inode.c

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/*
 * 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/slab.h>
#include <linux/dnotify.h>
#include <linux/statfs.h>
#include <linux/security.h>
#include <linux/magic.h>
#include <linux/migrate.h>

#include <asm/uaccess.h>

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;

struct hugetlbfs_config {
    kuid_t   uid;
    kgid_t   gid;
    umode_t mode;
    long    nr_blocks;
    long    nr_inodes;
    struct hstate *hstate;
};

struct hugetlbfs_inode_info {
    struct shared_policy policy;
    struct inode vfs_inode;
};

static inline struct hugetlbfs_inode_info *HUGETLBFS_I(struct inode *inode)
{
    return container_of(inode, struct hugetlbfs_inode_info, vfs_inode);
}

static struct backing_dev_info hugetlbfs_backing_dev_info = {
    .name       = "hugetlbfs",
    .ra_pages   = 0,    /* No readahead */
    .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};

int sysctl_hugetlb_shm_group;

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

static const 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_pagesize,  "pagesize=%s"},
    {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;
    struct hstate *h = hstate_file(file);

    /*
     * vma address alignment (but not the pgoff 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_DONTEXPAND | VM_DONTDUMP;
    vma->vm_ops = &hugetlb_vm_ops;

    if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
        return -EINVAL;

    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 (hugetlb_reserve_pages(inode,
                vma->vm_pgoff >> huge_page_order(h),
                len >> huge_page_shift(h), vma,
                vma->vm_flags))
        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;
    struct hstate *h = hstate_file(file);

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

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

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

    if (len > mm->cached_hole_size)
        start_addr = mm->free_area_cache;
    else {
        start_addr = TASK_UNMAPPED_BASE;
        mm->cached_hole_size = 0;
    }

full_search:
    addr = ALIGN(start_addr, huge_page_size(h));

    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;
                mm->cached_hole_size = 0;
                goto full_search;
            }
            return -ENOMEM;
        }

        if (!vma || addr + len <= vma->vm_start) {
            mm->free_area_cache = addr + len;
            return addr;
        }
        if (addr + mm->cached_hole_size < vma->vm_start)
            mm->cached_hole_size = vma->vm_start - addr;
        addr = ALIGN(vma->vm_end, huge_page_size(h));
    }
}
#endif

static int
hugetlbfs_read_actor(struct page *page, unsigned long offset,
            char __user *buf, unsigned long count,
            unsigned long size)
{
    char *kaddr;
    unsigned long left, copied = 0;
    int i, chunksize;

    if (size > count)
        size = count;

    /* Find which 4k chunk and offset with in that chunk */
    i = offset >> PAGE_CACHE_SHIFT;
    offset = offset & ~PAGE_CACHE_MASK;

    while (size) {
        chunksize = PAGE_CACHE_SIZE;
        if (offset)
            chunksize -= offset;
        if (chunksize > size)
            chunksize = size;
        kaddr = kmap(&page[i]);
        left = __copy_to_user(buf, kaddr + offset, chunksize);
        kunmap(&page[i]);
        if (left) {
            copied += (chunksize - left);
            break;
        }
        offset = 0;
        size -= chunksize;
        buf += chunksize;
        copied += chunksize;
        i++;
    }
    return copied ? copied : -EFAULT;
}

/*
 * Support for read() - Find the page attached to f_mapping and copy out the
 * data. Its *very* similar to do_generic_mapping_read(), we can't use that
 * since it has PAGE_CACHE_SIZE assumptions.
 */
static ssize_t hugetlbfs_read(struct file *filp, char __user *buf,
                  size_t len, loff_t *ppos)
{
    struct hstate *h = hstate_file(filp);
    struct address_space *mapping = filp->f_mapping;
    struct inode *inode = mapping->host;
    unsigned long index = *ppos >> huge_page_shift(h);
    unsigned long offset = *ppos & ~huge_page_mask(h);
    unsigned long end_index;
    loff_t isize;
    ssize_t retval = 0;

    /* validate length */
    if (len == 0)
        goto out;

    for (;;) {
        struct page *page;
        unsigned long nr, ret;
        int ra;

        /* nr is the maximum number of bytes to copy from this page */
        nr = huge_page_size(h);
        isize = i_size_read(inode);
        if (!isize)
            goto out;
        end_index = (isize - 1) >> huge_page_shift(h);
        if (index >= end_index) {
            if (index > end_index)
                goto out;
            nr = ((isize - 1) & ~huge_page_mask(h)) + 1;
            if (nr <= offset)
                goto out;
        }
        nr = nr - offset;

