/*
   * hugetlbpage-backed filesystem.  Based on ramfs.
   *

   * Nadia Yvette Chambers, 2002

   *
   * Copyright (C) 2002 Linus Torvalds.

   * License: GPL

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/thread_info.h>
  #include <asm/current.h>
  #include <linux/sched.h>		/* remove ASAP */

  #include <linux/falloc.h>

  #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 <linux/uio.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	max_hpages;

  	long	nr_inodes;
  	struct hstate *hstate;

  	long    min_hpages;

  };
  
  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);
  }

  int sysctl_hugetlb_shm_group;

  enum {
  	Opt_size, Opt_nr_inodes,
  	Opt_mode, Opt_uid, Opt_gid,

  	Opt_pagesize, Opt_min_size,

  	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_min_size,	"min_size=%s"},

  	{Opt_err,	NULL},
  };

  #ifdef CONFIG_NUMA
  static inline void hugetlb_set_vma_policy(struct vm_area_struct *vma,
  					struct inode *inode, pgoff_t index)
  {
  	vma->vm_policy = mpol_shared_policy_lookup(&HUGETLBFS_I(inode)->policy,
  							index);
  }
  
  static inline void hugetlb_drop_vma_policy(struct vm_area_struct *vma)
  {
  	mpol_cond_put(vma->vm_policy);
  }
  #else
  static inline void hugetlb_set_vma_policy(struct vm_area_struct *vma,
  					struct inode *inode, pgoff_t index)
  {
  }
  
  static inline void hugetlb_drop_vma_policy(struct vm_area_struct *vma)
  {
  }
  #endif

  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_inode(file);

  	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;

  	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);

  	inode_lock(inode);

  	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;

  	if (vma->vm_flags & VM_WRITE && inode->i_size < len)

  		inode->i_size = len;
  out:

  	inode_unlock(inode);

  
  	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;

  	struct hstate *h = hstate_file(file);

  	struct vm_unmapped_area_info info;

  	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;
  	}

  	info.flags = 0;
  	info.length = len;
  	info.low_limit = TASK_UNMAPPED_BASE;
  	info.high_limit = TASK_SIZE;
  	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
  	info.align_offset = 0;
  	return vm_unmapped_area(&info);

  }
  #endif

  static size_t

  hugetlbfs_read_actor(struct page *page, unsigned long offset,

  			struct iov_iter *to, unsigned long size)

  {

  	size_t copied = 0;

  	int i, chunksize;

  	/* Find which 4k chunk and offset with in that chunk */

  	i = offset >> PAGE_SHIFT;
  	offset = offset & ~PAGE_MASK;

  
  	while (size) {

  		size_t n;

  		chunksize = PAGE_SIZE;

  		if (offset)
  			chunksize -= offset;
  		if (chunksize > size)
  			chunksize = size;

  		n = copy_page_to_iter(&page[i], offset, chunksize, to);
  		copied += n;
  		if (n != chunksize)
  			return copied;

  		offset = 0;
  		size -= chunksize;

  		i++;
  	}

  	return copied;

  }
  
  /*
   * 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_SIZE assumptions.

   */

  static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)

  {

  	struct file *file = iocb->ki_filp;
  	struct hstate *h = hstate_file(file);
  	struct address_space *mapping = file->f_mapping;

  	struct inode *inode = mapping->host;

  	unsigned long index = iocb->ki_pos >> huge_page_shift(h);
  	unsigned long offset = iocb->ki_pos & ~huge_page_mask(h);

  	unsigned long end_index;
  	loff_t isize;
  	ssize_t retval = 0;

  	while (iov_iter_count(to)) {

  		struct page *page;

  		size_t nr, copied;

  
  		/* nr is the maximum number of bytes to copy from this page */

  		nr = huge_page_size(h);

  		isize = i_size_read(inode);
  		if (!isize)

  			break;

  		end_index = (isize - 1) >> huge_page_shift(h);

  		if (index > end_index)
  			break;
  		if (index == end_index) {

  			nr = ((isize - 1) & ~huge_page_mask(h)) + 1;

  			if (nr <= offset)

  				break;

  		}
  		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.
  			 */

  			copied = iov_iter_zero(nr, to);

