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 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 for (loop = 0; loop < npages; loop++) 91 set_page_count(pages + loop, 1); 92 93 /* trim off any pages we don't actually require */ 94 for (loop = npages; loop < xpages; loop++) 95 __free_page(pages + loop); 96 97 /* clear the memory we allocated */ 98 newsize = PAGE_SIZE * npages; 99 data = page_address(pages); 100 memset(data, 0, newsize); 101 102 /* attach all the pages to the inode's address space */ 103 pagevec_init(&lru_pvec, 0); 104 for (loop = 0; loop < npages; loop++) { 105 struct page *page = pages + loop; 106 107 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL); 108 if (ret < 0) 109 goto add_error; 110 111 if (!pagevec_add(&lru_pvec, page)) 112 __pagevec_lru_add(&lru_pvec); 113 114 unlock_page(page); 115 } 116 117 pagevec_lru_add(&lru_pvec); 118 return 0; 119 120 fsize_exceeded: 121 send_sig(SIGXFSZ, current, 0); 122 too_big: 123 return -EFBIG; 124 125 add_error: 126 page_cache_release(pages + loop); 127 for (loop++; loop < npages; loop++) 128 __free_page(pages + loop); 129 return ret; 130 } 131 132 /*****************************************************************************/ 133 /* 134 * check that file shrinkage doesn't leave any VMAs dangling in midair 135 */ 136 static int ramfs_nommu_check_mappings(struct inode *inode, 137 size_t newsize, size_t size) 138 { 139 struct vm_area_struct *vma; 140 struct prio_tree_iter iter; 141 142 /* search for VMAs that fall within the dead zone */ 143 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, 144 newsize >> PAGE_SHIFT, 145 (size + PAGE_SIZE - 1) >> PAGE_SHIFT 146 ) { 147 /* found one - only interested if it's shared out of the page 148 * cache */ 149 if (vma->vm_flags & VM_SHARED) 150 return -ETXTBSY; /* not quite true, but near enough */ 151 } 152 153 return 0; 154 } 155 156 /*****************************************************************************/ 157 /* 158 * 159 */ 160 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 161 { 162 int ret; 163 164 /* assume a truncate from zero size is going to be for the purposes of 165 * shared mmap */ 166 if (size == 0) { 167 if (unlikely(newsize >> 32)) 168 return -EFBIG; 169 170 return ramfs_nommu_expand_for_mapping(inode, newsize); 171 } 172 173 /* check that a decrease in size doesn't cut off any shared mappings */ 174 if (newsize < size) { 175 ret = ramfs_nommu_check_mappings(inode, newsize, size); 176 if (ret < 0) 177 return ret; 178 } 179 180 ret = vmtruncate(inode, size); 181 182 return ret; 183 } 184 185 /*****************************************************************************/ 186 /* 187 * handle a change of attributes 188 * - we're specifically interested in a change of size 189 */ 190 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 191 { 192 struct inode *inode = dentry->d_inode; 193 unsigned int old_ia_valid = ia->ia_valid; 194 int ret = 0; 195 196 /* by providing our own setattr() method, we skip this quotaism */ 197 if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) || 198 (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid)) 199 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0; 200 201 /* pick out size-changing events */ 202 if (ia->ia_valid & ATTR_SIZE) { 203 loff_t size = i_size_read(inode); 204 if (ia->ia_size != size) { 205 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 206 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 207 goto out; 208 } else { 209 /* we skipped the truncate but must still update 210 * timestamps 211 */ 212 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 213 } 214 } 215 216 ret = inode_setattr(inode, ia); 217 out: 218 ia->ia_valid = old_ia_valid; 219 return ret; 220 } 221 222 /*****************************************************************************/ 223 /* 224 * try to determine where a shared mapping can be made 225 * - we require that: 226 * - the pages to be mapped must exist 227 * - the pages be physically contiguous in sequence 228 */ 229 unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 230 unsigned long addr, unsigned long len, 231 unsigned long pgoff, unsigned long flags) 232 { 233 unsigned long maxpages, lpages, nr, loop, ret; 234 struct inode *inode = file->f_dentry->d_inode; 235 struct page **pages = NULL, **ptr, *page; 236 loff_t isize; 237 238 if (!(flags & MAP_SHARED)) 239 return addr; 240 241 /* the mapping mustn't extend beyond the EOF */ 242 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 243 isize = i_size_read(inode); 244 245 ret = -EINVAL; 246 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 247 if (pgoff >= maxpages) 248 goto out; 249 250 if (maxpages - pgoff < lpages) 251 goto out; 252 253 /* gang-find the pages */ 254 ret = -ENOMEM; 255 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); 256 if (!pages) 257 goto out; 258 259 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); 260 if (nr != lpages) 261 goto out; /* leave if some pages were missing */ 262 263 /* check the pages for physical adjacency */ 264 ptr = pages; 265 page = *ptr++; 266 page++; 267 for (loop = lpages; loop > 1; loop--) 268 if (*ptr++ != page++) 269 goto out; 270 271 /* okay - all conditions fulfilled */ 272 ret = (unsigned long) page_address(pages[0]); 273 274 out: 275 if (pages) { 276 ptr = pages; 277 for (loop = lpages; loop > 0; loop--) 278 put_page(*ptr++); 279 kfree(pages); 280 } 281 282 return ret; 283 } 284 285 /*****************************************************************************/ 286 /* 287 * set up a mapping 288 */ 289 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 290 { 291 return 0; 292 } 293