        /* Find the page */
        page = find_lock_page(mapping, index);
        if (unlikely(page == NULL)) {
            /*
             * We have a HOLE, zero out the user-buffer for the
             * length of the hole or request.
             */
            ret = len < nr ? len : nr;
            if (clear_user(buf, ret))
                ra = -EFAULT;
            else
                ra = 0;
        } else {
            unlock_page(page);

            /*
             * We have the page, copy it to user space buffer.
             */
            ra = hugetlbfs_read_actor(page, offset, buf, len, nr);
            ret = ra;
            page_cache_release(page);
        }
        if (ra < 0) {
            if (retval == 0)
                retval = ra;
            goto out;
        }

        offset += ret;
        retval += ret;
        len -= ret;
        index += offset >> huge_page_shift(h);
        offset &= ~huge_page_mask(h);

        /* short read or no more work */
        if ((ret != nr) || (len == 0))
            break;
    }
out:
    *ppos = ((loff_t)index << huge_page_shift(h)) + offset;
    return retval;
}

static int hugetlbfs_write_begin(struct file *file,
            struct address_space *mapping,
            loff_t pos, unsigned len, unsigned flags,
            struct page **pagep, void **fsdata)
{
    return -EINVAL;
}

static int hugetlbfs_write_end(struct file *file, struct address_space *mapping,
            loff_t pos, unsigned len, unsigned copied,
            struct page *page, void *fsdata)
{
    BUG();
    return -EINVAL;
}

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

static void truncate_hugepages(struct inode *inode, loff_t lstart)
{
    struct hstate *h = hstate_inode(inode);
    struct address_space *mapping = &inode->i_data;
    const pgoff_t start = lstart >> huge_page_shift(h);
    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);
            freed++;
        }
        huge_pagevec_release(&pvec);
    }
    BUG_ON(!lstart && mapping->nrpages);
    hugetlb_unreserve_pages(inode, start, freed);
}

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

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

    vma_interval_tree_foreach(vma, root, pgoff, ULONG_MAX) {
        unsigned long v_offset;

        /*
         * Can the expression below overflow on 32-bit arches?
         * No, because the interval 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, NULL);
    }
}

static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
{
    pgoff_t pgoff;
    struct address_space *mapping = inode->i_mapping;
    struct hstate *h = hstate_inode(inode);

    BUG_ON(offset & ~huge_page_mask(h));
    pgoff = offset >> PAGE_SHIFT;

    i_size_write(inode, offset);
    mutex_lock(&mapping->i_mmap_mutex);
    if (!RB_EMPTY_ROOT(&mapping->i_mmap))
        hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
    mutex_unlock(&mapping->i_mmap_mutex);
    truncate_hugepages(inode, offset);
    return 0;
}

static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
{
    struct inode *inode = dentry->d_inode;
    struct hstate *h = hstate_inode(inode);
    int error;
    unsigned int ia_valid = attr->ia_valid;

    BUG_ON(!inode);

    error = inode_change_ok(inode, attr);
    if (error)
        return error;

    if (ia_valid & ATTR_SIZE) {
        error = -EINVAL;
        if (attr->ia_size & ~huge_page_mask(h))
            return -EINVAL;
        error = hugetlb_vmtruncate(inode, attr->ia_size);
        if (error)
            return error;
    }

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);
    return 0;
}

static struct inode *hugetlbfs_get_root(struct super_block *sb,
                    struct hugetlbfs_config *config)
{
    struct inode *inode;

    inode = new_inode(sb);
    if (inode) {
        struct hugetlbfs_inode_info *info;
        inode->i_ino = get_next_ino();
        inode->i_mode = S_IFDIR | config->mode;
        inode->i_uid = config->uid;
        inode->i_gid = config->gid;
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        info = HUGETLBFS_I(inode);
        mpol_shared_policy_init(&info->policy, NULL);
        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);
        lockdep_annotate_inode_mutex_key(inode);
    }
    return inode;
}

static struct inode *hugetlbfs_get_inode(struct super_block *sb,
                    struct inode *dir,
                    umode_t mode, dev_t dev)
{
    struct inode *inode;

    inode = new_inode(sb);
    if (inode) {
        struct hugetlbfs_inode_info *info;
        inode->i_ino = get_next_ino();
        inode_init_owner(inode, dir, mode);
        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);
        /*
         * The policy is initialized here even if we are creating a
         * private inode because initialization simply creates an
         * an empty rb tree and calls spin_lock_init(), later when we
         * call mpol_free_shared_policy() it will just return because
         * the rb tree will still be empty.
         */
        mpol_shared_policy_init(&info->policy, 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;
        }
        lockdep_annotate_inode_mutex_key(inode);
    }
    return inode;
}

