text: /*
   * 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/signal.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/fs_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 <linux/uaccess.h>
  #include <linux/sched/mm.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;
  
  enum hugetlbfs_size_type { NO_SIZE, SIZE_STD, SIZE_PERCENT };
  
  struct hugetlbfs_fs_context {
  	struct hstate		*hstate;
  	unsigned long long	max_size_opt;
  	unsigned long long	min_size_opt;
  	long			max_hpages;
  	long			nr_inodes;
  	long			min_hpages;
  	enum hugetlbfs_size_type max_val_type;
  	enum hugetlbfs_size_type min_val_type;
  	kuid_t			uid;
  	kgid_t			gid;
  	umode_t			mode;
  };
  
  int sysctl_hugetlb_shm_group;
  
  enum hugetlb_param {
  	Opt_gid,
  	Opt_min_size,
  	Opt_mode,
  	Opt_nr_inodes,
  	Opt_pagesize,
  	Opt_size,
  	Opt_uid,
  };
  
  static const struct fs_parameter_spec hugetlb_fs_parameters[] = {
  	fsparam_u32   ("gid",		Opt_gid),
  	fsparam_string("min_size",	Opt_min_size),
  	fsparam_u32oct("mode",		Opt_mode),
  	fsparam_string("nr_inodes",	Opt_nr_inodes),
  	fsparam_string("pagesize",	Opt_pagesize),
  	fsparam_string("size",		Opt_size),
  	fsparam_u32   ("uid",		Opt_uid),
  	{}
  };
  
  #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);
  }
  
  /*
   * Mask used when checking the page offset value passed in via system
   * calls.  This value will be converted to a loff_t which is signed.
   * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the
   * value.  The extra bit (- 1 in the shift value) is to take the sign
   * bit into account.
   */
  #define PGOFF_LOFFT_MAX \
  	(((1UL << (PAGE_SHIFT + 1)) - 1) <<  (BITS_PER_LONG - (PAGE_SHIFT + 1)))
  
  static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	struct inode *inode = file_inode(file);
  	struct hugetlbfs_inode_info *info = HUGETLBFS_I(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 unwinds (may be important on powerpc
  	 * and ia64).
  	 */
  	vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND;
  	vma->vm_ops = &hugetlb_vm_ops;
  
  	ret = seal_check_future_write(info->seals, vma);
  	if (ret)
  		return ret;
  
  	/*
  	 * page based offset in vm_pgoff could be sufficiently large to
  	 * overflow a loff_t when converted to byte offset.  This can
  	 * only happen on architectures where sizeof(loff_t) ==
  	 * sizeof(unsigned long).  So, only check in those instances.
  	 */
  	if (sizeof(unsigned long) == sizeof(loff_t)) {
  		if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
  			return -EINVAL;
  	}
  
  	/* must be huge page aligned */
  	if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
  		return -EINVAL;
  
  	vma_len = (loff_t)(vma->vm_end - vma->vm_start);
  	len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
  	/* check for overflow */
  	if (len < vma_len)
  		return -EINVAL;
  
  	inode_lock(inode);
  	file_accessed(file);
  
  	ret = -ENOMEM;
  	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)
  		i_size_write(inode, len);
  out:
  	inode_unlock(inode);
  
  	return ret;
  }
  
  /*
   * Called under mmap_write_lock(mm).
   */
  
  #ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
  static unsigned long
  hugetlb_get_unmapped_area_bottomup(struct file *file, unsigned long addr,
  		unsigned long len, unsigned long pgoff, unsigned long flags)
  {
  	struct hstate *h = hstate_file(file);
  	struct vm_unmapped_area_info info;
  
  	info.flags = 0;
  	info.length = len;
  	info.low_limit = current->mm->mmap_base;
  	info.high_limit = TASK_SIZE;
  	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
  	info.align_offset = 0;
  	return vm_unmapped_area(&info);
  }
  
  static unsigned long
  hugetlb_get_unmapped_area_topdown(struct file *file, unsigned long addr,
  		unsigned long len, unsigned long pgoff, unsigned long flags)
  {
  	struct hstate *h = hstate_file(file);
  	struct vm_unmapped_area_info info;
  