  		} else {

  			unlock_page(page);

  			/*
  			 * We have the page, copy it to user space buffer.
  			 */

  			copied = hugetlbfs_read_actor(page, offset, to, nr);

  			put_page(page);

  		}

  		offset += copied;
  		retval += copied;
  		if (copied != nr && iov_iter_count(to)) {
  			if (!retval)
  				retval = -EFAULT;
  			break;

  		}

  		index += offset >> huge_page_shift(h);
  		offset &= ~huge_page_mask(h);

  	}

  	iocb->ki_pos = ((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 remove_huge_page(struct page *page)

  {

  	ClearPageDirty(page);

  	ClearPageUptodate(page);

  	delete_from_page_cache(page);

  }

  static void
  hugetlb_vmdelete_list(struct rb_root *root, pgoff_t start, pgoff_t end)
  {
  	struct vm_area_struct *vma;
  
  	/*
  	 * end == 0 indicates that the entire range after
  	 * start should be unmapped.
  	 */
  	vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
  		unsigned long v_offset;
  		unsigned long v_end;
  
  		/*
  		 * 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 < start)
  			v_offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
  		else
  			v_offset = 0;
  
  		if (!end)
  			v_end = vma->vm_end;
  		else {
  			v_end = ((end - vma->vm_pgoff) << PAGE_SHIFT)
  							+ vma->vm_start;
  			if (v_end > vma->vm_end)
  				v_end = vma->vm_end;
  		}
  
  		unmap_hugepage_range(vma, vma->vm_start + v_offset, v_end,
  									NULL);
  	}
  }

  
  /*
   * remove_inode_hugepages handles two distinct cases: truncation and hole
   * punch.  There are subtle differences in operation for each case.

   *

   * truncation is indicated by end of range being LLONG_MAX
   *	In this case, we first scan the range and release found pages.
   *	After releasing pages, hugetlb_unreserve_pages cleans up region/reserv

   *	maps and global counts.  Page faults can not race with truncation
   *	in this routine.  hugetlb_no_page() prevents page faults in the
   *	truncated range.  It checks i_size before allocation, and again after
   *	with the page table lock for the page held.  The same lock must be
   *	acquired to unmap a page.

   * hole punch is indicated if end is not LLONG_MAX
   *	In the hole punch case we scan the range and release found pages.
   *	Only when releasing a page is the associated region/reserv map
   *	deleted.  The region/reserv map for ranges without associated

   *	pages are not modified.  Page faults can race with hole punch.
   *	This is indicated if we find a mapped page.

   * Note: If the passed end of range value is beyond the end of file, but
   * not LLONG_MAX this routine still performs a hole punch operation.
   */
  static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
  				   loff_t lend)

  {

  	struct hstate *h = hstate_inode(inode);

  	struct address_space *mapping = &inode->i_data;

  	const pgoff_t start = lstart >> huge_page_shift(h);

  	const pgoff_t end = lend >> huge_page_shift(h);
  	struct vm_area_struct pseudo_vma;

  	struct pagevec pvec;
  	pgoff_t next;

  	int i, freed = 0;

  	long lookup_nr = PAGEVEC_SIZE;
  	bool truncate_op = (lend == LLONG_MAX);

  	memset(&pseudo_vma, 0, sizeof(struct vm_area_struct));
  	pseudo_vma.vm_flags = (VM_HUGETLB | VM_MAYSHARE | VM_SHARED);

  	pagevec_init(&pvec, 0);
  	next = start;

  	while (next < end) {
  		/*

  		 * Don't grab more pages than the number left in the range.

  		 */
  		if (end - next < lookup_nr)
  			lookup_nr = end - next;
  
  		/*

  		 * When no more pages are found, we are done.

