mount options: fix tmpfs

Add .show_options super operation to tmpfs.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 136 insertions, 65 deletions

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index f3c51899117f..8d5fb36ea047 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -30,9 +30,12 @@ struct shmem_sb_info {
         unsigned long free_blocks;  /* How many are left for allocation */
         unsigned long max_inodes;   /* How many inodes are allowed */
         unsigned long free_inodes;  /* How many are left for allocation */
+        spinlock_t stat_lock;       /* Serialize shmem_sb_info changes */
+        uid_t uid;                  /* Mount uid for root directory */
+        gid_t gid;                  /* Mount gid for root directory */
+        mode_t mode;                /* Mount mode for root directory */
         int policy;                 /* Default NUMA memory alloc policy */
         nodemask_t policy_nodes;    /* nodemask for preferred and bind */
-        spinlock_t    stat_lock;
 };
 
 static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
diff --git a/mm/shmem.c b/mm/shmem.c
index 85bed948fafc..2f961a6dbf57 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -49,6 +49,7 @@
 #include <linux/ctype.h>
 #include <linux/migrate.h>
 #include <linux/highmem.h>
+#include <linux/seq_file.h>
 
 #include <asm/uaccess.h>
 #include <asm/div64.h>
@@ -84,6 +85,16 @@ enum sgp_type {
         SGP_WRITE,      /* may exceed i_size, may allocate page */
 };
 
+static unsigned long shmem_default_max_blocks(void)
+{
+        return totalram_pages / 2;
+}
+
+static unsigned long shmem_default_max_inodes(void)
+{
+        return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
+}
+
 static int shmem_getpage(struct inode *inode, unsigned long idx,
                          struct page **pagep, enum sgp_type sgp, int *type);
 
@@ -1068,7 +1079,8 @@ redirty:
 }
 
 #ifdef CONFIG_NUMA
-static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
+#ifdef CONFIG_TMPFS
+static int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
 {
         char *nodelist = strchr(value, ':');
         int err = 1;
@@ -1117,6 +1129,42 @@ out:
         return err;
 }
 
+static void shmem_show_mpol(struct seq_file *seq, int policy,
+                            const nodemask_t policy_nodes)
+{
+        char *policy_string;
+
+        switch (policy) {
+        case MPOL_PREFERRED:
+                policy_string = "prefer";
+                break;
+        case MPOL_BIND:
+                policy_string = "bind";
+                break;
+        case MPOL_INTERLEAVE:
+                policy_string = "interleave";
+                break;
+        default:
+                /* MPOL_DEFAULT */
+                return;
+        }
+
+        seq_printf(seq, ",mpol=%s", policy_string);
+
+        if (policy != MPOL_INTERLEAVE ||
+            !nodes_equal(policy_nodes, node_states[N_HIGH_MEMORY])) {
+                char buffer[64];
+                int len;
+
+                len = nodelist_scnprintf(buffer, sizeof(buffer), policy_nodes);
+                if (len < sizeof(buffer))
+                        seq_printf(seq, ":%s", buffer);
+                else
+                        seq_printf(seq, ":?");
+        }
+}
+#endif /* CONFIG_TMPFS */
+
 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
                         struct shmem_inode_info *info, unsigned long idx)
 {
@@ -1148,13 +1196,20 @@ static struct page *shmem_alloc_page(gfp_t gfp,
         mpol_free(pvma.vm_policy);
         return page;
 }
-#else
+#else /* !CONFIG_NUMA */
+#ifdef CONFIG_TMPFS
 static inline int shmem_parse_mpol(char *value, int *policy,
                                                 nodemask_t *policy_nodes)
 {
         return 1;
 }
 
+static inline void shmem_show_mpol(struct seq_file *seq, int policy,
+                            const nodemask_t policy_nodes)
+{
+}
+#endif /* CONFIG_TMPFS */
+
 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
                         struct shmem_inode_info *info, unsigned long idx)
 {
@@ -1166,7 +1221,7 @@ static inline struct page *shmem_alloc_page(gfp_t gfp,
 {
         return alloc_page(gfp);
 }
-#endif
+#endif /* CONFIG_NUMA */
 
 /*
  * shmem_getpage - either get the page from swap or allocate a new one
@@ -2077,9 +2132,8 @@ static const struct export_operations shmem_export_ops = {
         .fh_to_dentry   = shmem_fh_to_dentry,
 };
 
-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)
+static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
+                               bool remount)
 {
         char *this_char, *value, *rest;
 