  	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
  	info.length = len;
  	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
  	info.high_limit = current->mm->mmap_base;
  	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
  	info.align_offset = 0;
  	addr = vm_unmapped_area(&info);
  
  	/*
  	 * A failed mmap() very likely causes application failure,
  	 * so fall back to the bottom-up function here. This scenario
  	 * can happen with large stack limits and large mmap()
  	 * allocations.
  	 */
  	if (unlikely(offset_in_page(addr))) {
  		VM_BUG_ON(addr != -ENOMEM);
  		info.flags = 0;
  		info.low_limit = current->mm->mmap_base;
  		info.high_limit = TASK_SIZE;
  		addr = vm_unmapped_area(&info);
  	}
  
  	return addr;
  }
  
  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);
  
  	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 <= vm_start_gap(vma)))
  			return addr;
  	}
  
  	/*
  	 * Use mm->get_unmapped_area value as a hint to use topdown routine.
  	 * If architectures have special needs, they should define their own
  	 * version of hugetlb_get_unmapped_area.
  	 */
  	if (mm->get_unmapped_area == arch_get_unmapped_area_topdown)
  		return hugetlb_get_unmapped_area_topdown(file, addr, len,
  				pgoff, flags);
  	return hugetlb_get_unmapped_area_bottomup(file, addr, len,
  			pgoff, flags);
  }
  #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 generic_file_buffered_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_cached *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/reserve
   *	maps and global counts.  Page faults can not race with truncation
   *	in this routine.  hugetlb_no_page() holds i_mmap_rwsem and prevents
   *	page faults in the truncated range by checking i_size.  i_size is
   *	modified while holding i_mmap_rwsem.
   * 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/reserve map
   *	deleted.  The region/reserve 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 pagevec pvec;
  	pgoff_t next, index;
  	int i, freed = 0;
  	bool truncate_op = (lend == LLONG_MAX);
  
  	pagevec_init(&pvec);
  	next = start;
  	while (next < end) {
  		/*
  		 * When no more pages are found, we are done.
  		 */
  		if (!pagevec_lookup_range(&pvec, mapping, &next, end - 1))
  			break;
  
  		for (i = 0; i < pagevec_count(&pvec); ++i) {
  			struct page *page = pvec.pages[i];
  			u32 hash = 0;
  
  			index = page->index;
  			if (!truncate_op) {
  				/*
  				 * Only need to hold the fault mutex in the
  				 * hole punch case.  This prevents races with
  				 * page faults.  Races are not possible in the
  				 * case of truncation.
  				 */
  				hash = hugetlb_fault_mutex_hash(mapping, index);
  				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);
  
  				mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  				i_mmap_lock_write(mapping);
  				mutex_lock(&hugetlb_fault_mutex_table[hash]);
  				hugetlb_vmdelete_list(&mapping->i_mmap,
  					index * pages_per_huge_page(h),
  					(index + 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(HPageRestoreReserve(page));
  			remove_huge_page(page);
  			freed++;
  			if (!truncate_op) {
  				if (unlikely(hugetlb_unreserve_pages(inode,
  							index, index + 1, 1)))
  					hugetlb_fix_reserve_counts(inode);
  			}
  
  			unlock_page(page);
  			if (!truncate_op)
  				mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  		}
  		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);
  
  	/*
  	 * Get the resv_map from the address space embedded in the inode.
  	 * This is the address space which points to any resv_map allocated
  	 * at inode creation time.  If this is a device special inode,
  	 * i_mapping may not point to the original address space.
  	 */
  	resv_map = (struct resv_map *)(&inode->i_data)->private_data;
  	/* Only regular and link inodes have associated reserve maps */
  	if (resv_map)
  		resv_map_release(&resv_map->refs);
  	clear_inode(inode);
  }
  
  static void 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_mmap_lock_write(mapping);
  	i_size_write(inode, offset);
  	if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
  		hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);
  	i_mmap_unlock_write(mapping);
  	remove_inode_hugepages(inode, offset, LLONG_MAX);
  }
  
  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;
  		struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
  
  		inode_lock(inode);
  
