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 const 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                   = do_sync_read,
  40         .aio_read               = generic_file_aio_read,
  41         .write                  = do_sync_write,
  42         .aio_write              = generic_file_aio_write,
  43         .fsync                  = simple_sync_file,
  44         .sendfile               = generic_file_sendfile,
  45         .llseek                 = generic_file_llseek,
  46 };
  47
  48 struct inode_operations ramfs_file_inode_operations = {
  49         .setattr                = ramfs_nommu_setattr,
  50         .getattr                = simple_getattr,
  51 };
  52
  53 /*****************************************************************************/
  54 /*
  55  * add a contiguous set of pages into a ramfs inode when it's truncated from
  56  * size 0 on the assumption that it's going to be used for an mmap of shared
  57  * memory
  58  */
  59 static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
  60 {
  61         struct pagevec lru_pvec;
  62         unsigned long npages, xpages, loop, limit;
  63         struct page *pages;
  64         unsigned order;
  65         void *data;
  66         int ret;
  67
  68         /* make various checks */
  69         order = get_order(newsize);
  70         if (unlikely(order >= MAX_ORDER))
  71                 goto too_big;
  72
  73         limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
  74         if (limit != RLIM_INFINITY && newsize > limit)
  75                 goto fsize_exceeded;
  76
  77         if (newsize > inode->i_sb->s_maxbytes)
  78                 goto too_big;
  79
  80         i_size_write(inode, newsize);
  81
  82         /* allocate enough contiguous pages to be able to satisfy the
  83          * request */
  84         pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), 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         pagevec_init(&lru_pvec, 0);
 105         for (loop = 0; loop < npages; loop++) {
 106                 struct page *page = pages + loop;
 107
 108                 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
 109                 if (ret < 0)
 110                         goto add_error;
 111
 112                 if (!pagevec_add(&lru_pvec, page))
 113                         __pagevec_lru_add(&lru_pvec);
 114
 115                 unlock_page(page);
 116         }
 117
 118         pagevec_lru_add(&lru_pvec);
 119         return 0;
 120
 121  fsize_exceeded:
 122         send_sig(SIGXFSZ, current, 0);
 123  too_big:
 124         return -EFBIG;
 125
 126  add_error:
 127         page_cache_release(pages + loop);
 128         for (loop++; loop < npages; loop++)
 129                 __free_page(pages + loop);
 130         return ret;
 131 }
 132
 133 /*****************************************************************************/
 134 /*
 135  * check that file shrinkage doesn't leave any VMAs dangling in midair
 136  */
 137 static int ramfs_nommu_check_mappings(struct inode *inode,
 138                                       size_t newsize, size_t size)
 139 {
 140         struct vm_area_struct *vma;
 141         struct prio_tree_iter iter;
 142
 143         /* search for VMAs that fall within the dead zone */
 144         vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
 145                               newsize >> PAGE_SHIFT,
 146                               (size + PAGE_SIZE - 1) >> PAGE_SHIFT
 147                               ) {
 148                 /* found one - only interested if it's shared out of the page
 149                  * cache */
 150                 if (vma->vm_flags & VM_SHARED)
 151                         return -ETXTBSY; /* not quite true, but near enough */
 152         }
 153
 154         return 0;
 155 }
 156
 157 /*****************************************************************************/
 158 /*
 159  *
 160  */
 161 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 162 {
 163         int ret;
 164
 165         /* assume a truncate from zero size is going to be for the purposes of
 166          * shared mmap */
 167         if (size == 0) {
 168                 if (unlikely(newsize >> 32))
 169                         return -EFBIG;
 170
 171                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 172         }
 173
 174         /* check that a decrease in size doesn't cut off any shared mappings */
 175         if (newsize < size) {
 176                 ret = ramfs_nommu_check_mappings(inode, newsize, size);
 177                 if (ret < 0)
 178                         return ret;
 179         }
 180
 181         ret = vmtruncate(inode, size);
 182
 183         return ret;
 184 }
 185
 186 /*****************************************************************************/
 187 /*
 188  * handle a change of attributes
 189  * - we're specifically interested in a change of size
 190  */
 191 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 192 {
 193         struct inode *inode = dentry->d_inode;
 194         unsigned int old_ia_valid = ia->ia_valid;
 195         int ret = 0;
 196
 197         /* by providing our own setattr() method, we skip this quotaism */
 198         if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
 199             (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
 200                 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
 201
 202         /* pick out size-changing events */
 203         if (ia->ia_valid & ATTR_SIZE) {
 204                 loff_t size = i_size_read(inode);
 205                 if (ia->ia_size != size) {
 206                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 207                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 208                                 goto out;
 209                 } else {
 210                         /* we skipped the truncate but must still update
 211                          * timestamps
 212                          */
 213                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 214                 }
 215         }
 216
 217         ret = inode_setattr(inode, ia);
 218  out:
 219         ia->ia_valid = old_ia_valid;
 220         return ret;
 221 }
 222
 223 /*****************************************************************************/
 224 /*
 225  * try to determine where a shared mapping can be made
 226  * - we require that:
 227  *   - the pages to be mapped must exist
 228  *   - the pages be physically contiguous in sequence
 229  */
 230 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 231                                             unsigned long addr, unsigned long len,
 232                                             unsigned long pgoff, unsigned long flags)
 233 {
 234         unsigned long maxpages, lpages, nr, loop, ret;
 235         struct inode *inode = file->f_dentry->d_inode;
 236         struct page **pages = NULL, **ptr, *page;
 237         loff_t isize;
 238
 239         if (!(flags & MAP_SHARED))
 240                 return addr;
 241
 242         /* the mapping mustn't extend beyond the EOF */
 243         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 244         isize = i_size_read(inode);
 245
 246         ret = -EINVAL;
 247         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 248         if (pgoff >= maxpages)
 249                 goto out;
 250
 251         if (maxpages - pgoff < lpages)
 252                 goto out;
 253
 254         /* gang-find the pages */
 255         ret = -ENOMEM;
 256         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 257         if (!pages)
 258                 goto out;
 259
 260         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 261         if (nr != lpages)
 262                 goto out; /* leave if some pages were missing */
 263
 264         /* check the pages for physical adjacency */
 265         ptr = pages;
 266         page = *ptr++;
 267         page++;
 268         for (loop = lpages; loop > 1; loop--)
 269                 if (*ptr++ != page++)
 270                         goto out;
 271
 272         /* okay - all conditions fulfilled */
 273         ret = (unsigned long) page_address(pages[0]);
 274
 275  out:
 276         if (pages) {
 277                 ptr = pages;
 278                 for (loop = lpages; loop > 0; loop--)
 279                         put_page(*ptr++);
 280                 kfree(pages);
 281         }
 282
 283         return ret;
 284 }
 285
 286 /*****************************************************************************/
 287 /*
 288  * set up a mapping for shared memory segments
 289  */
 290 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 291 {
 292         return vma->vm_flags & VM_SHARED ? 0 : -ENOSYS;
 293 }