  		 */

  		if (!pagevec_lookup(&pvec, mapping, next, lookup_nr))
  			break;

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

  			u32 hash;

  			/*
  			 * The page (index) could be beyond end.  This is
  			 * only possible in the punch hole case as end is
  			 * max page offset in the truncate case.
  			 */
  			next = page->index;
  			if (next >= end)
  				break;

  			hash = hugetlb_fault_mutex_hash(h, current->mm,
  							&pseudo_vma,
  							mapping, next, 0);
  			mutex_lock(&hugetlb_fault_mutex_table[hash]);

  			/*
  			 * If page is mapped, it was faulted in after being
  			 * unmapped in caller.  Unmap (again) now after taking
  			 * the fault mutex.  The mutex will prevent faults
  			 * until we finish removing the page.
  			 *
  			 * This race can only happen in the hole punch case.
  			 * Getting here in a truncate operation is a bug.
  			 */
  			if (unlikely(page_mapped(page))) {

  				BUG_ON(truncate_op);

  
  				i_mmap_lock_write(mapping);
  				hugetlb_vmdelete_list(&mapping->i_mmap,
  					next * pages_per_huge_page(h),
  					(next + 1) * pages_per_huge_page(h));
  				i_mmap_unlock_write(mapping);
  			}
  
  			lock_page(page);
  			/*
  			 * We must free the huge page and remove from page
  			 * cache (remove_huge_page) BEFORE removing the
  			 * region/reserve map (hugetlb_unreserve_pages).  In
  			 * rare out of memory conditions, removal of the

  			 * region/reserve map could fail. Correspondingly,
  			 * the subpool and global reserve usage count can need
  			 * to be adjusted.

  			 */

  			VM_BUG_ON(PagePrivate(page));

  			remove_huge_page(page);
  			freed++;
  			if (!truncate_op) {
  				if (unlikely(hugetlb_unreserve_pages(inode,
  							next, next + 1, 1)))

  					hugetlb_fix_reserve_counts(inode);

  			}

  			unlock_page(page);

  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);

  		}

  		++next;

  		huge_pagevec_release(&pvec);

  		cond_resched();

  	}

  
  	if (truncate_op)
  		(void)hugetlb_unreserve_pages(inode, start, LONG_MAX, freed);

  }

  static void hugetlbfs_evict_inode(struct inode *inode)

  {

  	struct resv_map *resv_map;

  	remove_inode_hugepages(inode, 0, LLONG_MAX);

  	resv_map = (struct resv_map *)inode->i_mapping->private_data;
  	/* root inode doesn't have the resv_map, so we should check it */
  	if (resv_map)
  		resv_map_release(&resv_map->refs);

  	clear_inode(inode);

  }

  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);

  	i_mmap_lock_write(mapping);

  	if (!RB_EMPTY_ROOT(&mapping->i_mmap))

  		hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);

  	i_mmap_unlock_write(mapping);

  	remove_inode_hugepages(inode, offset, LLONG_MAX);

  	return 0;
  }

  static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
  {
  	struct hstate *h = hstate_inode(inode);
  	loff_t hpage_size = huge_page_size(h);
  	loff_t hole_start, hole_end;
  
  	/*
  	 * For hole punch round up the beginning offset of the hole and
  	 * round down the end.
  	 */
  	hole_start = round_up(offset, hpage_size);
  	hole_end = round_down(offset + len, hpage_size);
  
  	if (hole_end > hole_start) {
  		struct address_space *mapping = inode->i_mapping;

  		inode_lock(inode);

  		i_mmap_lock_write(mapping);
  		if (!RB_EMPTY_ROOT(&mapping->i_mmap))
  			hugetlb_vmdelete_list(&mapping->i_mmap,
  						hole_start >> PAGE_SHIFT,
  						hole_end  >> PAGE_SHIFT);
  		i_mmap_unlock_write(mapping);
  		remove_inode_hugepages(inode, hole_start, hole_end);

  		inode_unlock(inode);

  	}
  
  	return 0;
  }
  
  static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
  				loff_t len)
  {
  	struct inode *inode = file_inode(file);
  	struct address_space *mapping = inode->i_mapping;
  	struct hstate *h = hstate_inode(inode);
  	struct vm_area_struct pseudo_vma;
  	struct mm_struct *mm = current->mm;
  	loff_t hpage_size = huge_page_size(h);
  	unsigned long hpage_shift = huge_page_shift(h);
  	pgoff_t start, index, end;
  	int error;
  	u32 hash;
  
  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
  		return -EOPNOTSUPP;
  
  	if (mode & FALLOC_FL_PUNCH_HOLE)
  		return hugetlbfs_punch_hole(inode, offset, len);
  