@@ -2122,35 +2176,37 @@ static int shmem_parse_options(char *options, int *mode, uid_t *uid,
                         }
                         if (*rest)
                                 goto bad_val;
-                        *blocks = DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
+                        sbinfo->max_blocks =
+                                DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
                 } else if (!strcmp(this_char,"nr_blocks")) {
-                        *blocks = memparse(value,&rest);
+                        sbinfo->max_blocks = memparse(value, &rest);
                         if (*rest)
                                 goto bad_val;
                 } else if (!strcmp(this_char,"nr_inodes")) {
-                        *inodes = memparse(value,&rest);
+                        sbinfo->max_inodes = memparse(value, &rest);
                         if (*rest)
                                 goto bad_val;
                 } else if (!strcmp(this_char,"mode")) {
-                        if (!mode)
+                        if (remount)
                                 continue;
-                        *mode = simple_strtoul(value,&rest,8);
+                        sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
                         if (*rest)
                                 goto bad_val;
                 } else if (!strcmp(this_char,"uid")) {
-                        if (!uid)
+                        if (remount)
                                 continue;
-                        *uid = simple_strtoul(value,&rest,0);
+                        sbinfo->uid = simple_strtoul(value, &rest, 0);
                         if (*rest)
                                 goto bad_val;
                 } else if (!strcmp(this_char,"gid")) {
-                        if (!gid)
+                        if (remount)
                                 continue;
-                        *gid = simple_strtoul(value,&rest,0);
+                        sbinfo->gid = simple_strtoul(value, &rest, 0);
                         if (*rest)
                                 goto bad_val;
                 } else if (!strcmp(this_char,"mpol")) {
-                        if (shmem_parse_mpol(value,policy,policy_nodes))
+                        if (shmem_parse_mpol(value, &sbinfo->policy,
+                                             &sbinfo->policy_nodes))
                                 goto bad_val;
                 } else {
                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
@@ -2170,24 +2226,20 @@ bad_val:
 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
 {
         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
-        unsigned long max_blocks = sbinfo->max_blocks;
-        unsigned long max_inodes = sbinfo->max_inodes;
-        int policy = sbinfo->policy;
-        nodemask_t policy_nodes = sbinfo->policy_nodes;
+        struct shmem_sb_info config = *sbinfo;
         unsigned long blocks;
         unsigned long inodes;
         int error = -EINVAL;
 
-        if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
-                                &max_inodes, &policy, &policy_nodes))
+        if (shmem_parse_options(data, &config, true))
                 return error;
 
         spin_lock(&sbinfo->stat_lock);
         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
-        if (max_blocks < blocks)
+        if (config.max_blocks < blocks)
                 goto out;
-        if (max_inodes < inodes)
+        if (config.max_inodes < inodes)
                 goto out;
         /*
          * Those tests also disallow limited->unlimited while any are in
@@ -2195,23 +2247,42 @@ static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
          * but we must separately disallow unlimited->limited, because
          * in that case we have no record of how much is already in use.
          */
-        if (max_blocks && !sbinfo->max_blocks)
+        if (config.max_blocks && !sbinfo->max_blocks)
                 goto out;
-        if (max_inodes && !sbinfo->max_inodes)
+        if (config.max_inodes && !sbinfo->max_inodes)
                 goto out;
 
         error = 0;
-        sbinfo->max_blocks  = max_blocks;
-        sbinfo->free_blocks = max_blocks - blocks;
-        sbinfo->max_inodes  = max_inodes;
-        sbinfo->free_inodes = max_inodes - inodes;
-        sbinfo->policy = policy;
-        sbinfo->policy_nodes = policy_nodes;
+        sbinfo->max_blocks  = config.max_blocks;
+        sbinfo->free_blocks = config.max_blocks - blocks;
+        sbinfo->max_inodes  = config.max_inodes;
+        sbinfo->free_inodes = config.max_inodes - inodes;
+        sbinfo->policy      = config.policy;
+        sbinfo->policy_nodes = config.policy_nodes;
 out:
         spin_unlock(&sbinfo->stat_lock);
         return error;
 }
-#endif
+
+static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+        struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
+
+        if (sbinfo->max_blocks != shmem_default_max_blocks())
+                seq_printf(seq, ",size=%luk",
+                        sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
+        if (sbinfo->max_inodes != shmem_default_max_inodes())
+                seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
+        if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
+                seq_printf(seq, ",mode=%03o", sbinfo->mode);
+        if (sbinfo->uid != 0)
+                seq_printf(seq, ",uid=%u", sbinfo->uid);
+        if (sbinfo->gid != 0)
+                seq_printf(seq, ",gid=%u", sbinfo->gid);
+        shmem_show_mpol(seq, sbinfo->policy, sbinfo->policy_nodes);
+        return 0;
+}
+#endif /* CONFIG_TMPFS */
 
