hugetlbfs: use lib/parser, fix docs

[deliverable/linux.git] / fs / hugetlbfs / inode.c

/*
 * hugetlbpage-backed filesystem.  Based on ramfs.
 *
 * William Irwin, 2002
 *
 * Copyright (C) 2002 Linus Torvalds.
 */

#include <linux/module.h>
#include <linux/thread_info.h>
#include <asm/current.h>
#include <linux/sched.h>                /* remove ASAP */
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/kernel.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/capability.h>
#include <linux/ctype.h>
#include <linux/backing-dev.h>
#include <linux/hugetlb.h>
#include <linux/pagevec.h>
#include <linux/parser.h>
#include <linux/mman.h>
#include <linux/quotaops.h>
#include <linux/slab.h>
#include <linux/dnotify.h>
#include <linux/statfs.h>
#include <linux/security.h>

#include <asm/uaccess.h>

/* some random number */
#define HUGETLBFS_MAGIC 0x958458f6

static const struct super_operations hugetlbfs_ops;
static const struct address_space_operations hugetlbfs_aops;
const struct file_operations hugetlbfs_file_operations;
static const struct inode_operations hugetlbfs_dir_inode_operations;
static const struct inode_operations hugetlbfs_inode_operations;

static struct backing_dev_info hugetlbfs_backing_dev_info = {
        .ra_pages       = 0,    /* No readahead */
        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};

int sysctl_hugetlb_shm_group;

enum {
        Opt_size, Opt_nr_inodes,
        Opt_mode, Opt_uid, Opt_gid,
        Opt_err,
};

static match_table_t tokens = {
        {Opt_size,      "size=%s"},
        {Opt_nr_inodes, "nr_inodes=%s"},
        {Opt_mode,      "mode=%o"},
        {Opt_uid,       "uid=%u"},
        {Opt_gid,       "gid=%u"},
        {Opt_err,       NULL},
};

static void huge_pagevec_release(struct pagevec *pvec)
{
        int i;

        for (i = 0; i < pagevec_count(pvec); ++i)
                put_page(pvec->pages[i]);

        pagevec_reinit(pvec);
}

static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        loff_t len, vma_len;
        int ret;

        /*
         * vma alignment has already been checked by prepare_hugepage_range.
         * If you add any error returns here, do so after setting VM_HUGETLB,
         * so is_vm_hugetlb_page tests below unmap_region go the right way
         * when do_mmap_pgoff unwinds (may be important on powerpc and ia64).
         */
        vma->vm_flags |= VM_HUGETLB | VM_RESERVED;
        vma->vm_ops = &hugetlb_vm_ops;

        vma_len = (loff_t)(vma->vm_end - vma->vm_start);

        mutex_lock(&inode->i_mutex);
        file_accessed(file);

        ret = -ENOMEM;
        len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

        if (vma->vm_flags & VM_MAYSHARE &&
            hugetlb_reserve_pages(inode, vma->vm_pgoff >> (HPAGE_SHIFT-PAGE_SHIFT),
                                  len >> HPAGE_SHIFT))
                goto out;

        ret = 0;
        hugetlb_prefault_arch_hook(vma->vm_mm);
        if (vma->vm_flags & VM_WRITE && inode->i_size < len)
                inode->i_size = len;
out:
        mutex_unlock(&inode->i_mutex);

        return ret;
}

/*
 * Called under down_write(mmap_sem).
 */

#ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
static unsigned long
hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
                unsigned long len, unsigned long pgoff, unsigned long flags)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long start_addr;

        if (len & ~HPAGE_MASK)
                return -EINVAL;
        if (len > TASK_SIZE)
                return -ENOMEM;

        if (flags & MAP_FIXED) {
                if (prepare_hugepage_range(addr, len, pgoff))
                        return -EINVAL;
                return addr;
        }

        if (addr) {
                addr = ALIGN(addr, HPAGE_SIZE);
                vma = find_vma(mm, addr);
                if (TASK_SIZE - len >= addr &&
                    (!vma || addr + len <= vma->vm_start))
                        return addr;
        }

        start_addr = mm->free_area_cache;

        if (len <= mm->cached_hole_size)
                start_addr = TASK_UNMAPPED_BASE;

full_search:
        addr = ALIGN(start_addr, HPAGE_SIZE);

        for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
                /* At this point:  (!vma || addr < vma->vm_end). */
                if (TASK_SIZE - len < addr) {
                        /*
                         * Start a new search - just in case we missed
                         * some holes.
                         */
                        if (start_addr != TASK_UNMAPPED_BASE) {
                                start_addr = TASK_UNMAPPED_BASE;
                                goto full_search;
                        }
                        return -ENOMEM;
                }

                if (!vma || addr + len <= vma->vm_start)
                        return addr;
                addr = ALIGN(vma->vm_end, HPAGE_SIZE);
        }
}
#endif