  		/* protected by i_rwsem */
  		if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
  			inode_unlock(inode);
  			return -EPERM;
  		}
  
  		i_mmap_lock_write(mapping);
  		if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
  			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 hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
  	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;
  
  	if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
  		error = -EPERM;
  		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.
  	 */
  	vma_init(&pseudo_vma, mm);
  	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;
  
  		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;
  
  		/*
  		 * fault mutex taken here, protects against fault path
  		 * and hole punch.  inode_lock previously taken protects
  		 * against truncation.
  		 */
  		hash = hugetlb_fault_mutex_hash(mapping, index);
  		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 without setting the avoid_reserve argument.
  		 * There certainly are no reserves associated with the
  		 * pseudo_vma.  However, there could be shared mappings with
  		 * reserves for the file at the inode level.  If we fallocate
  		 * pages in these areas, we need to consume the reserves
  		 * to keep reservation accounting consistent.
  		 */
  		page = alloc_huge_page(&pseudo_vma, addr, 0);
  		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)) {
  			restore_reserve_on_error(h, &pseudo_vma, addr, page);
  			put_page(page);
  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  			goto out;
  		}
  
  		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
  
  		SetHPageMigratable(page);
  		/*
  		 * unlock_page because locked by add_to_page_cache()
  		 * put_page() due to reference from alloc_huge_page()
  		 */
  		unlock_page(page);
  		put_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 user_namespace *mnt_userns,
  			     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;
  	struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
  
  	error = setattr_prepare(&init_user_ns, dentry, attr);
  	if (error)
  		return error;
  
  	if (ia_valid & ATTR_SIZE) {
  		loff_t oldsize = inode->i_size;
  		loff_t newsize = attr->ia_size;
  
  		if (newsize & ~huge_page_mask(h))
  			return -EINVAL;
  		/* protected by i_rwsem */
  		if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
  		    (newsize > oldsize && (info->seals & F_SEAL_GROW)))
  			return -EPERM;
  		hugetlb_vmtruncate(inode, newsize);
  	}
  
  	setattr_copy(&init_user_ns, inode, attr);
  	mark_inode_dirty(inode);
  	return 0;
  }
  
  static struct inode *hugetlbfs_get_root(struct super_block *sb,
  					struct hugetlbfs_fs_context *ctx)
  {
  	struct inode *inode;
  
  	inode = new_inode(sb);
  	if (inode) {
  		inode->i_ino = get_next_ino();
  		inode->i_mode = S_IFDIR | ctx->mode;
  		inode->i_uid = ctx->uid;
  		inode->i_gid = ctx->gid;
  		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
  		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 = NULL;
  
  	/*
  	 * Reserve maps are only needed for inodes that can have associated
  	 * page allocations.
  	 */
  	if (S_ISREG(mode) || S_ISLNK(mode)) {
  		resv_map = resv_map_alloc();
  		if (!resv_map)
  			return NULL;
  	}
  
  	inode = new_inode(sb);
  	if (inode) {
  		struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
  
  		inode->i_ino = get_next_ino();
  		inode_init_owner(&init_user_ns, 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->seals = F_SEAL_SEAL;
  		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 {
  		if (resv_map)
  			kref_put(&resv_map->refs, resv_map_release);
  	}
  
  	return inode;
  }
  
  /*
   * File creation. Allocate an inode, and we're done..
   */
  static int do_hugetlbfs_mknod(struct inode *dir,
  			struct dentry *dentry,
  			umode_t mode,
  			dev_t dev,
  			bool tmpfile)
  {
  	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);
  		if (tmpfile) {
  			d_tmpfile(dentry, inode);
  		} else {
  			d_instantiate(dentry, inode);
  			dget(dentry);/* Extra count - pin the dentry in core */
  		}
  		error = 0;
  	}
  	return error;
  }
  
  static int hugetlbfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
  			   struct dentry *dentry, umode_t mode, dev_t dev)
  {
  	return do_hugetlbfs_mknod(dir, dentry, mode, dev, false);
  }
  
