parse_mount_err;
+		}
+		ctx->max_cached_dirs = result.uint_32;
+		break;
 	case Opt_handletimeout:
 		ctx->handle_timeout = result.uint_32;
 		if (ctx->handle_timeout > SMB3_MAX_HANDLE_TIMEOUT) {
@@ -1592,7 +1601,7 @@ int smb3_init_fs_context(struct fs_context *fc)
 	ctx->acregmax = CIFS_DEF_ACTIMEO;
 	ctx->acdirmax = CIFS_DEF_ACTIMEO;
 	ctx->closetimeo = SMB3_DEF_DCLOSETIMEO;
-
+	ctx->max_cached_dirs = MAX_CACHED_FIDS;
 	/* Most clients set timeout to 0, allows server to use its default */
 	ctx->handle_timeout = 0; /* See MS-SMB2 spec section 2.2.14.2.12 */
 

fs/smb/client/fs_context.h

@@ -128,6 +128,7 @@ enum cifs_param {
 	Opt_closetimeo,
 	Opt_echo_interval,
 	Opt_max_credits,
+	Opt_max_cached_dirs,
 	Opt_snapshot,
 	Opt_max_channels,
 	Opt_handletimeout,
@@ -261,6 +262,7 @@ struct smb3_fs_context {
 	__u32 handle_timeout; /* persistent and durable handle timeout in ms */
 	unsigned int max_credits; /* smb3 max_credits 10 < credits < 60000 */
 	unsigned int max_channels;
+	unsigned int max_cached_dirs;
 	__u16 compression; /* compression algorithm 0xFFFF default 0=disabled */
 	bool rootfs:1; /* if it's a SMB root file system */
 	bool witness:1; /* use witness protocol */
@@ -287,7 +289,7 @@ extern void smb3_update_mnt_flags(struct cifs_sb_info *cifs_sb);
  */
 #define SMB3_MAX_DCLOSETIMEO (1 << 30)
 #define SMB3_DEF_DCLOSETIMEO (1 * HZ) /* even 1 sec enough to help eg open/write/close/open/read */
-
+#define MAX_CACHED_FIDS 16
 extern char *cifs_sanitize_prepath(char *prepath, gfp_t gfp);
 
 #endif