/*
 * Read a page. Again trivial. If it didn't already exist
 * in the page cache, it is zero-filled.
 */
static int hugetlbfs_readpage(struct file *file, struct page * page)
{
        unlock_page(page);
        return -EINVAL;
}

static int hugetlbfs_prepare_write(struct file *file,
                        struct page *page, unsigned offset, unsigned to)
{
        return -EINVAL;
}

static int hugetlbfs_commit_write(struct file *file,
                        struct page *page, unsigned offset, unsigned to)
{
        return -EINVAL;
}

static void truncate_huge_page(struct page *page)
{
        cancel_dirty_page(page, /* No IO accounting for huge pages? */0);
        ClearPageUptodate(page);
        remove_from_page_cache(page);
        put_page(page);
}

static void truncate_hugepages(struct inode *inode, loff_t lstart)
{
        struct address_space *mapping = &inode->i_data;
        const pgoff_t start = lstart >> HPAGE_SHIFT;
        struct pagevec pvec;
        pgoff_t next;
        int i, freed = 0;

        pagevec_init(&pvec, 0);
        next = start;
        while (1) {
                if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
                        if (next == start)
                                break;
                        next = start;
                        continue;
                }

                for (i = 0; i < pagevec_count(&pvec); ++i) {
                        struct page *page = pvec.pages[i];

                        lock_page(page);
                        if (page->index > next)
                                next = page->index;
                        ++next;
                        truncate_huge_page(page);
                        unlock_page(page);
                        hugetlb_put_quota(mapping);
                        freed++;
                }
                huge_pagevec_release(&pvec);
        }
        BUG_ON(!lstart && mapping->nrpages);
        hugetlb_unreserve_pages(inode, start, freed);
}

static void hugetlbfs_delete_inode(struct inode *inode)
{
        truncate_hugepages(inode, 0);
        clear_inode(inode);
}

static void hugetlbfs_forget_inode(struct inode *inode) __releases(inode_lock)
{
        struct super_block *sb = inode->i_sb;

        if (!hlist_unhashed(&inode->i_hash)) {
                if (!(inode->i_state & (I_DIRTY|I_LOCK)))
                        list_move(&inode->i_list, &inode_unused);
                inodes_stat.nr_unused++;
                if (!sb || (sb->s_flags & MS_ACTIVE)) {
                        spin_unlock(&inode_lock);
                        return;
                }
                inode->i_state |= I_WILL_FREE;
                spin_unlock(&inode_lock);
                /*
                 * write_inode_now is a noop as we set BDI_CAP_NO_WRITEBACK
                 * in our backing_dev_info.
                 */
                write_inode_now(inode, 1);
                spin_lock(&inode_lock);
                inode->i_state &= ~I_WILL_FREE;
                inodes_stat.nr_unused--;
                hlist_del_init(&inode->i_hash);
        }
        list_del_init(&inode->i_list);
        list_del_init(&inode->i_sb_list);
        inode->i_state |= I_FREEING;
        inodes_stat.nr_inodes--;
        spin_unlock(&inode_lock);
        truncate_hugepages(inode, 0);
        clear_inode(inode);
        destroy_inode(inode);
}

static void hugetlbfs_drop_inode(struct inode *inode)
{
        if (!inode->i_nlink)
                generic_delete_inode(inode);
        else
                hugetlbfs_forget_inode(inode);
}

static inline void
hugetlb_vmtruncate_list(struct prio_tree_root *root, pgoff_t pgoff)
{
        struct vm_area_struct *vma;
        struct prio_tree_iter iter;

        vma_prio_tree_foreach(vma, &iter, root, pgoff, ULONG_MAX) {
                unsigned long v_offset;