  static int hugetlbfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
  			   struct dentry *dentry, umode_t mode)
  {
  	int retval = hugetlbfs_mknod(&init_user_ns, dir, dentry,
  				     mode | S_IFDIR, 0);
  	if (!retval)
  		inc_nlink(dir);
  	return retval;
  }
  
  static int hugetlbfs_create(struct user_namespace *mnt_userns,
  			    struct inode *dir, struct dentry *dentry,
  			    umode_t mode, bool excl)
  {
  	return hugetlbfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
  }
  
  static int hugetlbfs_tmpfile(struct user_namespace *mnt_userns,
  			     struct inode *dir, struct dentry *dentry,
  			     umode_t mode)
  {
  	return do_hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0, true);
  }
  
  static int hugetlbfs_symlink(struct user_namespace *mnt_userns,
  			     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;
  }
  
  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;
  
  	if (hugetlb_page_subpool(page)) {
  		hugetlb_set_page_subpool(newpage, hugetlb_page_subpool(page));
  		hugetlb_set_page_subpool(page, NULL);
  	}
  
  	if (mode != MIGRATE_SYNC_NO_COPY)
  		migrate_page_copy(newpage, page);
  	else
  		migrate_page_states(newpage, page);
  
  	return MIGRATEPAGE_SUCCESS;
  }
  
  static int hugetlbfs_error_remove_page(struct address_space *mapping,
  				struct page *page)
  {
  	struct inode *inode = mapping->host;
  	pgoff_t index = page->index;
  
  	remove_huge_page(page);
  	if (unlikely(hugetlb_unreserve_pages(inode, index, index + 1, 1)))
  		hugetlb_fix_reserve_counts(inode);
  
  	return 0;
  }
  
  /*
   * Display the mount options in /proc/mounts.
   */
  static int hugetlbfs_show_options(struct seq_file *m, struct dentry *root)
  {
  	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(root->d_sb);
  	struct hugepage_subpool *spool = sbinfo->spool;
  	unsigned long hpage_size = huge_page_size(sbinfo->hstate);
  	unsigned hpage_shift = huge_page_shift(sbinfo->hstate);
  	char mod;
  
  	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
  		seq_printf(m, ",uid=%u",
  			   from_kuid_munged(&init_user_ns, sbinfo->uid));
  	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
  		seq_printf(m, ",gid=%u",
  			   from_kgid_munged(&init_user_ns, sbinfo->gid));
  	if (sbinfo->mode != 0755)
  		seq_printf(m, ",mode=%o", sbinfo->mode);
  	if (sbinfo->max_inodes != -1)
  		seq_printf(m, ",nr_inodes=%lu", sbinfo->max_inodes);
  
  	hpage_size /= 1024;
  	mod = 'K';
  	if (hpage_size >= 1024) {
  		hpage_size /= 1024;
  		mod = 'M';
  	}
  	seq_printf(m, ",pagesize=%lu%c", hpage_size, mod);
  	if (spool) {
  		if (spool->max_hpages != -1)
  			seq_printf(m, ",size=%llu",
  				   (unsigned long long)spool->max_hpages << hpage_shift);
  		if (spool->min_hpages != -1)
  			seq_printf(m, ",min_size=%llu",
  				   (unsigned long long)spool->min_hpages << hpage_shift);
  	}
  	return 0;
  }
  
  static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
  {
  	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(dentry->d_sb);
  	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;
  	}
  
  	/*
  	 * Any time after allocation, hugetlbfs_destroy_inode can be called
  	 * for the inode.  mpol_free_shared_policy is unconditionally called
  	 * as part of hugetlbfs_destroy_inode.  So, initialize policy here
  	 * in case of a quick call to destroy.
  	 *
  	 * Note that the policy is initialized even if we are creating a
  	 * private inode.  This simplifies hugetlbfs_destroy_inode.
  	 */
  	mpol_shared_policy_init(&p->policy, NULL);
  
  	return &p->vfs_inode;
  }
  
  static void hugetlbfs_free_inode(struct inode *inode)
  {
  	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);
  }
  
