hugetlbfs: Implement show_options

Implement the show_options superblock op for hugetlbfs as part of a bid to
get rid of s_options and generic_show_options() to make it easier to
implement a context-based mount where the mount options can be passed
individually over a file descriptor.

Note that the uid and gid should possibly be displayed relative to the
viewer's user namespace.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 59 insertions, 14 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index d44f5456eb9b..99b3b9836575 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -46,13 +46,13 @@ static const struct inode_operations hugetlbfs_dir_inode_operations;
 static const struct inode_operations hugetlbfs_inode_operations;
 
 struct hugetlbfs_config {
-        kuid_t   uid;
-        kgid_t   gid;
-        umode_t mode;
-        long    max_hpages;
-        long    nr_inodes;
-        struct hstate *hstate;
-        long    min_hpages;
+        struct hstate           *hstate;
+        long                    max_hpages;
+        long                    nr_inodes;
+        long                    min_hpages;
+        kuid_t                  uid;
+        kgid_t                  gid;
+        umode_t                 mode;
 };
 
 struct hugetlbfs_inode_info {
@@ -851,6 +851,46 @@ static int hugetlbfs_migrate_page(struct address_space *mapping,
         return MIGRATEPAGE_SUCCESS;
 }
 
+/*
+ * Display the mount options in /proc/mounts.
+ */
+static int hugetlbfs_show_options(struct seq_file *m, struct dentry *root)
+{
+        struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(root->d_sb);
+        struct hugepage_subpool *spool = sbinfo->spool;
+        unsigned long hpage_size = huge_page_size(sbinfo->hstate);
+        unsigned hpage_shift = huge_page_shift(sbinfo->hstate);
+        char mod;
+
+        if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
+                seq_printf(m, ",uid=%u",
+                           from_kuid_munged(&init_user_ns, sbinfo->uid));
+        if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
+                seq_printf(m, ",gid=%u",
+                           from_kgid_munged(&init_user_ns, sbinfo->gid));
+        if (sbinfo->mode != 0755)
+                seq_printf(m, ",mode=%o", sbinfo->mode);
+        if (sbinfo->max_inodes != -1)
+                seq_printf(m, ",nr_inodes=%lu", sbinfo->max_inodes);
+
+        hpage_size /= 1024;
+        mod = 'K';
+        if (hpage_size >= 1024) {
+                hpage_size /= 1024;
+                mod = 'M';
+        }
+        seq_printf(m, ",pagesize=%lu%c", hpage_size, mod);
+        if (spool) {
+                if (spool->max_hpages != -1)
+                        seq_printf(m, ",size=%llu",
+                                   (unsigned long long)spool->max_hpages << hpage_shift);
+                if (spool->min_hpages != -1)
+                        seq_printf(m, ",min_size=%llu",
+                                   (unsigned long long)spool->min_hpages << hpage_shift);
+        }
+        return 0;
+}
+
 static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
         struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(dentry->d_sb);
@@ -1008,19 +1048,19 @@ static const struct super_operations hugetlbfs_ops = {
         .evict_inode    = hugetlbfs_evict_inode,
         .statfs         = hugetlbfs_statfs,
         .put_super      = hugetlbfs_put_super,
-        .show_options   = generic_show_options,
+        .show_options   = hugetlbfs_show_options,
 };
 
-enum { NO_SIZE, SIZE_STD, SIZE_PERCENT };
+enum hugetlbfs_size_type { NO_SIZE, SIZE_STD, SIZE_PERCENT };
 
 /*
  * Convert size option passed from command line to number of huge pages
  * in the pool specified by hstate.  Size option could be in bytes
  * (val_type == SIZE_STD) or percentage of the pool (val_type == SIZE_PERCENT).
  */
-static long long
+static long
 hugetlbfs_size_to_hpages(struct hstate *h, unsigned long long size_opt,
-                                                                int val_type)
+                         enum hugetlbfs_size_type val_type)
 {
         if (val_type == NO_SIZE)
                 return -1;
@@ -1042,7 +1082,7 @@ hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
         substring_t args[MAX_OPT_ARGS];
         int option;
         unsigned long long max_size_opt = 0, min_size_opt = 0;
-        int max_val_type = NO_SIZE, min_val_type = NO_SIZE;
+        enum hugetlbfs_size_type max_val_type = NO_SIZE, min_val_type = NO_SIZE;
 
         if (!options)
                 return 0;
@@ -1156,8 +1196,6 @@ hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
         struct hugetlbfs_config config;
         struct hugetlbfs_sb_info *sbinfo;
 
-        save_mount_options(sb, data);
-
         config.max_hpages = -1; /* No limit on size by default */
         config.nr_inodes = -1; /* No limit on number of inodes by default */
         config.uid = current_fsuid();
@@ -1178,6 +1216,10 @@ hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
         sbinfo->max_inodes = config.nr_inodes;
         sbinfo->free_inodes = config.nr_inodes;
         sbinfo->spool = NULL;
+        sbinfo->uid = config.uid;
+        sbinfo->gid = config.gid;
+        sbinfo->mode = config.mode;
+
         /*
          * Allocate and initialize subpool if maximum or minimum size is
          * specified.  Any needed reservations (for minimim size) are taken
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index b857fc8cc2ec..3b6eeaad2f77 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -262,6 +262,9 @@ struct hugetlbfs_sb_info {
         spinlock_t      stat_lock;
         struct hstate *hstate;
         struct hugepage_subpool *spool;
+        kuid_t  uid;
+        kgid_t  gid;
+        umode_t mode;
 };
 
 static inline struct hugetlbfs_sb_info *HUGETLBFS_SB(struct super_block *sb)