 static void shmem_put_super(struct super_block *sb)
 {
@@ -2224,15 +2295,23 @@ static int shmem_fill_super(struct super_block *sb,
 {
         struct inode *inode;
         struct dentry *root;
-        int mode   = S_IRWXUGO | S_ISVTX;
-        uid_t uid = current->fsuid;
-        gid_t gid = current->fsgid;
-        int err = -ENOMEM;
         struct shmem_sb_info *sbinfo;
-        unsigned long blocks = 0;
-        unsigned long inodes = 0;
-        int policy = MPOL_DEFAULT;
-        nodemask_t policy_nodes = node_states[N_HIGH_MEMORY];
+        int err = -ENOMEM;
+
+        /* Round up to L1_CACHE_BYTES to resist false sharing */
+        sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
+                                L1_CACHE_BYTES), GFP_KERNEL);
+        if (!sbinfo)
+                return -ENOMEM;
+
+        sbinfo->max_blocks = 0;
+        sbinfo->max_inodes = 0;
+        sbinfo->mode = S_IRWXUGO | S_ISVTX;
+        sbinfo->uid = current->fsuid;
+        sbinfo->gid = current->fsgid;
+        sbinfo->policy = MPOL_DEFAULT;
+        sbinfo->policy_nodes = node_states[N_HIGH_MEMORY];
+        sb->s_fs_info = sbinfo;
 
 #ifdef CONFIG_TMPFS
         /*
@@ -2241,34 +2320,22 @@ static int shmem_fill_super(struct super_block *sb,
          * but the internal instance is left unlimited.
          */
         if (!(sb->s_flags & MS_NOUSER)) {
-                blocks = totalram_pages / 2;
-                inodes = totalram_pages - totalhigh_pages;
-                if (inodes > blocks)
-                        inodes = blocks;
-                if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
-                                        &inodes, &policy, &policy_nodes))
-                        return -EINVAL;
+                sbinfo->max_blocks = shmem_default_max_blocks();
+                sbinfo->max_inodes = shmem_default_max_inodes();
+                if (shmem_parse_options(data, sbinfo, false)) {
+                        err = -EINVAL;
+                        goto failed;
+                }
         }
         sb->s_export_op = &shmem_export_ops;
 #else
         sb->s_flags |= MS_NOUSER;
 #endif
 
-        /* Round up to L1_CACHE_BYTES to resist false sharing */
-        sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
-                                L1_CACHE_BYTES), GFP_KERNEL);
-        if (!sbinfo)
-                return -ENOMEM;
-
         spin_lock_init(&sbinfo->stat_lock);
-        sbinfo->max_blocks = blocks;
-        sbinfo->free_blocks = blocks;
-        sbinfo->max_inodes = inodes;
-        sbinfo->free_inodes = inodes;
-        sbinfo->policy = policy;
-        sbinfo->policy_nodes = policy_nodes;
+        sbinfo->free_blocks = sbinfo->max_blocks;
+        sbinfo->free_inodes = sbinfo->max_inodes;
 
-        sb->s_fs_info = sbinfo;
         sb->s_maxbytes = SHMEM_MAX_BYTES;
         sb->s_blocksize = PAGE_CACHE_SIZE;
         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
@@ -2280,11 +2347,11 @@ static int shmem_fill_super(struct super_block *sb,
         sb->s_flags |= MS_POSIXACL;
 #endif
 
-        inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
+        inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
         if (!inode)
                 goto failed;
-        inode->i_uid = uid;
-        inode->i_gid = gid;
+        inode->i_uid = sbinfo->uid;
+        inode->i_gid = sbinfo->gid;
         root = d_alloc_root(inode);
         if (!root)
                 goto failed_iput;
@@ -2420,6 +2487,7 @@ static const struct super_operations shmem_ops = {
 #ifdef CONFIG_TMPFS
         .statfs         = shmem_statfs,
         .remount_fs     = shmem_remount_fs,
+        .show_options   = shmem_show_options,
 #endif
         .delete_inode   = shmem_delete_inode,
         .drop_inode     = generic_delete_inode,