  static const struct address_space_operations hugetlbfs_aops = {
  	.write_begin	= hugetlbfs_write_begin,
  	.write_end	= hugetlbfs_write_end,
  	.set_page_dirty	=  __set_page_dirty_no_writeback,
  	.migratepage    = hugetlbfs_migrate_page,
  	.error_remove_page	= hugetlbfs_error_remove_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,
  	.tmpfile	= hugetlbfs_tmpfile,
  };
  
  static const struct inode_operations hugetlbfs_inode_operations = {
  	.setattr	= hugetlbfs_setattr,
  };
  
  static const struct super_operations hugetlbfs_ops = {
  	.alloc_inode    = hugetlbfs_alloc_inode,
  	.free_inode     = hugetlbfs_free_inode,
  	.destroy_inode  = hugetlbfs_destroy_inode,
  	.evict_inode	= hugetlbfs_evict_inode,
  	.statfs		= hugetlbfs_statfs,
  	.put_super	= hugetlbfs_put_super,
  	.show_options	= hugetlbfs_show_options,
  };
  
  /*
   * 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
  hugetlbfs_size_to_hpages(struct hstate *h, unsigned long long size_opt,
  			 enum hugetlbfs_size_type 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;
  }
  
  /*
   * Parse one mount parameter.
   */
  static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
  {
  	struct hugetlbfs_fs_context *ctx = fc->fs_private;
  	struct fs_parse_result result;
  	char *rest;
  	unsigned long ps;
  	int opt;
  
  	opt = fs_parse(fc, hugetlb_fs_parameters, param, &result);
  	if (opt < 0)
  		return opt;
  
  	switch (opt) {
  	case Opt_uid:
  		ctx->uid = make_kuid(current_user_ns(), result.uint_32);
  		if (!uid_valid(ctx->uid))
  			goto bad_val;
  		return 0;
  
  	case Opt_gid:
  		ctx->gid = make_kgid(current_user_ns(), result.uint_32);
  		if (!gid_valid(ctx->gid))
  			goto bad_val;
  		return 0;
  
  	case Opt_mode:
  		ctx->mode = result.uint_32 & 01777U;
  		return 0;
  
  	case Opt_size:
  		/* memparse() will accept a K/M/G without a digit */
  		if (!isdigit(param->string[0]))
  			goto bad_val;
  		ctx->max_size_opt = memparse(param->string, &rest);
  		ctx->max_val_type = SIZE_STD;
  		if (*rest == '%')
  			ctx->max_val_type = SIZE_PERCENT;
  		return 0;
  
  	case Opt_nr_inodes:
  		/* memparse() will accept a K/M/G without a digit */
  		if (!isdigit(param->string[0]))
  			goto bad_val;
  		ctx->nr_inodes = memparse(param->string, &rest);
  		return 0;
  
  	case Opt_pagesize:
  		ps = memparse(param->string, &rest);
  		ctx->hstate = size_to_hstate(ps);
  		if (!ctx->hstate) {
  			pr_err("Unsupported page size %lu MB\n", ps >> 20);
  			return -EINVAL;
  		}
  		return 0;
  
  	case Opt_min_size:
  		/* memparse() will accept a K/M/G without a digit */
  		if (!isdigit(param->string[0]))
  			goto bad_val;
  		ctx->min_size_opt = memparse(param->string, &rest);
  		ctx->min_val_type = SIZE_STD;
  		if (*rest == '%')
  			ctx->min_val_type = SIZE_PERCENT;
  		return 0;
  
  	default:
  		return -EINVAL;
  	}
  
  bad_val:
  	return invalfc(fc, "Bad value '%s' for mount option '%s'\n",
  		      param->string, param->key);
  }
  
  /*
   * Validate the parsed options.
   */
  static int hugetlbfs_validate(struct fs_context *fc)
  {
  	struct hugetlbfs_fs_context *ctx = fc->fs_private;
  
  	/*
  	 * Use huge page pool size (in hstate) to convert the size
  	 * options to number of huge pages.  If NO_SIZE, -1 is returned.
  	 */
  	ctx->max_hpages = hugetlbfs_size_to_hpages(ctx->hstate,
  						   ctx->max_size_opt,
  						   ctx->max_val_type);
  	ctx->min_hpages = hugetlbfs_size_to_hpages(ctx->hstate,
  						   ctx->min_size_opt,
  						   ctx->min_val_type);
  
