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/pagemap.h> 15 #include <linux/highmem.h> 16 #include <linux/init.h> 17 #include <linux/string.h> 18 #include <linux/smp_lock.h> 19 #include <linux/backing-dev.h> 20 #include <linux/ramfs.h> 21 #include <linux/quotaops.h> 22 #include <linux/pagevec.h> 23 #include <linux/mman.h> 24 25 #include <asm/uaccess.h> 26 #include "internal.h" 27 28 static int ramfs_nommu_setattr(struct dentry *, struct iattr *); 29 30 struct address_space_operations ramfs_aops = { 31 .readpage = simple_readpage, 32 .prepare_write = simple_prepare_write, 33 .commit_write = simple_commit_write 34 }; 35 36 const struct file_operations ramfs_file_operations = { 37 .mmap = ramfs_nommu_mmap, 38 .get_unmapped_area = ramfs_nommu_get_unmapped_area, 39 .read = generic_file_read, 40 .write = generic_file_write, 41 .fsync = simple_sync_file, 42 .sendfile = generic_file_sendfile, 43 .llseek = generic_file_llseek, 44 }; 45 46 struct inode_operations ramfs_file_inode_operations = { 47 .setattr = ramfs_nommu_setattr, 48 .getattr = simple_getattr, 49 }; 50 51 /*****************************************************************************/ 52 /* 53 * add a contiguous set of pages into a ramfs inode when it's truncated from 54 * size 0 on the assumption that it's going to be used for an mmap of shared 55 * memory 56 */ 57 static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) 58 { 59 struct pagevec lru_pvec; 60 unsigned long npages, xpages, loop, limit; 61 struct page *pages; 62 unsigned order; 63 void *data; 64 int ret; 65 66 /* make various checks */ 67 order = get_order(newsize); 68 if (unlikely(order >= MAX_ORDER)) 69 goto too_big; 70 71 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; 72 if (limit != RLIM_INFINITY && newsize > limit) 73 goto fsize_exceeded; 74 75 if (newsize > inode->i_sb->s_maxbytes) 76 goto too_big; 77 78 i_size_write(inode, newsize); 79 80 /* allocate enough contiguous pages to be able to satisfy the 81 * request */ 82 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order); 83 if (!pages) 84 return -ENOMEM; 85 86 /* split the high-order page into an array of single pages */ 87 xpages = 1UL << order; 88 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; 89 90 split_page(pages, order); 91 92 /* trim off any pages we don't actually require */ 93 for (loop = npages; loop < xpages; loop++) 94 __free_page(pages + loop); 95 96 /* clear the memory we allocated */ 97 newsize = PAGE_SIZE * npages; 98 data = page_address(pages); 99 memset(data, 0, newsize); 100 101 /* attach all the pages to the inode's address space */ 102 pagevec_init(&lru_pvec, 0); 103 for (loop = 0; loop < npages; loop++) { 104 struct page *page = pages + loop; 105 106 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL); 107 if (ret < 0) 108 goto add_error; 109 110 if (!pagevec_add(&lru_pvec, page)) 111 __pagevec_lru_add(&lru_pvec); 112 113 unlock_page(page); 114 } 115 116 pagevec_lru_add(&lru_pvec); 117 return 0; 118 119 fsize_exceeded: 120 send_sig(SIGXFSZ, current, 0); 121 too_big: 122 return -EFBIG; 123 124 add_error: 125 page_cache_release(pages + loop); 126 for (loop++; loop < npages; loop++) 127 __free_page(pages + loop); 128 return ret; 129 } 130 131 /*****************************************************************************/ 132 /* 133 * check that file shrinkage doesn't leave any VMAs dangling in midair 134 */ 135 static int ramfs_nommu_check_mappings(struct inode *inode, 136 size_t newsize, size_t size) 137 { 138 struct vm_area_struct *vma; 139 struct prio_tree_iter iter; 140 141 /* search for VMAs that fall within the dead zone */ 142 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, 143 newsize >> PAGE_SHIFT, 144 (size + PAGE_SIZE - 1) >> PAGE_SHIFT 145 ) { 146 /* found one - only interested if it's shared out of the page 147 * cache */ 148 if (vma->vm_flags & VM_SHARED) 