Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1745 insertions, 0 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
new file mode 100644
index 0000000000..60fce26ff9
--- /dev/null
+++ b/fs/hugetlbfs/inode.c
@@ -0,0 +1,1745 @@
+/*
+ * 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/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 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
+
+/*
+ * 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).
+	 */
+	vm_flags_set(vma, 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).
+ */
+
+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 = arch_get_mmap_end(addr, len, flags);
+	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 = PAGE_SIZE;
+	info.high_limit = arch_get_mmap_base(addr, 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 = arch_get_mmap_end(addr, len, flags);
+		addr = vm_unmapped_area(&info);
+	}
+
+	return addr;
+}
+
+unsigned long
+generic_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);
+	const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
+
+	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 (mmap_end - 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);
+}
+
+#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)
+{
+	return generic_hugetlb_get_unmapped_area(file, addr, len, pgoff, flags);
+}
+#endif
+
+/*
+ * Someone wants to read @bytes from a HWPOISON hugetlb @page from @offset.
+ * Returns the maximum number of bytes one can read without touching the 1st raw
+ * HWPOISON subpage.
+ *
+ * The implementation borrows the iteration logic from copy_page_to_iter*.
+ */
+static size_t adjust_range_hwpoison(struct page *page, size_t offset, size_t bytes)
+{
+	size_t n = 0;
+	size_t res = 0;
+
+	/* First subpage to start the loop. */
+	page = nth_page(page, offset / PAGE_SIZE);
+	offset %= PAGE_SIZE;
+	while (1) {
+		if (is_raw_hwpoison_page_in_hugepage(page))
+			break;
+
+		/* Safe to read n bytes without touching HWPOISON subpage. */
+		n = min(bytes, (size_t)PAGE_SIZE - offset);
+		res += n;
+		bytes -= n;
+		if (!bytes || !n)
+			break;
+		offset += n;
+		if (offset == PAGE_SIZE) {
+			page = nth_page(page, 1);
+			offset = 0;
+		}
+	}
+
+	return res;
+}
+
+/*
+ * Support for read() - Find the page attached to f_mapping and copy out the
+ * data. This provides functionality similar to filemap_read().
+ */
+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, want;
+
+		/* 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);
+
+			if (!PageHWPoison(page))
+				want = nr;
+			else {
+				/*
+				 * Adjust how many bytes safe to read without
+				 * touching the 1st raw HWPOISON subpage after
+				 * offset.
+				 */
+				want = adjust_range_hwpoison(page, offset, nr);
+				if (want == 0) {
+					put_page(page);
+					retval = -EIO;
+					break;
+				}
+			}
+
+			/*
+			 * We have the page, copy it to user space buffer.
+			 */
+			copied = copy_page_to_iter(page, offset, want, to);
+			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,
+			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 hugetlb_delete_from_page_cache(struct folio *folio)
+{
+	folio_clear_dirty(folio);
+	folio_clear_uptodate(folio);
+	filemap_remove_folio(folio);
+}
+
+/*
+ * Called with i_mmap_rwsem held for inode based vma maps.  This makes
+ * sure vma (and vm_mm) will not go away.  We also hold the hugetlb fault
+ * mutex for the page in the mapping.  So, we can not race with page being
+ * faulted into the vma.
+ */
+static bool hugetlb_vma_maps_page(struct vm_area_struct *vma,
+				unsigned long addr, struct page *page)
+{
+	pte_t *ptep, pte;
+
+	ptep = hugetlb_walk(vma, addr, huge_page_size(hstate_vma(vma)));
+	if (!ptep)
+		return false;
+
+	pte = huge_ptep_get(ptep);
+	if (huge_pte_none(pte) || !pte_present(pte))
+		return false;
+
+	if (pte_page(pte) == page)
+		return true;
+
+	return false;
+}
+
+/*
+ * Can vma_offset_start/vma_offset_end 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.
+ */
+static unsigned long vma_offset_start(struct vm_area_struct *vma, pgoff_t start)
+{
+	unsigned long offset = 0;
+
+	if (vma->vm_pgoff < start)
+		offset = (start - vma->vm_pgoff) << PAGE_SHIFT;
+
+	return vma->vm_start + offset;
+}
+
+static unsigned long vma_offset_end(struct vm_area_struct *vma, pgoff_t end)
+{
+	unsigned long t_end;
+
+	if (!end)
+		return vma->vm_end;
+
+	t_end = ((end - vma->vm_pgoff) << PAGE_SHIFT) + vma->vm_start;
+	if (t_end > vma->vm_end)
+		t_end = vma->vm_end;
+	return t_end;
+}
+
+/*
+ * Called with hugetlb fault mutex held.  Therefore, no more mappings to
+ * this folio can be created while executing the routine.
