/* * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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 += 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++; 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->i_ctime = current_time(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->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(&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->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 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_ctime = dir->i_mtime = current_time(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_ctime = dir->i_mtime = current_time(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_ctime = dir->i_mtime = current_time(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)