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

    inode = hugetlbfs_get_inode(dir->i_sb, dir, 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, umode_t 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, umode_t mode, bool excl)
{
    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;

    inode = hugetlbfs_get_inode(dir->i_sb, dir, 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_migrate_page(struct address_space *mapping,
                struct page *newpage, struct page *page,
                enum migrate_mode mode)
{
    int rc;

    rc = migrate_huge_page_move_mapping(mapping, newpage, page);
    if (rc)
        return rc;
    migrate_page_copy(newpage, page);

    return 0;
}

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

    buf->f_type = HUGETLBFS_MAGIC;
    buf->f_bsize = huge_page_size(h);
    if (sbinfo) {
        spin_lock(&sbinfo->stat_lock);
        /* If no limits set, just report 0 for max/free/used
         * blocks, like simple_statfs() */
        if (sbinfo->spool) {
            long free_pages;

            spin_lock(&sbinfo->spool->lock);
            buf->f_blocks = sbinfo->spool->max_hpages;
            free_pages = sbinfo->spool->max_hpages
                - sbinfo->spool->used_hpages;
            buf->f_bavail = buf->f_bfree = free_pages;
            spin_unlock(&sbinfo->spool->lock);
            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;

        if (sbi->spool)
            hugepage_put_subpool(sbi->spool);

        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_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(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);
    call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
}

static const struct address_space_operations hugetlbfs_aops = {
    .write_begin    = hugetlbfs_write_begin,
    .write_end  = hugetlbfs_write_end,
    .set_page_dirty = hugetlbfs_set_page_dirty,
    .migratepage    = hugetlbfs_migrate_page,
};


static void init_once(void *foo)
{
    struct hugetlbfs_inode_info *ei = (struct hugetlbfs_inode_info *)foo;

    inode_init_once(&ei->vfs_inode);
}

const struct file_operations hugetlbfs_file_operations = {
    .read           = hugetlbfs_read,
    .mmap           = hugetlbfs_file_mmap,
    .fsync          = noop_fsync,
    .get_unmapped_area  = hugetlb_get_unmapped_area,
    .llseek     = default_llseek,
};

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,
    .evict_inode    = hugetlbfs_evict_inode,
    .statfs     = hugetlbfs_statfs,
    .put_super  = hugetlbfs_put_super,
    .show_options   = generic_show_options,
};

static int
hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
{
    char *p, *rest;
    substring_t args[MAX_OPT_ARGS];
    int option;
    unsigned long long size = 0;
    enum { NO_SIZE, SIZE_STD, SIZE_PERCENT } setsize = NO_SIZE;

    if (!options)
        return 0;

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

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

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

        case Opt_mode:
            if (match_octal(&args[0], &option))
                goto bad_val;
            pconfig->mode = option & 01777U;
            break;

        case Opt_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);
            setsize = SIZE_STD;
            if (*rest == '%')
                setsize = SIZE_PERCENT;
            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;

        case Opt_pagesize: {
            unsigned long ps;
            ps = memparse(args[0].from, &rest);
            pconfig->hstate = size_to_hstate(ps);
            if (!pconfig->hstate) {
                printk(KERN_ERR
                "hugetlbfs: Unsupported page size %lu MB\n",
                    ps >> 20);
                return -EINVAL;
            }
            break;
        }

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

    /* Do size after hstate is set up */
    if (setsize > NO_SIZE) {
        struct hstate *h = pconfig->hstate;
        if (setsize == SIZE_PERCENT) {
            size <<= huge_page_shift(h);
            size *= h->max_huge_pages;
            do_div(size, 100);
        }
        pconfig->nr_blocks = (size >> huge_page_shift(h));
    }

    return 0;

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

static int
hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
{
    int ret;
    struct hugetlbfs_config config;
    struct hugetlbfs_sb_info *sbinfo;

    save_mount_options(sb, data);