+ */
+static void hugetlb_unmap_file_folio(struct hstate *h,
+					struct address_space *mapping,
+					struct folio *folio, pgoff_t index)
+{
+	struct rb_root_cached *root = &mapping->i_mmap;
+	struct hugetlb_vma_lock *vma_lock;
+	struct page *page = &folio->page;
+	struct vm_area_struct *vma;
+	unsigned long v_start;
+	unsigned long v_end;
+	pgoff_t start, end;
+
+	start = index * pages_per_huge_page(h);
+	end = (index + 1) * pages_per_huge_page(h);
+
+	i_mmap_lock_write(mapping);
+retry:
+	vma_lock = NULL;
+	vma_interval_tree_foreach(vma, root, start, end - 1) {
+		v_start = vma_offset_start(vma, start);
+		v_end = vma_offset_end(vma, end);
+
+		if (!hugetlb_vma_maps_page(vma, v_start, page))
+			continue;
+
+		if (!hugetlb_vma_trylock_write(vma)) {
+			vma_lock = vma->vm_private_data;
+			/*
+			 * If we can not get vma lock, we need to drop
+			 * immap_sema and take locks in order.  First,
+			 * take a ref on the vma_lock structure so that
+			 * we can be guaranteed it will not go away when
+			 * dropping immap_sema.
+			 */
+			kref_get(&vma_lock->refs);
+			break;
+		}
+
+		unmap_hugepage_range(vma, v_start, v_end, NULL,
+				     ZAP_FLAG_DROP_MARKER);
+		hugetlb_vma_unlock_write(vma);
+	}
+
+	i_mmap_unlock_write(mapping);
+
+	if (vma_lock) {
+		/*
+		 * Wait on vma_lock.  We know it is still valid as we have
+		 * a reference.  We must 'open code' vma locking as we do
+		 * not know if vma_lock is still attached to vma.
+		 */
+		down_write(&vma_lock->rw_sema);
+		i_mmap_lock_write(mapping);
+
+		vma = vma_lock->vma;
+		if (!vma) {
+			/*
+			 * If lock is no longer attached to vma, then just
+			 * unlock, drop our reference and retry looking for
+			 * other vmas.
+			 */
+			up_write(&vma_lock->rw_sema);
+			kref_put(&vma_lock->refs, hugetlb_vma_lock_release);
+			goto retry;
+		}
+
+		/*
+		 * vma_lock is still attached to vma.  Check to see if vma
+		 * still maps page and if so, unmap.
+		 */
+		v_start = vma_offset_start(vma, start);
+		v_end = vma_offset_end(vma, end);
+		if (hugetlb_vma_maps_page(vma, v_start, page))
+			unmap_hugepage_range(vma, v_start, v_end, NULL,
+					     ZAP_FLAG_DROP_MARKER);
+
+		kref_put(&vma_lock->refs, hugetlb_vma_lock_release);
+		hugetlb_vma_unlock_write(vma);
+
+		goto retry;
+	}
+}
+
+static void
+hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end,
+		      zap_flags_t zap_flags)
+{
+	struct vm_area_struct *vma;
+
+	/*
+	 * end == 0 indicates that the entire range after start should be
+	 * unmapped.  Note, end is exclusive, whereas the interval tree takes
+	 * an inclusive "last".
+	 */
+	vma_interval_tree_foreach(vma, root, start, end ? end - 1 : ULONG_MAX) {
+		unsigned long v_start;
+		unsigned long v_end;
+
+		if (!hugetlb_vma_trylock_write(vma))
+			continue;
+
+		v_start = vma_offset_start(vma, start);
+		v_end = vma_offset_end(vma, end);
+
+		unmap_hugepage_range(vma, v_start, v_end, NULL, zap_flags);
+
+		/*
+		 * Note that vma lock only exists for shared/non-private
+		 * vmas.  Therefore, lock is not held when calling
+		 * unmap_hugepage_range for private vmas.
+		 */
+		hugetlb_vma_unlock_write(vma);
+	}
+}
+
+/*
+ * Called with hugetlb fault mutex held.
+ * Returns true if page was actually removed, false otherwise.
+ */
+static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
+					struct address_space *mapping,
+					struct folio *folio, pgoff_t index,
+					bool truncate_op)
+{
+	bool ret = false;
+
+	/*
+	 * If folio is mapped, it was faulted in after being
+	 * unmapped in caller.  Unmap (again) while holding
+	 * the fault mutex.  The mutex will prevent faults
+	 * until we finish removing the folio.
