1 /* file-nommu.c: no-MMU version of ramfs 2 * 3 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/module.h> 13 #include <linux/fs.h> 14 #include <linux/mm.h> 15 #include <linux/pagemap.h> 16 #include <linux/highmem.h> 17 #include <linux/init.h> 18 #include <linux/string.h> 19 #include <linux/backing-dev.h> 20 #include <linux/ramfs.h> 21 #include <linux/pagevec.h> 22 #include <linux/mman.h> 23 #include <linux/sched.h> 24 #include <linux/slab.h> 25 26 #include <asm/uaccess.h> 27 #include "internal.h" 28 29 static int ramfs_nommu_setattr(struct dentry *, struct iattr *); 30 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 31 unsigned long addr, 32 unsigned long len, 33 unsigned long pgoff, 34 unsigned long flags); 35 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma); 36 37 static unsigned ramfs_mmap_capabilities(struct file *file) 38 { 39 return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ | 40 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC; 41 } 42 43 const struct file_operations ramfs_file_operations = { 44 .mmap_capabilities = ramfs_mmap_capabilities, 45 .mmap = ramfs_nommu_mmap, 46 .get_unmapped_area = ramfs_nommu_get_unmapped_area, 47 .read_iter = generic_file_read_iter, 48 .write_iter = generic_file_write_iter, 49 .fsync = noop_fsync, 50 .splice_read = generic_file_splice_read, 51 .splice_write = iter_file_splice_write, 52 .llseek = generic_file_llseek, 53 }; 54 55 const struct inode_operations ramfs_file_inode_operations = { 56 .setattr = ramfs_nommu_setattr, 57 .getattr = simple_getattr, 58 }; 59 60 /*****************************************************************************/ 61 /* 62 * add a contiguous set of pages into a ramfs inode when it's truncated from 63 * size 0 on the assumption that it's going to be used for an mmap of shared 64 * memory 65 */ 66 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) 67 { 68 unsigned long npages, xpages, loop; 69 struct page *pages; 70 unsigned order; 71 void *data; 72 int ret; 73 74 /* make various checks */ 75 order = get_order(newsize); 76 if (unlikely(order >= MAX_ORDER)) 77 return -EFBIG; 78 79 ret = inode_newsize_ok(inode, newsize); 80 if (ret) 81 return ret; 82 83 i_size_write(inode, newsize); 84 85 /* allocate enough contiguous pages to be able to satisfy the 86 * request */ 87 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order); 88 if (!pages) 89 return -ENOMEM; 90 91 /* split the high-order page into an array of single pages */ 92 xpages = 1UL << order; 93 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; 94 95 split_page(pages, order); 96 97 /* trim off any pages we don't actually require */ 98 for (loop = npages; loop < xpages; loop++) 99 __free_page(pages + loop); 100 101 /* clear the memory we allocated */ 102 newsize = PAGE_SIZE * npages; 103 data = page_address(pages); 104 memset(data, 0, newsize); 105 106 /* attach all the pages to the inode's address space */ 107 for (loop = 0; loop < npages; loop++) { 108 struct page *page = pages + loop; 109 110 ret = add_to_page_cache_lru(page, inode->i_mapping, loop, 111 GFP_KERNEL); 112 if (ret < 0) 113 goto add_error; 114 115 /* prevent the page from being discarded on memory pressure */ 116 SetPageDirty(page); 117 SetPageUptodate(page); 118 119 unlock_page(page); 120 put_page(page); 121 } 122 123 return 0; 124 125 add_error: 126 while (loop < npages) 127 __free_page(pages + loop++); 128 return ret; 129 } 130 131 /*****************************************************************************/ 132 /* 133 * 134 */ 135 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 136 { 137 int ret; 138 139 /* assume a truncate from zero size is going to be for the purposes of 140 * shared mmap */ 141 if (size == 0) { 142 if (unlikely(newsize >> 32)) 143 return -EFBIG; 144 145 return ramfs_nommu_expand_for_mapping(inode, newsize); 146 } 147 148 /* check that a decrease in size doesn't cut off any shared mappings */ 149 if (newsize < size) { 150 ret = nommu_shrink_inode_mappings(inode, size, newsize); 151 if (ret < 0) 152 return ret; 153 } 154 155 truncate_setsize(inode, newsize); 156 return 0; 157 } 158 159 /*****************************************************************************/ 160 /* 161 * handle a change of attributes 162 * - we're specifically interested in a change of size 163 */ 164 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 165 { 166 struct inode *inode = d_inode(dentry); 167 unsigned int old_ia_valid = ia->ia_valid; 168 int ret = 0; 169 170 /* POSIX UID/GID verification for setting inode attributes */ 171 ret = inode_change_ok(inode, ia); 172 if (ret) 173 return ret; 174 175 /* pick out size-changing events */ 176 if (ia->ia_valid & ATTR_SIZE) { 177 loff_t size = inode->i_size; 178 179 if (ia->ia_size != size) { 180 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 181 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 182 goto out; 183 } else { 184 /* we skipped the truncate but must still update 185 * timestamps 186 */ 187 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 188 } 189 } 190 191 setattr_copy(inode, ia); 192 out: 193 ia->ia_valid = old_ia_valid; 194 return ret; 195 } 196 197 /*****************************************************************************/ 198 /* 199 * try to determine where a shared mapping can be made 200 * - we require that: 201 * - the pages to be mapped must exist 202 * - the pages be physically contiguous in sequence 203 */ 204 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 205 unsigned long addr, unsigned long len, 206 unsigned long pgoff, unsigned long flags) 207 { 208 unsigned long maxpages, lpages, nr, loop, ret; 209 struct inode *inode = file_inode(file); 210 struct page **pages = NULL, **ptr, *page; 211 loff_t isize; 212 213 if (!(flags & MAP_SHARED)) 214 return addr; 215 216 /* the mapping mustn't extend beyond the EOF */ 217 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 218 isize = i_size_read(inode); 219 220 ret = -EINVAL; 221 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 222 if (pgoff >= maxpages) 223 goto out; 224 225 if (maxpages - pgoff < lpages) 226 goto out; 227 228 /* gang-find the pages */ 229 ret = -ENOMEM; 230 pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL); 231 if (!pages) 232 goto out_free; 233 234 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); 235 if (nr != lpages) 236 goto out_free_pages; /* leave if some pages were missing */ 237 238 /* check the pages for physical adjacency */ 239 ptr = pages; 240 page = *ptr++; 241 page++; 242 for (loop = lpages; loop > 1; loop--) 243 if (*ptr++ != page++) 244 goto out_free_pages; 245 246 /* okay - all conditions fulfilled */ 247 ret = (unsigned long) page_address(pages[0]); 248 249 out_free_pages: 250 ptr = pages; 251 for (loop = nr; loop > 0; loop--) 252 put_page(*ptr++); 253 out_free: 254 kfree(pages); 255 out: 256 return ret; 257 } 258 259 /*****************************************************************************/ 260 /* 261 * set up a mapping for shared memory segments 262 */ 263 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 264 { 265 if (!(vma->vm_flags & VM_SHARED)) 266 return -ENOSYS; 267 268 file_accessed(file); 269 vma->vm_ops = &generic_file_vm_ops; 270 return 0; 271 } 272