  	/*
  	 * Default preallocate case.
  	 * For this range, start is rounded down and end is rounded up
  	 * as well as being converted to page offsets.
  	 */
  	start = offset >> hpage_shift;
  	end = (offset + len + hpage_size - 1) >> hpage_shift;

  	inode_lock(inode);

  
  	/* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
  	error = inode_newsize_ok(inode, offset + len);
  	if (error)
  		goto out;
  
  	/*
  	 * Initialize a pseudo vma as this is required by the huge page
  	 * allocation routines.  If NUMA is configured, use page index
  	 * as input to create an allocation policy.
  	 */
  	memset(&pseudo_vma, 0, sizeof(struct vm_area_struct));
  	pseudo_vma.vm_flags = (VM_HUGETLB | VM_MAYSHARE | VM_SHARED);
  	pseudo_vma.vm_file = file;
  
  	for (index = start; index < end; index++) {
  		/*
  		 * This is supposed to be the vaddr where the page is being
  		 * faulted in, but we have no vaddr here.
  		 */
  		struct page *page;
  		unsigned long addr;
  		int avoid_reserve = 0;
  
  		cond_resched();
  
  		/*
  		 * fallocate(2) manpage permits EINTR; we may have been
  		 * interrupted because we are using up too much memory.
  		 */
  		if (signal_pending(current)) {
  			error = -EINTR;
  			break;
  		}
  
  		/* Set numa allocation policy based on index */
  		hugetlb_set_vma_policy(&pseudo_vma, inode, index);
  
  		/* addr is the offset within the file (zero based) */
  		addr = index * hpage_size;
  
  		/* mutex taken here, fault path and hole punch */
  		hash = hugetlb_fault_mutex_hash(h, mm, &pseudo_vma, mapping,
  						index, addr);
  		mutex_lock(&hugetlb_fault_mutex_table[hash]);
  
  		/* See if already present in mapping to avoid alloc/free */
  		page = find_get_page(mapping, index);
  		if (page) {
  			put_page(page);
  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  			hugetlb_drop_vma_policy(&pseudo_vma);
  			continue;
  		}
  
  		/* Allocate page and add to page cache */
  		page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
  		hugetlb_drop_vma_policy(&pseudo_vma);
  		if (IS_ERR(page)) {
  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  			error = PTR_ERR(page);
  			goto out;
  		}
  		clear_huge_page(page, addr, pages_per_huge_page(h));
  		__SetPageUptodate(page);
  		error = huge_add_to_page_cache(page, mapping, index);
  		if (unlikely(error)) {
  			put_page(page);
  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  			goto out;
  		}
  
  		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  
  		/*
  		 * page_put due to reference from alloc_huge_page()
  		 * unlock_page because locked by add_to_page_cache()
  		 */
  		put_page(page);
  		unlock_page(page);
  	}
  
  	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
  		i_size_write(inode, offset + len);

  	inode->i_ctime = current_time(inode);

  out:

  	inode_unlock(inode);

  	return error;
  }

  static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
  {

  	struct inode *inode = d_inode(dentry);

  	struct hstate *h = hstate_inode(inode);

  	int error;
  	unsigned int ia_valid = attr->ia_valid;
  
  	BUG_ON(!inode);

  	error = setattr_prepare(dentry, 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(inode);

  		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;
  }

  /*

   * Hugetlbfs is not reclaimable; therefore its i_mmap_rwsem will never

   * be taken from reclaim -- unlike regular filesystems. This needs an

   * annotation because huge_pmd_share() does an allocation under hugetlb's

   * i_mmap_rwsem.

