fs/ramfs/file-nommu.c

   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         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 }