    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;
    config.hstate = &default_hstate;
    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;
    sbinfo->hstate = config.hstate;
    spin_lock_init(&sbinfo->stat_lock);
    sbinfo->max_inodes = config.nr_inodes;
    sbinfo->free_inodes = config.nr_inodes;
    sbinfo->spool = NULL;
    if (config.nr_blocks != -1) {
        sbinfo->spool = hugepage_new_subpool(config.nr_blocks);
        if (!sbinfo->spool)
            goto out_free;
    }
    sb->s_maxbytes = MAX_LFS_FILESIZE;
    sb->s_blocksize = huge_page_size(config.hstate);
    sb->s_blocksize_bits = huge_page_shift(config.hstate);
    sb->s_magic = HUGETLBFS_MAGIC;
    sb->s_op = &hugetlbfs_ops;
    sb->s_time_gran = 1;
    sb->s_root = d_make_root(hugetlbfs_get_root(sb, &config));
    if (!sb->s_root)
        goto out_free;
    return 0;
out_free:
    if (sbinfo->spool)
        kfree(sbinfo->spool);
    kfree(sbinfo);
    return -ENOMEM;
}

static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
{
    return mount_nodev(fs_type, flags, data, hugetlbfs_fill_super);
}

static struct file_system_type hugetlbfs_fs_type = {
    .name       = "hugetlbfs",
    .mount      = hugetlbfs_mount,
    .kill_sb    = kill_litter_super,
};

static struct vfsmount *hugetlbfs_vfsmount;

static int can_do_hugetlb_shm(void)
{
    kgid_t shm_group;
    shm_group = make_kgid(&init_user_ns, sysctl_hugetlb_shm_group);
    return capable(CAP_IPC_LOCK) || in_group_p(shm_group);
}

struct file *hugetlb_file_setup(const char *name, unsigned long addr,
                size_t size, vm_flags_t acctflag,
                struct user_struct **user, int creat_flags)
{
    int error = -ENOMEM;
    struct file *file;
    struct inode *inode;
    struct path path;
    struct dentry *root;
    struct qstr quick_string;
    struct hstate *hstate;
    unsigned long num_pages;

    *user = NULL;
    if (!hugetlbfs_vfsmount)
        return ERR_PTR(-ENOENT);

    if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
        *user = current_user();
        if (user_shm_lock(size, *user)) {
            task_lock(current);
            printk_once(KERN_WARNING
                "%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated\n",
                current->comm, current->pid);
            task_unlock(current);
        } else {
            *user = NULL;
            return ERR_PTR(-EPERM);
        }
    }

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

    path.mnt = mntget(hugetlbfs_vfsmount);
    error = -ENOSPC;
    inode = hugetlbfs_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0);
    if (!inode)
        goto out_dentry;

    hstate = hstate_inode(inode);
    size += addr & ~huge_page_mask(hstate);
    num_pages = ALIGN(size, huge_page_size(hstate)) >>
            huge_page_shift(hstate);
    error = -ENOMEM;
    if (hugetlb_reserve_pages(inode, 0, num_pages, NULL, acctflag))
        goto out_inode;

    d_instantiate(path.dentry, inode);
    inode->i_size = size;
    clear_nlink(inode);

    error = -ENFILE;
    file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
            &hugetlbfs_file_operations);
    if (!file)
        goto out_dentry; /* inode is already attached */

    return file;

out_inode:
    iput(inode);
out_dentry:
    path_put(&path);
out_shm_unlock:
    if (*user) {
        user_shm_unlock(size, *user);
        *user = NULL;
    }
    return ERR_PTR(error);
}

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

    error = bdi_init(&hugetlbfs_backing_dev_info);
    if (error)
        return error;

    error = -ENOMEM;
    hugetlbfs_inode_cachep = kmem_cache_create("hugetlbfs_inode_cache",
                    sizeof(struct hugetlbfs_inode_info),
                    0, 0, init_once);
    if (hugetlbfs_inode_cachep == NULL)
        goto out2;

    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:
    kmem_cache_destroy(hugetlbfs_inode_cachep);
 out2:
    bdi_destroy(&hugetlbfs_backing_dev_info);
    return error;
}

static void __exit exit_hugetlbfs_fs(void)
{
    /*
     * Make sure all delayed rcu free inodes are flushed before we
     * destroy cache.
     */
    rcu_barrier();
    kmem_cache_destroy(hugetlbfs_inode_cachep);
    kern_unmount(hugetlbfs_vfsmount);
    unregister_filesystem(&hugetlbfs_fs_type);
    bdi_destroy(&hugetlbfs_backing_dev_info);
}

module_init(init_hugetlbfs_fs)
module_exit(exit_hugetlbfs_fs)

MODULE_LICENSE("GPL");