   */

  static struct lock_class_key hugetlbfs_i_mmap_rwsem_key;

  static struct inode *hugetlbfs_get_inode(struct super_block *sb,
  					struct inode *dir,

  					umode_t mode, dev_t dev)

  {
  	struct inode *inode;

  	struct resv_map *resv_map;
  
  	resv_map = resv_map_alloc();
  	if (!resv_map)
  		return NULL;

  
  	inode = new_inode(sb);
  	if (inode) {
  		struct hugetlbfs_inode_info *info;
  		inode->i_ino = get_next_ino();
  		inode_init_owner(inode, dir, mode);

  		lockdep_set_class(&inode->i_mapping->i_mmap_rwsem,
  				&hugetlbfs_i_mmap_rwsem_key);

  		inode->i_mapping->a_ops = &hugetlbfs_aops;

  		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);

  		inode->i_mapping->private_data = resv_map;

  		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 rwlock_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;

  			inode_nohighmem(inode);

  			break;
  		}

  		lockdep_annotate_inode_mutex_key(inode);

  	} else
  		kref_put(&resv_map->refs, resv_map_release);

  	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(dir);

  		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(dir);

  
  	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 != MIGRATEPAGE_SUCCESS)

  		return rc;
  	migrate_page_copy(newpage, page);

  	return MIGRATEPAGE_SUCCESS;

  }

  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(d_inode(dentry));

  
  	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_iter		= hugetlbfs_read_iter,

  	.mmap			= hugetlbfs_file_mmap,

  	.fsync			= noop_fsync,

  	.get_unmapped_area	= hugetlb_get_unmapped_area,

  	.llseek			= default_llseek,
  	.fallocate		= hugetlbfs_fallocate,

  };

  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,

  };

  enum { 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
  hugetlbfs_size_to_hpages(struct hstate *h, unsigned long long size_opt,
  								int val_type)
  {
  	if (val_type == NO_SIZE)
  		return -1;
  
  	if (val_type == SIZE_PERCENT) {
  		size_opt <<= huge_page_shift(h);
  		size_opt *= h->max_huge_pages;
  		do_div(size_opt, 100);
  	}
  
  	size_opt >>= huge_page_shift(h);
  	return size_opt;
  }

  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 max_size_opt = 0, min_size_opt = 0;
  	int max_val_type = NO_SIZE, min_val_type = 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;

  			max_size_opt = memparse(args[0].from, &rest);
  			max_val_type = SIZE_STD;

  			if (*rest == '%')

  				max_val_type = 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) {

  				pr_err("Unsupported page size %lu MB
  ",

  					ps >> 20);
  				return -EINVAL;
  			}
  			break;
  		}

  		case Opt_min_size: {
  			/* memparse() will accept a K/M/G without a digit */
  			if (!isdigit(*args[0].from))
  				goto bad_val;
  			min_size_opt = memparse(args[0].from, &rest);
  			min_val_type = SIZE_STD;
  			if (*rest == '%')
  				min_val_type = SIZE_PERCENT;
  			break;
  		}

  		default:

  			pr_err("Bad mount option: \"%s\"
  ", p);

  			return -EINVAL;

  			break;
  		}

  	}

  	/*
  	 * Use huge page pool size (in hstate) to convert the size
  	 * options to number of huge pages.  If NO_SIZE, -1 is returned.
  	 */
  	pconfig->max_hpages = hugetlbfs_size_to_hpages(pconfig->hstate,
  						max_size_opt, max_val_type);
  	pconfig->min_hpages = hugetlbfs_size_to_hpages(pconfig->hstate,
  						min_size_opt, min_val_type);
  
  	/*
  	 * If max_size was specified, then min_size must be smaller
  	 */
  	if (max_val_type > NO_SIZE &&
  	    pconfig->min_hpages > pconfig->max_hpages) {
  		pr_err("minimum size can not be greater than maximum size
  ");
  		return -EINVAL;

  	}

  	return 0;

  
  bad_val:

  	pr_err("Bad value '%s' for mount option '%s'
  ", 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.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();
  	config.gid = current_fsgid();

  	config.mode = 0755;

  	config.hstate = &default_hstate;

  	config.min_hpages = -1; /* No default minimum size */

  	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;

  	/*
  	 * Allocate and initialize subpool if maximum or minimum size is
  	 * specified.  Any needed reservations (for minimim size) are taken
  	 * taken when the subpool is created.
  	 */
  	if (config.max_hpages != -1 || config.min_hpages != -1) {
  		sbinfo->spool = hugepage_new_subpool(config.hstate,
  							config.max_hpages,
  							config.min_hpages);

  		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:

  	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[HUGE_MAX_HSTATE];

  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);