                /*
                 * Can the expression below overflow on 32-bit arches?
                 * No, because the prio_tree returns us only those vmas
                 * which overlap the truncated area starting at pgoff,
                 * and no vma on a 32-bit arch can span beyond the 4GB.
                 */
                if (vma->vm_pgoff < pgoff)
                        v_offset = (pgoff - vma->vm_pgoff) << PAGE_SHIFT;
                else
                        v_offset = 0;

                __unmap_hugepage_range(vma,
                                vma->vm_start + v_offset, vma->vm_end);
        }
}

/*
 * Expanding truncates are not allowed.
 */
static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
{
        pgoff_t pgoff;
        struct address_space *mapping = inode->i_mapping;

        if (offset > inode->i_size)
                return -EINVAL;

        BUG_ON(offset & ~HPAGE_MASK);
        pgoff = offset >> PAGE_SHIFT;

        inode->i_size = offset;
        spin_lock(&mapping->i_mmap_lock);
        if (!prio_tree_empty(&mapping->i_mmap))
                hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
        spin_unlock(&mapping->i_mmap_lock);
        truncate_hugepages(inode, offset);
        return 0;
}

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;

        BUG_ON(!inode);

        error = inode_change_ok(inode, attr);
        if (error)
                goto out;

        if (ia_valid & ATTR_SIZE) {
                error = -EINVAL;
                if (!(attr->ia_size & ~HPAGE_MASK))
                        error = hugetlb_vmtruncate(inode, attr->ia_size);
                if (error)
                        goto out;
                attr->ia_valid &= ~ATTR_SIZE;
        }
        error = inode_setattr(inode, attr);
out:
        return error;
}

static struct inode *hugetlbfs_get_inode(struct super_block *sb, uid_t uid, 
                                        gid_t gid, int mode, dev_t dev)
{
        struct inode *inode;

        inode = new_inode(sb);
        if (inode) {
                struct hugetlbfs_inode_info *info;
                inode->i_mode = mode;
                inode->i_uid = uid;
                inode->i_gid = gid;
                inode->i_blocks = 0;
                inode->i_mapping->a_ops = &hugetlbfs_aops;
                inode->i_mapping->backing_dev_info =&hugetlbfs_backing_dev_info;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
                INIT_LIST_HEAD(&inode->i_mapping->private_list);
                info = HUGETLBFS_I(inode);
                mpol_shared_policy_init(&info->policy, MPOL_DEFAULT, NULL);
                switch (mode & S_IFMT) {
                default:
                        init_special_inode(inode, mode, dev);
                        break;
                case S_IFREG:
                        inode->i_op = &hugetlbfs_inode_operations;
                        inode->i_fop = &hugetlbfs_file_operations;
                        break;
                case S_IFDIR:
                        inode->i_op = &hugetlbfs_dir_inode_operations;
                        inode->i_fop = &simple_dir_operations;

                        /* directory inodes start off with i_nlink == 2 (for "." entry) */
                        inc_nlink(inode);
                        break;
                case S_IFLNK:
                        inode->i_op = &page_symlink_inode_operations;
                        break;
                }
        }
        return inode;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
static int hugetlbfs_mknod(struct inode *dir,
                        struct dentry *dentry, int mode, dev_t dev)
{
        struct inode *inode;
        int error = -ENOSPC;
        gid_t gid;

        if (dir->i_mode & S_ISGID) {
                gid = dir->i_gid;
                if (S_ISDIR(mode))
                        mode |= S_ISGID;
        } else {
                gid = current->fsgid;
        }
        inode = hugetlbfs_get_inode(dir->i_sb, current->fsuid, gid, mode, dev);
        if (inode) {
                dir->i_ctime = dir->i_mtime = CURRENT_TIME;
                d_instantiate(dentry, inode);
                dget(dentry);   /* Extra count - pin the dentry in core */
                error = 0;
        }
        return error;
}

static int hugetlbfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        int retval = hugetlbfs_mknod(dir, dentry, mode | S_IFDIR, 0);
        if (!retval)
                inc_nlink(dir);
        return retval;
}

static int hugetlbfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
{
        return hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0);
}

