[PATCH] hugetlbfs: mount options and permissions

From: "Seth, Rohit" <rohit.seth@intel.com>

This patch enables system administrators to more flexibly assign read/write
permissions to files in hugetlbfs.  Mount options are added which will
specify the uid, gid and mode of the filesystem's root directory.

This patch also enables super users to do chown/chgrp on files in hugetlbfs.

Also included in this patch is the support for uid, gid and mode command line
options for mount command for hugetlbfs.

The following mount options are added to hugetlbfs:

	uid=value gid=value mode=value

The values may be specified in hex (0xNNN), decimal or octal (0NNN).

Documentation/vm/hugetlbpage.txt

@@ -67,15 +67,22 @@ If the user applications are going to request hugepages using mmap system
 call, then it is required that system administrator mount a file system of
 type hugetlbfs:
 
-	mount none /mnt/huge -t hugetlbfs
+	mount none /mnt/huge -t hugetlbfs <uid=value> <gid=value> <mode=value>
 
 This command mounts a (pseudo) filesystem of type hugetlbfs on the directory
-/mnt/huge.  Any files created on /mnt/huge uses hugepages.  An example is
-given at the end of this document.
+/mnt/huge.  Any files created on /mnt/huge uses hugepages.  The uid and gid
+options sets the owner and group of the root of the file system.  By default
+the uid and gid of the current process are taken.  The mode option sets the
+mode of root of file system to value & 0777.  This value is given in octal.
+By default the value 0755 is picked.  An example is given at the end of this
+document.
 
 read and write system calls are not supported on files that reside on hugetlb
 file systems.
 
+A regular chown, chgrp and chmod commands (with right permissions) could be
+used to change the file attributes on hugetlbfs.
+
 Also, it is important to note that no such mount command is required if the
 applications are going to use only shmat/shmget system calls.  It is possible
 for same or different applications to use any combination of mmaps and shm*

fs/hugetlbfs/inode.c

@@ -48,9 +48,6 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 	loff_t len;
 	int ret;
 
-	if (!capable(CAP_IPC_LOCK))
-		return -EPERM;
-
 	if (vma->vm_start & ~HPAGE_MASK)
 		return -EINVAL;
 
@@ -231,6 +228,7 @@ static void hugetlbfs_forget_inode(struct inode *inode)
 	spin_unlock(&inode_lock);
 	if (inode->i_data.nrpages)
 		truncate_hugepages(&inode->i_data, 0);
+
 	clear_inode(inode);
 	destroy_inode(inode);
 }
@@ -317,7 +315,6 @@ static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
 	struct inode *inode = dentry->d_inode;
 	int error;
 	unsigned int ia_valid = attr->ia_valid;
-	unsigned long dn_mask;
 
 	BUG_ON(!inode);
 
@@ -335,26 +332,21 @@ static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
 		if (error)
 			goto out;
 		attr->ia_valid &= ~ATTR_SIZE;
-		error = inode_setattr(inode, attr);
 	}
-	if (error)
-		goto out;
-	dn_mask = setattr_mask(ia_valid);
-	if (dn_mask)
-		dnotify_parent(dentry, dn_mask);
+	error = inode_setattr(inode, attr);
 out:
 	return error;
 }
 
-static struct inode *hugetlbfs_get_inode(struct super_block *sb,
-					int mode, dev_t dev)
+static struct inode *hugetlbfs_get_inode(struct super_block *sb, uid_t uid, 
+					gid_t gid, int mode, dev_t dev)
 {
 	struct inode * inode = new_inode(sb);
 