+	 */
+	if (unlikely(folio_mapped(folio)))
+		hugetlb_unmap_file_folio(h, mapping, folio, index);
+
+	folio_lock(folio);
+	/*
+	 * We must remove the folio from page cache 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_FOLIO(folio_test_hugetlb_restore_reserve(folio), folio);
+	hugetlb_delete_from_page_cache(folio);
+	ret = true;
+	if (!truncate_op) {
+		if (unlikely(hugetlb_unreserve_pages(inode, index,
+							index + 1, 1)))
+			hugetlb_fix_reserve_counts(inode);
+	}
+
+	folio_unlock(folio);
+	return ret;
+}
+
+/*
+ * 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 race with truncation.
+ *	During faults, hugetlb_no_page() checks i_size before page allocation,
+ *	and again after obtaining page table lock.  It will 'back out'
+ *	allocations in the truncated range.
+ * 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 folio_batch fbatch;
+	pgoff_t next, index;
+	int i, freed = 0;
+	bool truncate_op = (lend == LLONG_MAX);
+
+	folio_batch_init(&fbatch);
+	next = start;
+	while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
+		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+			struct folio *folio = fbatch.folios[i];
+			u32 hash = 0;
+
+			index = folio->index;
+			hash = hugetlb_fault_mutex_hash(mapping, index);
+			mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
+			/*
+			 * Remove folio that was part of folio_batch.
+			 */
+			if (remove_inode_single_folio(h, inode, mapping, folio,
+							index, truncate_op))
+				freed++;
+
+			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+		}
+		folio_batch_release(&fbatch);
+		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_size_write(inode, offset);
+	i_mmap_lock_write(mapping);
+	if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
+		hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0,
+				      ZAP_FLAG_DROP_MARKER);
+	i_mmap_unlock_write(mapping);
+	remove_inode_hugepages(inode, offset, LLONG_MAX);
+}
+
+static void hugetlbfs_zero_partial_page(struct hstate *h,
+					struct address_space *mapping,
+					loff_t start,
+					loff_t end)
+{
+	pgoff_t idx = start >> huge_page_shift(h);
+	struct folio *folio;
+
+	folio = filemap_lock_folio(mapping, idx);
+	if (IS_ERR(folio))
+		return;
+
+	start = start & ~huge_page_mask(h);
+	end = end & ~huge_page_mask(h);
+	if (!end)
+		end = huge_page_size(h);
+
+	folio_zero_segment(folio, (size_t)start, (size_t)end);
+
+	folio_unlock(folio);
+	folio_put(folio);
+}
+
+static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
+{
+	struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
+	struct address_space *mapping = inode->i_mapping;
+	struct hstate *h = hstate_inode(inode);
+	loff_t hpage_size = huge_page_size(h);
+	loff_t hole_start, hole_end;
+
+	/*
+	 * hole_start and hole_end indicate the full pages within the hole.
+	 */
+	hole_start = round_up(offset, hpage_size);
+	hole_end = round_down(offset + len, hpage_size);
+
+	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 range starts before first full page, zero partial page. */
+	if (offset < hole_start)
+		hugetlbfs_zero_partial_page(h, mapping,
+				offset, min(offset + len, hole_start));
+
+	/* Unmap users of full pages in the hole. */
+	if (hole_end > hole_start) {
+		if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
+			hugetlb_vmdelete_list(&mapping->i_mmap,
+					      hole_start >> PAGE_SHIFT,
+					      hole_end >> PAGE_SHIFT, 0);
+	}
+
+	/* If range extends beyond last full page, zero partial page. */
+	if ((offset + len) > hole_end && (offset + len) > hole_start)
+		hugetlbfs_zero_partial_page(h, mapping,
+				hole_end, offset + len);
+
+	i_mmap_unlock_write(mapping);
+
+	/* Remove full pages from the file. */
+	if (hole_end > hole_start)
+		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);
+	vm_flags_init(&pseudo_vma, 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 folio *folio;
+		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;
+		}
+
+		/* 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(mapping, index);
+		mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
+		/* See if already present in mapping to avoid alloc/free */
+		folio = filemap_get_folio(mapping, index);
+		if (!IS_ERR(folio)) {
+			folio_put(folio);
+			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+			continue;
+		}
+
+		/*
+		 * Allocate folio 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
+		 * folios in these areas, we need to consume the reserves
+		 * to keep reservation accounting consistent.