static int hugetlbfs_symlink(struct inode *dir,
                        struct dentry *dentry, const char *symname)
{
        struct inode *inode;
        int error = -ENOSPC;
        gid_t gid;

        if (dir->i_mode & S_ISGID)
                gid = dir->i_gid;
        else
                gid = current->fsgid;

        inode = hugetlbfs_get_inode(dir->i_sb, current->fsuid,
                                        gid, S_IFLNK|S_IRWXUGO, 0);
        if (inode) {
                int l = strlen(symname)+1;
                error = page_symlink(inode, symname, l);
                if (!error) {
                        d_instantiate(dentry, inode);
                        dget(dentry);
                } else
                        iput(inode);
        }
        dir->i_ctime = dir->i_mtime = CURRENT_TIME;

        return error;
}

/*
 * mark the head page dirty
 */
static int hugetlbfs_set_page_dirty(struct page *page)
{
        struct page *head = compound_head(page);

        SetPageDirty(head);
        return 0;
}

static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(dentry->d_sb);

        buf->f_type = HUGETLBFS_MAGIC;
        buf->f_bsize = HPAGE_SIZE;
        if (sbinfo) {
                spin_lock(&sbinfo->stat_lock);
                /* If no limits set, just report 0 for max/free/used
                 * blocks, like simple_statfs() */
                if (sbinfo->max_blocks >= 0) {
                        buf->f_blocks = sbinfo->max_blocks;
                        buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
                        buf->f_files = sbinfo->max_inodes;
                        buf->f_ffree = sbinfo->free_inodes;
                }
                spin_unlock(&sbinfo->stat_lock);
        }
        buf->f_namelen = NAME_MAX;
        return 0;
}

static void hugetlbfs_put_super(struct super_block *sb)
{
        struct hugetlbfs_sb_info *sbi = HUGETLBFS_SB(sb);

        if (sbi) {
                sb->s_fs_info = NULL;
                kfree(sbi);
        }
}

static inline int hugetlbfs_dec_free_inodes(struct hugetlbfs_sb_info *sbinfo)
{
        if (sbinfo->free_inodes >= 0) {
                spin_lock(&sbinfo->stat_lock);
                if (unlikely(!sbinfo->free_inodes)) {
                        spin_unlock(&sbinfo->stat_lock);
                        return 0;
                }
                sbinfo->free_inodes--;
                spin_unlock(&sbinfo->stat_lock);
        }

        return 1;
}

static void hugetlbfs_inc_free_inodes(struct hugetlbfs_sb_info *sbinfo)
{
        if (sbinfo->free_inodes >= 0) {
                spin_lock(&sbinfo->stat_lock);
                sbinfo->free_inodes++;
                spin_unlock(&sbinfo->stat_lock);
        }
}


static struct kmem_cache *hugetlbfs_inode_cachep;

static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
{
        struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(sb);
        struct hugetlbfs_inode_info *p;

        if (unlikely(!hugetlbfs_dec_free_inodes(sbinfo)))
                return NULL;
        p = kmem_cache_alloc(hugetlbfs_inode_cachep, GFP_KERNEL);
        if (unlikely(!p)) {
                hugetlbfs_inc_free_inodes(sbinfo);
                return NULL;
        }
        return &p->vfs_inode;
}

static void hugetlbfs_destroy_inode(struct inode *inode)
{
        hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
        mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
        kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
}

static const struct address_space_operations hugetlbfs_aops = {
        .readpage       = hugetlbfs_readpage,
        .prepare_write  = hugetlbfs_prepare_write,
        .commit_write   = hugetlbfs_commit_write,
        .set_page_dirty = hugetlbfs_set_page_dirty,
};


static void init_once(void *foo, struct kmem_cache *cachep, unsigned long flags)
{
        struct hugetlbfs_inode_info *ei = (struct hugetlbfs_inode_info *)foo;

        inode_init_once(&ei->vfs_inode);
}

const struct file_operations hugetlbfs_file_operations = {
        .mmap                   = hugetlbfs_file_mmap,
        .fsync                  = simple_sync_file,
        .get_unmapped_area      = hugetlb_get_unmapped_area,
};