 	if (inode) {
 		inode->i_mode = mode;
-		inode->i_uid = current->fsuid;
-		inode->i_gid = current->fsgid;
+		inode->i_uid = uid;
+		inode->i_gid = gid;
 		inode->i_blksize = PAGE_CACHE_SIZE;
 		inode->i_blocks = 0;
 		inode->i_rdev = NODEV;
@@ -391,7 +383,8 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb,
 static int hugetlbfs_mknod(struct inode *dir,
 			struct dentry *dentry, int mode, dev_t dev)
 {
-	struct inode * inode = hugetlbfs_get_inode(dir->i_sb, mode, dev);
+	struct inode * inode = hugetlbfs_get_inode(dir->i_sb, current->fsuid, 
+					current->fsgid, mode, dev);
 	int error = -ENOSPC;
 
 	if (inode) {
@@ -421,7 +414,8 @@ static int hugetlbfs_symlink(struct inode *dir,
 	struct inode *inode;
 	int error = -ENOSPC;
 
-	inode = hugetlbfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
+	inode = hugetlbfs_get_inode(dir->i_sb, current->fsuid,
+					current->fsgid, S_IFLNK|S_IRWXUGO, 0);
 	if (inode) {
 		int l = strlen(symname)+1;
 		error = page_symlink(inode, symname, l);
@@ -478,16 +472,68 @@ static struct super_operations hugetlbfs_ops = {
 };
 
 static int
-hugetlbfs_fill_super(struct super_block * sb, void * data, int silent)
+hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
+{
+	char *opt, *value;
+	int ret = 0;
+
+	if (!options)
+		goto out;
+	while ((opt = strsep(&options, ",")) != NULL) {
+		if (!*opt)
+			continue;
+
+		value = strchr(opt, '=');
+		if (!value || !*value) {
+			ret = -EINVAL;
+			goto out;
+		} else {
+			*value++ = '\0';
+		}
+
+		if (!strcmp(opt, "uid"))
+			pconfig->uid = simple_strtoul(value, &value, 0);
+		else if (!strcmp(opt, "gid"))
+			pconfig->gid = simple_strtoul(value, &value, 0);
+		else if (!strcmp(opt, "mode"))
+			pconfig->mode = simple_strtoul(value,&value,0) & 0777U;
+		else {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (*value) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+	return 0;
+out:
+	pconfig->uid = current->fsuid;
+	pconfig->gid = current->fsgid;
+	pconfig->mode = 0755;
+	return ret;
+}
+
+static int
+hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct inode * inode;
 	struct dentry * root;
+	int ret;
+	struct hugetlbfs_config config;
 
+	ret = hugetlbfs_parse_options(data, &config);
+	if (ret) {
+		printk("hugetlbfs: invalid mount options: %s.\n", data);
+		return ret;
+	}
 	sb->s_blocksize = PAGE_CACHE_SIZE;
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	sb->s_magic = HUGETLBFS_MAGIC;
 	sb->s_op = &hugetlbfs_ops;
-	inode = hugetlbfs_get_inode(sb, S_IFDIR | 0755, 0);
+	inode = hugetlbfs_get_inode(sb, config.uid, config.gid,
+					S_IFDIR | config.mode, 0);
 	if (!inode)
 		return -ENOMEM;
 
@@ -548,7 +594,8 @@ struct file *hugetlb_zero_setup(size_t size)
 		goto out_dentry;
 
 	error = -ENOSPC;
-	inode = hugetlbfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
+	inode = hugetlbfs_get_inode(root->d_sb, current->fsuid,
+				current->fsgid, S_IFREG | S_IRWXUGO, 0);
 	if (!inode)
 		goto out_file;
 

include/linux/hugetlb.h

@@ -72,6 +72,12 @@ static inline int is_vm_hugetlb_page(struct vm_area_struct *vma)
 #endif /* !CONFIG_HUGETLB_PAGE */
 
 #ifdef CONFIG_HUGETLBFS
+struct hugetlbfs_config {
+        uid_t   uid;
+        gid_t   gid;
+        umode_t mode;
+};
+
 extern struct file_operations hugetlbfs_file_operations;
 extern struct vm_operations_struct hugetlb_vm_ops;
 struct file *hugetlb_zero_setup(size_t);