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1// SPDX-License-Identifier: GPL-2.0-or-later2/* file-nommu.c: no-MMU version of ramfs3 *4 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.5 * Written by David Howells (dhowells@redhat.com)6 */7 8#include <linux/module.h>9#include <linux/fs.h>10#include <linux/mm.h>11#include <linux/pagemap.h>12#include <linux/highmem.h>13#include <linux/init.h>14#include <linux/string.h>15#include <linux/backing-dev.h>16#include <linux/ramfs.h>17#include <linux/pagevec.h>18#include <linux/mman.h>19#include <linux/sched.h>20#include <linux/slab.h>21 22#include <linux/uaccess.h>23#include "internal.h"24 25static int ramfs_nommu_setattr(struct mnt_idmap *, struct dentry *, struct iattr *);26static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,27 unsigned long addr,28 unsigned long len,29 unsigned long pgoff,30 unsigned long flags);31static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma);32 33static unsigned ramfs_mmap_capabilities(struct file *file)34{35 return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ |36 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;37}38 39const struct file_operations ramfs_file_operations = {40 .mmap_capabilities = ramfs_mmap_capabilities,41 .mmap = ramfs_nommu_mmap,42 .get_unmapped_area = ramfs_nommu_get_unmapped_area,43 .read_iter = generic_file_read_iter,44 .write_iter = generic_file_write_iter,45 .fsync = noop_fsync,46 .splice_read = filemap_splice_read,47 .splice_write = iter_file_splice_write,48 .llseek = generic_file_llseek,49};50 51const struct inode_operations ramfs_file_inode_operations = {52 .setattr = ramfs_nommu_setattr,53 .getattr = simple_getattr,54};55 56/*****************************************************************************/57/*58 * add a contiguous set of pages into a ramfs inode when it's truncated from59 * size 0 on the assumption that it's going to be used for an mmap of shared60 * memory61 */62int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)63{64 unsigned long npages, xpages, loop;65 struct page *pages;66 unsigned order;67 void *data;68 int ret;69 gfp_t gfp = mapping_gfp_mask(inode->i_mapping);70 71 /* make various checks */72 order = get_order(newsize);73 if (unlikely(order > MAX_PAGE_ORDER))74 return -EFBIG;75 76 ret = inode_newsize_ok(inode, newsize);77 if (ret)78 return ret;79 80 i_size_write(inode, newsize);81 82 /* allocate enough contiguous pages to be able to satisfy the83 * request */84 pages = alloc_pages(gfp, order);85 if (!pages)86 return -ENOMEM;87 88 /* split the high-order page into an array of single pages */89 xpages = 1UL << order;90 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;91 92 split_page(pages, order);93 94 /* trim off any pages we don't actually require */95 for (loop = npages; loop < xpages; loop++)96 __free_page(pages + loop);97 98 /* clear the memory we allocated */99 newsize = PAGE_SIZE * npages;100 data = page_address(pages);101 memset(data, 0, newsize);102 103 /* attach all the pages to the inode's address space */104 for (loop = 0; loop < npages; loop++) {105 struct page *page = pages + loop;106 107 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,108 gfp);109 if (ret < 0)110 goto add_error;111 112 /* prevent the page from being discarded on memory pressure */113 SetPageDirty(page);114 SetPageUptodate(page);115 116 unlock_page(page);117 put_page(page);118 }119 120 return 0;121 122add_error:123 while (loop < npages)124 __free_page(pages + loop++);125 return ret;126}127 128/*****************************************************************************/129/*130 *131 */132static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)133{134 int ret;135 136 /* assume a truncate from zero size is going to be for the purposes of137 * shared mmap */138 if (size == 0) {139 if (unlikely(newsize >> 32))140 return -EFBIG;141 142 return ramfs_nommu_expand_for_mapping(inode, newsize);143 }144 145 /* check that a decrease in size doesn't cut off any shared mappings */146 if (newsize < size) {147 ret = nommu_shrink_inode_mappings(inode, size, newsize);148 if (ret < 0)149 return ret;150 }151 152 truncate_setsize(inode, newsize);153 return 0;154}155 156/*****************************************************************************/157/*158 * handle a change of attributes159 * - we're specifically interested in a change of size160 */161static int ramfs_nommu_setattr(struct mnt_idmap *idmap,162 struct dentry *dentry, struct iattr *ia)163{164 struct inode *inode = d_inode(dentry);165 unsigned int old_ia_valid = ia->ia_valid;166 int ret = 0;167 168 /* POSIX UID/GID verification for setting inode attributes */169 ret = setattr_prepare(&nop_mnt_idmap, dentry, ia);170 if (ret)171 return ret;172 173 /* pick out size-changing events */174 if (ia->ia_valid & ATTR_SIZE) {175 loff_t size = inode->i_size;176 177 if (ia->ia_size != size) {178 ret = ramfs_nommu_resize(inode, ia->ia_size, size);179 if (ret < 0 || ia->ia_valid == ATTR_SIZE)180 goto out;181 } else {182 /* we skipped the truncate but must still update183 * timestamps184 */185 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;186 }187 }188 189 setattr_copy(&nop_mnt_idmap, inode, ia);190 out:191 ia->ia_valid = old_ia_valid;192 return ret;193}194 195/*****************************************************************************/196/*197 * try to determine where a shared mapping can be made198 * - we require that:199 * - the pages to be mapped must exist200 * - the pages be physically contiguous in sequence201 */202static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,203 unsigned long addr, unsigned long len,204 unsigned long pgoff, unsigned long flags)205{206 unsigned long maxpages, lpages, nr_folios, loop, ret, nr_pages, pfn;207 struct inode *inode = file_inode(file);208 struct folio_batch fbatch;209 loff_t isize;210 211 /* the mapping mustn't extend beyond the EOF */212 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;213 isize = i_size_read(inode);214 215 ret = -ENOSYS;216 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;217 if (pgoff >= maxpages)218 goto out;219 220 if (maxpages - pgoff < lpages)221 goto out;222 223 /* gang-find the pages */224 folio_batch_init(&fbatch);225 nr_pages = 0;226repeat:227 nr_folios = filemap_get_folios_contig(inode->i_mapping, &pgoff,228 ULONG_MAX, &fbatch);229 if (!nr_folios) {230 ret = -ENOSYS;231 return ret;232 }233 234 if (ret == -ENOSYS) {235 ret = (unsigned long) folio_address(fbatch.folios[0]);236 pfn = folio_pfn(fbatch.folios[0]);237 }238 /* check the pages for physical adjacency */239 for (loop = 0; loop < nr_folios; loop++) {240 if (pfn + nr_pages != folio_pfn(fbatch.folios[loop])) {241 ret = -ENOSYS;242 goto out_free; /* leave if not physical adjacent */243 }244 nr_pages += folio_nr_pages(fbatch.folios[loop]);245 if (nr_pages >= lpages)246 goto out_free; /* successfully found desired pages*/247 }248 249 if (nr_pages < lpages) {250 folio_batch_release(&fbatch);251 goto repeat; /* loop if pages are missing */252 }253 /* okay - all conditions fulfilled */254 255out_free:256 folio_batch_release(&fbatch);257out:258 return ret;259}260 261/*****************************************************************************/262/*263 * set up a mapping for shared memory segments264 */265static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)266{267 if (!is_nommu_shared_mapping(vma->vm_flags))268 return -ENOSYS;269 270 file_accessed(file);271 vma->vm_ops = &generic_file_vm_ops;272 return 0;273}274