static const struct inode_operations hugetlbfs_dir_inode_operations = {
        .create         = hugetlbfs_create,
        .lookup         = simple_lookup,
        .link           = simple_link,
        .unlink         = simple_unlink,
        .symlink        = hugetlbfs_symlink,
        .mkdir          = hugetlbfs_mkdir,
        .rmdir          = simple_rmdir,
        .mknod          = hugetlbfs_mknod,
        .rename         = simple_rename,
        .setattr        = hugetlbfs_setattr,
};

static const struct inode_operations hugetlbfs_inode_operations = {
        .setattr        = hugetlbfs_setattr,
};

static const struct super_operations hugetlbfs_ops = {
        .alloc_inode    = hugetlbfs_alloc_inode,
        .destroy_inode  = hugetlbfs_destroy_inode,
        .statfs         = hugetlbfs_statfs,
        .delete_inode   = hugetlbfs_delete_inode,
        .drop_inode     = hugetlbfs_drop_inode,
        .put_super      = hugetlbfs_put_super,
};

static int
hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
{
        char *p, *rest;
        substring_t args[MAX_OPT_ARGS];
        int option;

        if (!options)
                return 0;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_uid:
                        if (match_int(&args[0], &option))
                                goto bad_val;
                        pconfig->uid = option;
                        break;

                case Opt_gid:
                        if (match_int(&args[0], &option))
                                goto bad_val;
                        pconfig->gid = option;
                        break;

                case Opt_mode:
                        if (match_octal(&args[0], &option))
                                goto bad_val;
                        pconfig->mode = option & 0777U;
                        break;

                case Opt_size: {
                        unsigned long long size;
                        /* memparse() will accept a K/M/G without a digit */
                        if (!isdigit(*args[0].from))
                                goto bad_val;
                        size = memparse(args[0].from, &rest);
                        if (*rest == '%') {
                                size <<= HPAGE_SHIFT;
                                size *= max_huge_pages;
                                do_div(size, 100);
                        }
                        pconfig->nr_blocks = (size >> HPAGE_SHIFT);
                        break;
                }

                case Opt_nr_inodes:
                        /* memparse() will accept a K/M/G without a digit */
                        if (!isdigit(*args[0].from))
                                goto bad_val;
                        pconfig->nr_inodes = memparse(args[0].from, &rest);
                        break;

                default:
                        printk(KERN_ERR "hugetlbfs: Bad mount option: %s\n", p);
                        return 1;
                        break;
                }
        }
        return 0;

bad_val:
        printk(KERN_ERR "hugetlbfs: Bad value '%s' for mount option '%s'\n",
               args[0].from, p);
        return 1;
}

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;
        struct hugetlbfs_sb_info *sbinfo;

        config.nr_blocks = -1; /* No limit on size by default */
        config.nr_inodes = -1; /* No limit on number of inodes by default */
        config.uid = current->fsuid;
        config.gid = current->fsgid;
        config.mode = 0755;
        ret = hugetlbfs_parse_options(data, &config);

        if (ret)
                return ret;

        sbinfo = kmalloc(sizeof(struct hugetlbfs_sb_info), GFP_KERNEL);
        if (!sbinfo)
                return -ENOMEM;
        sb->s_fs_info = sbinfo;
        spin_lock_init(&sbinfo->stat_lock);
        sbinfo->max_blocks = config.nr_blocks;
        sbinfo->free_blocks = config.nr_blocks;
        sbinfo->max_inodes = config.nr_inodes;
        sbinfo->free_inodes = config.nr_inodes;
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_blocksize = HPAGE_SIZE;
        sb->s_blocksize_bits = HPAGE_SHIFT;
        sb->s_magic = HUGETLBFS_MAGIC;
        sb->s_op = &hugetlbfs_ops;
        sb->s_time_gran = 1;
        inode = hugetlbfs_get_inode(sb, config.uid, config.gid,
                                        S_IFDIR | config.mode, 0);
        if (!inode)
                goto out_free;

        root = d_alloc_root(inode);
        if (!root) {
                iput(inode);
                goto out_free;
        }
        sb->s_root = root;
        return 0;
out_free:
        kfree(sbinfo);
        return -ENOMEM;
}

int hugetlb_get_quota(struct address_space *mapping)
{
        int ret = 0;
        struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(mapping->host->i_sb);

