[RFC/PATCH 2/2] shmem: use lib/parser for mount options

[Randy Dunlap <randy.dunlap@oracle.com>]

Build-tested only.  I will run-test it, but I want to ask first:
Is there any trick to mounting/testing shmem/tmpfs?

Thanks.
---

From: Randy Dunlap <randy.dunlap@oracle.com>

Convert shmem (tmpfs) to use the in-kernel mount options parsing library.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
---
 mm/shmem.c |  150 +++++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 88 insertions(+), 62 deletions(-)

--- linux-2622-rc2.orig/mm/shmem.c
+++ linux-2622-rc2/mm/shmem.c
@@ -32,6 +32,7 @@
 #include <linux/mman.h>
 #include <linux/file.h>
 #include <linux/swap.h>
+#include <linux/parser.h>
 #include <linux/pagemap.h>
 #include <linux/string.h>
 #include <linux/slab.h>
@@ -84,6 +85,23 @@ enum sgp_type {
 	SGP_WRITE,	/* may exceed i_size, may allocate page */
 };
 
+enum {
+	Opt_size, Opt_nr_blocks, Opt_nr_inodes,
+	Opt_mode, Opt_uid, Opt_gid,
+	Opt_mpol, Opt_err,
+};
+
+static match_table_t tokens = {
+	{Opt_size,	"size=%u"},
+	{Opt_nr_blocks,	"nr_blocks=%u"},
+	{Opt_nr_inodes,	"nr_inodes=%u"},
+	{Opt_mode,	"mode=%u"},	/* not for remount */
+	{Opt_uid,	"uid=%u"},	/* not for remount */
+	{Opt_gid,	"gid=%u"},	/* not for remount */
+	{Opt_mpol,	"mpol=%s"},	/* various NUMA memory policy options */
+	{Opt_err,	NULL},
+};
+
 static int shmem_getpage(struct inode *inode, unsigned long idx,
 			 struct page **pagep, enum sgp_type sgp, int *type);
 
@@ -2113,92 +2131,100 @@ static struct export_operations shmem_ex
 
 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
 	gid_t *gid, unsigned long *blocks, unsigned long *inodes,
-	int *policy, nodemask_t *policy_nodes)
+	int *policy, nodemask_t *policy_nodes, int is_remount)
 {
-	char *this_char, *value, *rest;
+	char *rest;
+	substring_t args[MAX_OPT_ARGS];
+	char *p;
+	int option;
 
-	while (options != NULL) {
-		this_char = options;
-		for (;;) {
-			/*
-			 * NUL-terminate this option: unfortunately,
-			 * mount options form a comma-separated list,
-			 * but mpol's nodelist may also contain commas.
-			 */
-			options = strchr(options, ',');
-			if (options == NULL)
-				break;
-			options++;
-			if (!isdigit(*options)) {
-				options[-1] = '\0';
-				break;
-			}
-		}
-		if (!*this_char)
-			continue;
-		if ((value = strchr(this_char,'=')) != NULL) {
-			*value++ = 0;
-		} else {
-			printk(KERN_ERR
-			    "tmpfs: No value for mount option '%s'\n",
-			    this_char);
-			return 1;
-		}
+	if (!options)
+		return 0;
 
-		if (!strcmp(this_char,"size")) {
+	while ((p = strsep(&options, ",")) != NULL) {
+		int token;
+
+		if (!*p)
+			continue;
+		token = match_token(p, tokens, args);
+		switch (token) {
+		case Opt_size: {
 			unsigned long long size;
-			size = memparse(value,&rest);
+			size = memparse(args[0].from, &rest);
 			if (*rest == '%') {
 				size <<= PAGE_SHIFT;
 				size *= totalram_pages;
 				do_div(size, 100);
 				rest++;
 			}
-			if (*rest)
-				goto bad_val;
 			*blocks = size >> PAGE_CACHE_SHIFT;
-		} else if (!strcmp(this_char,"nr_blocks")) {
-			*blocks = memparse(value,&rest);
-			if (*rest)
-				goto bad_val;
-		} else if (!strcmp(this_char,"nr_inodes")) {
-			*inodes = memparse(value,&rest);
-			if (*rest)
-				goto bad_val;
-		} else if (!strcmp(this_char,"mode")) {
+			break;
+		}
+		case Opt_nr_blocks:
+			*blocks = memparse(args[0].from, &rest);
+			break;
+		case Opt_nr_inodes:
+			*inodes = memparse(args[0].from, &rest);
+			break;
+		case Opt_mode:
+			if (is_remount)		/* not valid on remount */
+				break;
 			if (!mode)
-				continue;
-			*mode = simple_strtoul(value,&rest,8);
-			if (*rest)
+				break;
+			if (match_int(&args[0], &option))
 				goto bad_val;
-		} else if (!strcmp(this_char,"uid")) {
+			*mode = option;
+			break;
+		case Opt_uid:
+			if (is_remount)		/* not valid on remount */
+				break;
 			if (!uid)
-				continue;
-			*uid = simple_strtoul(value,&rest,0);
-			if (*rest)
+				break;
+			if (match_int(&args[0], &option))
 				goto bad_val;
-		} else if (!strcmp(this_char,"gid")) {
+			*uid = option;
+			break;
+		case Opt_gid:
+			if (is_remount)		/* not valid on remount */
+				break;
 			if (!gid)
-				continue;
-			*gid = simple_strtoul(value,&rest,0);
-			if (*rest)
+				break;
+			if (match_int(&args[0], &option))
 				goto bad_val;
-		} else if (!strcmp(this_char,"mpol")) {
-			if (shmem_parse_mpol(value,policy,policy_nodes))
+			*gid = option;
+			break;
+		case Opt_mpol:
+			if (shmem_parse_mpol(args[0].from, policy, policy_nodes))
 				goto bad_val;
-		} else {
-			printk(KERN_ERR "tmpfs: Bad mount option %s\n",
-			       this_char);
+			break;
+		default:
+			printk(KERN_ERR "tmpfs: Bad mount option %s\n", p);
 			return 1;
+			break;
+		}
+
+		for (;;) {
+			/*
+			 * NUL-terminate this option: unfortunately,
+			 * mount options form a comma-separated list,
+			 * but mpol's nodelist may also contain commas.
+			 */
+			options = strchr(options, ',');
+			if (options == NULL)
+				break;
+			options++;
+			if (!isdigit(*options)) {
+				options[-1] = '\0';
+				break;
+			}
 		}
 	}
 	return 0;
 
 bad_val:
 	printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
-	       value, this_char);
+	       args[0].from, p);
 	return 1;
-
 }
 
 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
@@ -2213,7 +2239,7 @@ static int shmem_remount_fs(struct super
 	int error = -EINVAL;
 
 	if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
-				&max_inodes, &policy, &policy_nodes))
+				&max_inodes, &policy, &policy_nodes, 1))
 		return error;
 
 	spin_lock(&sbinfo->stat_lock);
@@ -2280,7 +2306,7 @@ static int shmem_fill_super(struct super
 		if (inodes > blocks)
 			inodes = blocks;
 		if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
-					&inodes, &policy, &policy_nodes))
+					&inodes, &policy, &policy_nodes, 0))
 			return -EINVAL;
 	}
 	sb->s_export_op = &shmem_export_ops;

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