  	/*
  	 * If max_size was specified, then min_size must be smaller
  	 */
  	if (ctx->max_val_type > NO_SIZE &&
  	    ctx->min_hpages > ctx->max_hpages) {
  		pr_err("Minimum size can not be greater than maximum size\n");
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  static int
  hugetlbfs_fill_super(struct super_block *sb, struct fs_context *fc)
  {
  	struct hugetlbfs_fs_context *ctx = fc->fs_private;
  	struct hugetlbfs_sb_info *sbinfo;
  
  	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->hstate		= ctx->hstate;
  	sbinfo->max_inodes	= ctx->nr_inodes;
  	sbinfo->free_inodes	= ctx->nr_inodes;
  	sbinfo->spool		= NULL;
  	sbinfo->uid		= ctx->uid;
  	sbinfo->gid		= ctx->gid;
  	sbinfo->mode		= ctx->mode;
  
  	/*
  	 * Allocate and initialize subpool if maximum or minimum size is
  	 * specified.  Any needed reservations (for minimum size) are taken
  	 * taken when the subpool is created.
  	 */
  	if (ctx->max_hpages != -1 || ctx->min_hpages != -1) {
  		sbinfo->spool = hugepage_new_subpool(ctx->hstate,
  						     ctx->max_hpages,
  						     ctx->min_hpages);
  		if (!sbinfo->spool)
  			goto out_free;
  	}
  	sb->s_maxbytes = MAX_LFS_FILESIZE;
  	sb->s_blocksize = huge_page_size(ctx->hstate);
  	sb->s_blocksize_bits = huge_page_shift(ctx->hstate);
  	sb->s_magic = HUGETLBFS_MAGIC;
  	sb->s_op = &hugetlbfs_ops;
  	sb->s_time_gran = 1;
  
  	/*
  	 * Due to the special and limited functionality of hugetlbfs, it does
  	 * not work well as a stacking filesystem.
  	 */
  	sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
  	sb->s_root = d_make_root(hugetlbfs_get_root(sb, ctx));
  	if (!sb->s_root)
  		goto out_free;
  	return 0;
  out_free:
  	kfree(sbinfo->spool);
  	kfree(sbinfo);
  	return -ENOMEM;
  }
  
  static int hugetlbfs_get_tree(struct fs_context *fc)
  {
  	int err = hugetlbfs_validate(fc);
  	if (err)
  		return err;
  	return get_tree_nodev(fc, hugetlbfs_fill_super);
  }
  
  static void hugetlbfs_fs_context_free(struct fs_context *fc)
  {
  	kfree(fc->fs_private);
  }
  
  static const struct fs_context_operations hugetlbfs_fs_context_ops = {
  	.free		= hugetlbfs_fs_context_free,
  	.parse_param	= hugetlbfs_parse_param,
  	.get_tree	= hugetlbfs_get_tree,
  };
  
  static int hugetlbfs_init_fs_context(struct fs_context *fc)
  {
  	struct hugetlbfs_fs_context *ctx;
  
  	ctx = kzalloc(sizeof(struct hugetlbfs_fs_context), GFP_KERNEL);
  	if (!ctx)
  		return -ENOMEM;
  
  	ctx->max_hpages	= -1; /* No limit on size by default */
  	ctx->nr_inodes	= -1; /* No limit on number of inodes by default */
  	ctx->uid	= current_fsuid();
  	ctx->gid	= current_fsgid();
  	ctx->mode	= 0755;
  	ctx->hstate	= &default_hstate;
  	ctx->min_hpages	= -1; /* No default minimum size */
  	ctx->max_val_type = NO_SIZE;
  	ctx->min_val_type = NO_SIZE;
  	fc->fs_private = ctx;
  	fc->ops	= &hugetlbfs_fs_context_ops;
  	return 0;
  }
  
  static struct file_system_type hugetlbfs_fs_type = {
  	.name			= "hugetlbfs",
  	.init_fs_context	= hugetlbfs_init_fs_context,
  	.parameters		= hugetlb_fs_parameters,
  	.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 hstate_index(h);
  }
  