        if (sbinfo->free_blocks > -1) {
                spin_lock(&sbinfo->stat_lock);
                if (sbinfo->free_blocks > 0)
                        sbinfo->free_blocks--;
                else
                        ret = -ENOMEM;
                spin_unlock(&sbinfo->stat_lock);
        }

        return ret;
}

void hugetlb_put_quota(struct address_space *mapping)
{
        struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(mapping->host->i_sb);

        if (sbinfo->free_blocks > -1) {
                spin_lock(&sbinfo->stat_lock);
                sbinfo->free_blocks++;
                spin_unlock(&sbinfo->stat_lock);
        }
}

static int hugetlbfs_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
        return get_sb_nodev(fs_type, flags, data, hugetlbfs_fill_super, mnt);
}

static struct file_system_type hugetlbfs_fs_type = {
        .name           = "hugetlbfs",
        .get_sb         = hugetlbfs_get_sb,
        .kill_sb        = kill_litter_super,
};

static struct vfsmount *hugetlbfs_vfsmount;

static int can_do_hugetlb_shm(void)
{
        return likely(capable(CAP_IPC_LOCK) ||
                        in_group_p(sysctl_hugetlb_shm_group) ||
                        can_do_mlock());
}

struct file *hugetlb_file_setup(const char *name, size_t size)
{
        int error = -ENOMEM;
        struct file *file;
        struct inode *inode;
        struct dentry *dentry, *root;
        struct qstr quick_string;

        if (!hugetlbfs_vfsmount)
                return ERR_PTR(-ENOENT);

        if (!can_do_hugetlb_shm())
                return ERR_PTR(-EPERM);

        if (!user_shm_lock(size, current->user))
                return ERR_PTR(-ENOMEM);

        root = hugetlbfs_vfsmount->mnt_root;
        quick_string.name = name;
        quick_string.len = strlen(quick_string.name);
        quick_string.hash = 0;
        dentry = d_alloc(root, &quick_string);
        if (!dentry)
                goto out_shm_unlock;

        error = -ENFILE;
        file = get_empty_filp();
        if (!file)
                goto out_dentry;

        error = -ENOSPC;
        inode = hugetlbfs_get_inode(root->d_sb, current->fsuid,
                                current->fsgid, S_IFREG | S_IRWXUGO, 0);
        if (!inode)
                goto out_file;

        error = -ENOMEM;
        if (hugetlb_reserve_pages(inode, 0, size >> HPAGE_SHIFT))
                goto out_inode;

        d_instantiate(dentry, inode);
        inode->i_size = size;
        inode->i_nlink = 0;
        file->f_path.mnt = mntget(hugetlbfs_vfsmount);
        file->f_path.dentry = dentry;
        file->f_mapping = inode->i_mapping;
        file->f_op = &hugetlbfs_file_operations;
        file->f_mode = FMODE_WRITE | FMODE_READ;
        return file;

out_inode:
        iput(inode);
out_file:
        put_filp(file);
out_dentry:
        dput(dentry);
out_shm_unlock:
        user_shm_unlock(size, current->user);
        return ERR_PTR(error);
}

static int __init init_hugetlbfs_fs(void)
{
        int error;
        struct vfsmount *vfsmount;

        hugetlbfs_inode_cachep = kmem_cache_create("hugetlbfs_inode_cache",
                                        sizeof(struct hugetlbfs_inode_info),
                                        0, 0, init_once, NULL);
        if (hugetlbfs_inode_cachep == NULL)
                return -ENOMEM;

        error = register_filesystem(&hugetlbfs_fs_type);
        if (error)
                goto out;

        vfsmount = kern_mount(&hugetlbfs_fs_type);

        if (!IS_ERR(vfsmount)) {
                hugetlbfs_vfsmount = vfsmount;
                return 0;
        }

        error = PTR_ERR(vfsmount);

 out:
        if (error)
                kmem_cache_destroy(hugetlbfs_inode_cachep);
        return error;
}

static void __exit exit_hugetlbfs_fs(void)
{
        kmem_cache_destroy(hugetlbfs_inode_cachep);
        unregister_filesystem(&hugetlbfs_fs_type);
}

module_init(init_hugetlbfs_fs)
module_exit(exit_hugetlbfs_fs)

MODULE_LICENSE("GPL");