cifs: Add new mount parameter "acdirmax" to allow caching directory metadata

nfs and cifs on Linux currently have a mount parameter "actimeo" to control
metadata (attribute) caching but cifs does not have additional mount
parameters to allow distinguishing between caching directory metadata
(e.g. needed to revalidate paths) and that for files.

Add new mount parameter "acdirmax" to allow caching metadata for
directories more loosely than file data.  NFS adjusts metadata
caching from acdirmin to acdirmax (and another two mount parms
for files) but to reduce complexity, it is safer to just introduce
the one mount parm to allow caching directories longer. The
defaults for acdirmax and actimeo (for cifs.ko) are conservative,
1 second (NFS defaults acdirmax to 60 seconds). For many workloads,
setting acdirmax to a higher value is safe and will improve
performance.  This patch leaves unchanged the default values
for caching metadata for files and directories but gives the
user more flexibility in adjusting them safely for their workload
via the new mount parm.

Signed-off-by: Steve French <[email protected]>
Reviewed-by: Ronnie Sahlberg <[email protected]>
Reviewed-By: Tom Talpey <[email protected]>

Author: Steve French

fs/cifs/cifsfs.c

@@ -637,8 +637,9 @@ 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);
-	/* convert actimeo and display it in seconds */
+	/* convert actimeo and directory attribute timeout and display in seconds */
 	seq_printf(s, ",actimeo=%lu", cifs_sb->ctx->actimeo / HZ);
+	seq_printf(s, ",acdirmax=%lu", cifs_sb->ctx->acdirmax / HZ);
 
 	if (tcon->ses->chan_max > 1)
 		seq_printf(s, ",multichannel,max_channels=%zu",

fs/cifs/connect.c

@@ -2278,6 +2278,8 @@ compare_mount_options(struct super_block *sb, struct cifs_mnt_data *mnt_data)
 
 	if (old->ctx->actimeo != new->ctx->actimeo)
 		return 0;
+	if (old->ctx->acdirmax != new->ctx->acdirmax)
+		return 0;
 
 	return 1;
 }

fs/cifs/fs_context.c

@@ -140,6 +140,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_u32("rsize", Opt_rsize),
 	fsparam_u32("wsize", Opt_wsize),
 	fsparam_u32("actimeo", Opt_actimeo),
+	fsparam_u32("acdirmax", Opt_acdirmax),
 	fsparam_u32("echo_interval", Opt_echo_interval),
 	fsparam_u32("max_credits", Opt_max_credits),
 	fsparam_u32("handletimeout", Opt_handletimeout),
@@ -936,6 +937,13 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 			goto cifs_parse_mount_err;
 		}
 		break;
+	case Opt_acdirmax:
+		ctx->acdirmax = HZ * result.uint_32;
+		if (ctx->acdirmax > CIFS_MAX_ACTIMEO) {
+			cifs_dbg(VFS, "acdirmax too large\n");
+			goto cifs_parse_mount_err;
+		}
+		break;
 	case Opt_echo_interval:
 		ctx->echo_interval = result.uint_32;
 		break;
@@ -1362,6 +1370,7 @@ int smb3_init_fs_context(struct fs_context *fc)
 	ctx->strict_io = true;
 
 	ctx->actimeo = CIFS_DEF_ACTIMEO;
+	ctx->acdirmax = CIFS_DEF_ACTIMEO;
 
 	/* 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/cifs/fs_context.h

@@ -118,6 +118,7 @@ enum cifs_param {
 	Opt_rsize,
 	Opt_wsize,
 	Opt_actimeo,
+	Opt_acdirmax,
 	Opt_echo_interval,
 	Opt_max_credits,
 	Opt_snapshot,
@@ -232,7 +233,8 @@ struct smb3_fs_context {
 	unsigned int wsize;
 	unsigned int min_offload;
 	bool sockopt_tcp_nodelay:1;
-	unsigned long actimeo; /* attribute cache timeout (jiffies) */
+	unsigned long actimeo; /* attribute cache timeout for files (jiffies) */
+	unsigned long acdirmax; /* attribute cache timeout for directories (jiffies) */
 	struct smb_version_operations *ops;
 	struct smb_version_values *vals;
 	char *prepath;