  /*
   * 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 ucounts **ucounts,
  				int creat_flags, int page_size_log)
  {
  	struct inode *inode;
  	struct vfsmount *mnt;
  	int hstate_idx;
  	struct file *file;
  
  	hstate_idx = get_hstate_idx(page_size_log);
  	if (hstate_idx < 0)
  		return ERR_PTR(-ENODEV);
  
  	*ucounts = NULL;
  	mnt = hugetlbfs_vfsmount[hstate_idx];
  	if (!mnt)
  		return ERR_PTR(-ENOENT);
  
  	if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
  		*ucounts = current_ucounts();
  		if (user_shm_lock(size, *ucounts)) {
  			task_lock(current);
  			pr_warn_once("%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated\n",
  				current->comm, current->pid);
  			task_unlock(current);
  		} else {
  			*ucounts = NULL;
  			return ERR_PTR(-EPERM);
  		}
  	}
  
  	file = ERR_PTR(-ENOSPC);
  	inode = hugetlbfs_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0);
  	if (!inode)
  		goto out;
  	if (creat_flags == HUGETLB_SHMFS_INODE)
  		inode->i_flags |= S_PRIVATE;
  
  	inode->i_size = size;
  	clear_nlink(inode);
  
  	if (!hugetlb_reserve_pages(inode, 0,
  			size >> huge_page_shift(hstate_inode(inode)), NULL,
  			acctflag))
  		file = ERR_PTR(-ENOMEM);
  	else
  		file = alloc_file_pseudo(inode, mnt, name, O_RDWR,
  					&hugetlbfs_file_operations);
  	if (!IS_ERR(file))
  		return file;
  
  	iput(inode);
  out:
  	if (*ucounts) {
  		user_shm_unlock(size, *ucounts);
  		*ucounts = NULL;
  	}
  	return file;
  }
  
  static struct vfsmount *__init mount_one_hugetlbfs(struct hstate *h)
  {
  	struct fs_context *fc;
  	struct vfsmount *mnt;
  
  	fc = fs_context_for_mount(&hugetlbfs_fs_type, SB_KERNMOUNT);
  	if (IS_ERR(fc)) {
  		mnt = ERR_CAST(fc);
  	} else {
  		struct hugetlbfs_fs_context *ctx = fc->fs_private;
  		ctx->hstate = h;
  		mnt = fc_mount(fc);
  		put_fs_context(fc);
  	}
  	if (IS_ERR(mnt))
  		pr_err("Cannot mount internal hugetlbfs for page size %luK",
  		       huge_page_size(h) >> 10);
  	return mnt;
  }
  
  static int __init init_hugetlbfs_fs(void)
  {
  	struct vfsmount *mnt;
  	struct hstate *h;
  	int error;
  	int i;
  
  	if (!hugepages_supported()) {
  		pr_info("disabling because there are no supported hugepage sizes\n");
  		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 out;
  
  	error = register_filesystem(&hugetlbfs_fs_type);
  	if (error)
  		goto out_free;
  
  	/* default hstate mount is required */
  	mnt = mount_one_hugetlbfs(&default_hstate);
  	if (IS_ERR(mnt)) {
  		error = PTR_ERR(mnt);
  		goto out_unreg;
  	}
  	hugetlbfs_vfsmount[default_hstate_idx] = mnt;
  
  	/* other hstates are optional */
  	i = 0;
  	for_each_hstate(h) {
  		if (i == default_hstate_idx) {
  			i++;
  			continue;
  		}
  
  		mnt = mount_one_hugetlbfs(h);
  		if (IS_ERR(mnt))
  			hugetlbfs_vfsmount[i] = NULL;
  		else
  			hugetlbfs_vfsmount[i] = mnt;
  		i++;
  	}
  
  	return 0;
  
   out_unreg:
  	(void)unregister_filesystem(&hugetlbfs_fs_type);
   out_free:
  	kmem_cache_destroy(hugetlbfs_inode_cachep);
   out:
  	return error;
  }
  fs_initcall(init_hugetlbfs_fs)
  