  }

  static int get_hstate_idx(int page_size_log)
  {

  	struct hstate *h = hstate_sizelog(page_size_log);

  	if (!h)
  		return -1;
  	return h - hstates;
  }

  static const struct dentry_operations anon_ops = {

  	.d_dname = simple_dname

  };

  /*
   * Note that size should be aligned to proper hugepage size in caller side,
   * otherwise hugetlb_reserve_pages reserves one less hugepages than intended.
   */
  struct file *hugetlb_file_setup(const char *name, size_t size,
  				vm_flags_t acctflag, struct user_struct **user,

  				int creat_flags, int page_size_log)

  {

  	struct file *file = ERR_PTR(-ENOMEM);

  	struct inode *inode;

  	struct path path;

  	struct super_block *sb;

  	struct qstr quick_string;

  	int hstate_idx;
  
  	hstate_idx = get_hstate_idx(page_size_log);
  	if (hstate_idx < 0)
  		return ERR_PTR(-ENODEV);

  	*user = NULL;

  	if (!hugetlbfs_vfsmount[hstate_idx])

  		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);

  			pr_warn_once("%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated
  ",

  				current->comm, current->pid);
  			task_unlock(current);

  		} else {
  			*user = NULL;

  			return ERR_PTR(-EPERM);

  		}

  	}

  	sb = hugetlbfs_vfsmount[hstate_idx]->mnt_sb;

  	quick_string.name = name;

  	quick_string.len = strlen(quick_string.name);
  	quick_string.hash = 0;

  	path.dentry = d_alloc_pseudo(sb, &quick_string);

  	if (!path.dentry)

  		goto out_shm_unlock;

  	d_set_d_op(path.dentry, &anon_ops);

  	path.mnt = mntget(hugetlbfs_vfsmount[hstate_idx]);

  	file = ERR_PTR(-ENOSPC);

  	inode = hugetlbfs_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0);

  	if (!inode)

  		goto out_dentry;

  	if (creat_flags == HUGETLB_SHMFS_INODE)
  		inode->i_flags |= S_PRIVATE;

  	file = ERR_PTR(-ENOMEM);

  	if (hugetlb_reserve_pages(inode, 0,
  			size >> huge_page_shift(hstate_inode(inode)), NULL,
  			acctflag))

  		goto out_inode;

  	d_instantiate(path.dentry, inode);

  	inode->i_size = size;

  	clear_nlink(inode);

  	file = alloc_file(&path, FMODE_WRITE | FMODE_READ,

  			&hugetlbfs_file_operations);

  	if (IS_ERR(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 file;

  }
  
  static int __init init_hugetlbfs_fs(void)
  {

  	struct hstate *h;

  	int error;

  	int i;

  	if (!hugepages_supported()) {

  		pr_info("disabling because there are no supported hugepage sizes
  ");

  		return -ENOTSUPP;
  	}

  	error = -ENOMEM;

  	hugetlbfs_inode_cachep = kmem_cache_create("hugetlbfs_inode_cache",
  					sizeof(struct hugetlbfs_inode_info),

  					0, SLAB_ACCOUNT, init_once);

  	if (hugetlbfs_inode_cachep == NULL)

  		goto out2;

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

  	i = 0;
  	for_each_hstate(h) {
  		char buf[50];
  		unsigned ps_kb = 1U << (h->order + PAGE_SHIFT - 10);

  		snprintf(buf, sizeof(buf), "pagesize=%uK", ps_kb);
  		hugetlbfs_vfsmount[i] = kern_mount_data(&hugetlbfs_fs_type,
  							buf);

  		if (IS_ERR(hugetlbfs_vfsmount[i])) {

  			pr_err("Cannot mount internal hugetlbfs for "

  				"page size %uK", ps_kb);
  			error = PTR_ERR(hugetlbfs_vfsmount[i]);
  			hugetlbfs_vfsmount[i] = NULL;
  		}
  		i++;
  	}
  	/* Non default hstates are optional */
  	if (!IS_ERR_OR_NULL(hugetlbfs_vfsmount[default_hstate_idx]))
  		return 0;

  
   out:

  	kmem_cache_destroy(hugetlbfs_inode_cachep);

   out2:

  	return error;
  }

  fs_initcall(init_hugetlbfs_fs)