149 return -ETXTBSY; /* not quite true, but near enough */ 150 } 151 152 return 0; 153 } 154 155 /*****************************************************************************/ 156 /* 157 * 158 */ 159 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 160 { 161 int ret; 162 163 /* assume a truncate from zero size is going to be for the purposes of 164 * shared mmap */ 165 if (size == 0) { 166 if (unlikely(newsize >> 32)) 167 return -EFBIG; 168 169 return ramfs_nommu_expand_for_mapping(inode, newsize); 170 } 171 172 /* check that a decrease in size doesn't cut off any shared mappings */ 173 if (newsize < size) { 174 ret = ramfs_nommu_check_mappings(inode, newsize, size); 175 if (ret < 0) 176 return ret; 177 } 178 179 ret = vmtruncate(inode, size); 180 181 return ret; 182 } 183 184 /*****************************************************************************/ 185 /* 186 * handle a change of attributes 187 * - we're specifically interested in a change of size 188 */ 189 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 190 { 191 struct inode *inode = dentry->d_inode; 192 unsigned int old_ia_valid = ia->ia_valid; 193 int ret = 0; 194 195 /* by providing our own setattr() method, we skip this quotaism */ 196 if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) || 197 (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid)) 198 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0; 199 200 /* pick out size-changing events */ 201 if (ia->ia_valid & ATTR_SIZE) { 202 loff_t size = i_size_read(inode); 203 if (ia->ia_size != size) { 204 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 205 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 206 goto out; 207 } else { 208 /* we skipped the truncate but must still update 209 * timestamps 210 */ 211 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 212 } 213 } 214 215 ret = inode_setattr(inode, ia); 216 out: 217 ia->ia_valid = old_ia_valid; 218 return ret; 219 } 220 221 /*****************************************************************************/ 222 /* 223 * try to determine where a shared mapping can be made 224 * - we require that: 225 * - the pages to be mapped must exist 226 * - the pages be physically contiguous in sequence 227 */ 228 unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 229 unsigned long addr, unsigned long len, 230 unsigned long pgoff, unsigned long flags) 231 { 232 unsigned long maxpages, lpages, nr, loop, ret; 233 struct inode *inode = file->f_dentry->d_inode; 234 struct page **pages = NULL, **ptr, *page; 235 loff_t isize; 236 237 if (!(flags & MAP_SHARED)) 238 return addr; 239 240 /* the mapping mustn't extend beyond the EOF */ 241 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 242 isize = i_size_read(inode); 243 244 ret = -EINVAL; 245 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 246 if (pgoff >= maxpages) 247 goto out; 248 249 if (maxpages - pgoff < lpages) 250 goto out; 251 252 /* gang-find the pages */ 253 ret = -ENOMEM; 254 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); 255 if (!pages) 256 goto out; 257 258 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); 259 if (nr != lpages) 260 goto out; /* leave if some pages were missing */ 261 262 /* check the pages for physical adjacency */ 263 ptr = pages; 264 page = *ptr++; 265 page++; 266 for (loop = lpages; loop > 1; loop--) 267 if (*ptr++ != page++) 268 goto out; 269 270 /* okay - all conditions fulfilled */ 271 ret = (unsigned long) page_address(pages[0]); 272 273 out: 274 if (pages) { 275 ptr = pages; 276 for (loop = lpages; loop > 0; loop--) 277 put_page(*ptr++); 278 kfree(pages); 279 } 280 281 return ret; 282 } 283 284 /*****************************************************************************/ 285 /* 286 * set up a mapping 287 */ 288 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 289 { 290 return 0; 291 } 292