+		 */
+		hugetlb_set_vma_policy(&pseudo_vma, inode, index);
+		folio = alloc_hugetlb_folio(&pseudo_vma, addr, 0);
+		hugetlb_drop_vma_policy(&pseudo_vma);
+		if (IS_ERR(folio)) {
+			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+			error = PTR_ERR(folio);
+			goto out;
+		}
+		clear_huge_page(&folio->page, addr, pages_per_huge_page(h));
+		__folio_mark_uptodate(folio);
+		error = hugetlb_add_to_page_cache(folio, mapping, index);
+		if (unlikely(error)) {
+			restore_reserve_on_error(h, &pseudo_vma, addr, folio);
+			folio_put(folio);
+			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+			goto out;
+		}
+
+		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+
+		folio_set_hugetlb_migratable(folio);
+		/*
+		 * folio_unlock because locked by hugetlb_add_to_page_cache()
+		 * folio_put() due to reference from alloc_hugetlb_folio()
+		 */
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
+		i_size_write(inode, offset + len);
+	inode_set_ctime_current(inode);
+out:
+	inode_unlock(inode);
+	return error;
+}
+
+static int hugetlbfs_setattr(struct mnt_idmap *idmap,
+			     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(&nop_mnt_idmap, 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(&nop_mnt_idmap, 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_set_ctime_current(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(&nop_mnt_idmap, 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_set_ctime_current(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 hugetlbfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
+			   struct dentry *dentry, umode_t mode, dev_t dev)
+{
+	struct inode *inode;
+
+	inode = hugetlbfs_get_inode(dir->i_sb, dir, mode, dev);
+	if (!inode)
+		return -ENOSPC;
+	dir->i_mtime = inode_set_ctime_current(dir);
+	d_instantiate(dentry, inode);
+	dget(dentry);/* Extra count - pin the dentry in core */
+	return 0;
+}
+
+static int hugetlbfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+			   struct dentry *dentry, umode_t mode)
+{
+	int retval = hugetlbfs_mknod(&nop_mnt_idmap, dir, dentry,
+				     mode | S_IFDIR, 0);
+	if (!retval)
+		inc_nlink(dir);
+	return retval;
+}
+
+static int hugetlbfs_create(struct mnt_idmap *idmap,
+			    struct inode *dir, struct dentry *dentry,
+			    umode_t mode, bool excl)
+{
+	return hugetlbfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
+}
+
+static int hugetlbfs_tmpfile(struct mnt_idmap *idmap,
+			     struct inode *dir, struct file *file,
+			     umode_t mode)
+{
+	struct inode *inode;
+
+	inode = hugetlbfs_get_inode(dir->i_sb, dir, mode | S_IFREG, 0);
+	if (!inode)
+		return -ENOSPC;
+	dir->i_mtime = inode_set_ctime_current(dir);
+	d_tmpfile(file, inode);
+	return finish_open_simple(file, 0);
+}
+
+static int hugetlbfs_symlink(struct mnt_idmap *idmap,
+			     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_mtime = inode_set_ctime_current(dir);
+
+	return error;
+}
+
+#ifdef CONFIG_MIGRATION
+static int hugetlbfs_migrate_folio(struct address_space *mapping,
+				struct folio *dst, struct folio *src,
+				enum migrate_mode mode)
+{
+	int rc;
+
+	rc = migrate_huge_page_move_mapping(mapping, dst, src);
+	if (rc != MIGRATEPAGE_SUCCESS)
+		return rc;
+
+	if (hugetlb_folio_subpool(src)) {
+		hugetlb_set_folio_subpool(dst,
+					hugetlb_folio_subpool(src));
+		hugetlb_set_folio_subpool(src, NULL);
+	}
+
+	if (mode != MIGRATE_SYNC_NO_COPY)
+		folio_migrate_copy(dst, src);
+	else
+		folio_migrate_flags(dst, src);
+
+	return MIGRATEPAGE_SUCCESS;
+}
+#else
+#define hugetlbfs_migrate_folio NULL
+#endif
+
+static int hugetlbfs_error_remove_page(struct address_space *mapping,
+				struct page *page)
+{
+	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 or -1 for max/free/used
+		 * blocks, like simple_statfs() */
+		if (sbinfo->spool) {
+			long free_pages;
+
+			spin_lock_irq(&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_irq(&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 = alloc_inode_sb(sb, 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,
+	.dirty_folio	= noop_dirty_folio,
+	.migrate_folio  = hugetlbfs_migrate_folio,
+	.error_remove_page	= hugetlbfs_error_remove_page,
+};
+
+
+static void init_once(void *foo)
+{
+	struct hugetlbfs_inode_info *ei = 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 (!param->string || !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 (!param->string || !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 / SZ_1M);
+			return -EINVAL;
+		}
+		return 0;
+
+	case Opt_min_size:
+		/* memparse() will accept a K/M/G without a digit */
+		if (!param->string || !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
+	 * 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, 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);
+
+	mnt = hugetlbfs_vfsmount[hstate_idx];
+	if (!mnt)
+		return ERR_PTR(-ENOENT);
+
+	if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
+		struct ucounts *ucounts = current_ucounts();
+
+		if (user_shm_lock(size, ucounts)) {
+			pr_warn_once("%s (%d): Using mlock ulimits for SHM_HUGETLB is obsolete\n",
+				current->comm, current->pid);
+			user_shm_unlock(size, ucounts);
+		}
+		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:
+	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) / SZ_1K);
+	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)