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/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/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         .write_begin            = simple_write_begin,
  33         .write_end              = simple_write_end,
  34         .set_page_dirty         = __set_page_dirty_no_writeback,
  35 };
  36
  37 const struct file_operations ramfs_file_operations = {
  38         .mmap                   = ramfs_nommu_mmap,
  39         .get_unmapped_area      = ramfs_nommu_get_unmapped_area,
  40         .read                   = do_sync_read,
  41         .aio_read               = generic_file_aio_read,
  42         .write                  = do_sync_write,
  43         .aio_write              = generic_file_aio_write,
  44         .fsync                  = simple_sync_file,
  45         .splice_read            = generic_file_splice_read,
  46         .llseek                 = generic_file_llseek,
  47 };
  48
  49 const struct inode_operations ramfs_file_inode_operations = {
  50         .setattr                = ramfs_nommu_setattr,
  51         .getattr                = simple_getattr,
  52 };
  53
  54 /*****************************************************************************/
  55 /*
  56  * add a contiguous set of pages into a ramfs inode when it's truncated from
  57  * size 0 on the assumption that it's going to be used for an mmap of shared
  58  * memory
  59  */
  60 static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
  61 {
  62         struct pagevec lru_pvec;
  63         unsigned long npages, xpages, loop, limit;
  64         struct page *pages;
  65         unsigned order;
  66         void *data;
  67         int ret;
  68
  69         /* make various checks */
  70         order = get_order(newsize);
  71         if (unlikely(order >= MAX_ORDER))
  72                 goto too_big;
  73
  74         limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
  75         if (limit != RLIM_INFINITY && newsize > limit)
  76                 goto fsize_exceeded;
  77
  78         if (newsize > inode->i_sb->s_maxbytes)
  79                 goto too_big;
  80
  81         i_size_write(inode, newsize);
  82
  83         /* allocate enough contiguous pages to be able to satisfy the
  84          * request */
  85         pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
  86         if (!pages)
  87                 return -ENOMEM;
  88
  89         /* split the high-order page into an array of single pages */
  90         xpages = 1UL << order;
  91         npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  92
  93         split_page(pages, order);
  94
  95         /* trim off any pages we don't actually require */
  96         for (loop = npages; loop < xpages; loop++)
  97                 __free_page(pages + loop);
  98
  99         /* clear the memory we allocated */
 100         newsize = PAGE_SIZE * npages;
 101         data = page_address(pages);
 102         memset(data, 0, newsize);
 103
 104         /* attach all the pages to the inode's address space */
 105         pagevec_init(&lru_pvec, 0);
 106         for (loop = 0; loop < npages; loop++) {
 107                 struct page *page = pages + loop;
 108
 109                 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
 110                 if (ret < 0)
 111                         goto add_error;
 112
 113                 if (!pagevec_add(&lru_pvec, page))
 114                         __pagevec_lru_add(&lru_pvec);
 115
 116                 unlock_page(page);
 117         }
 118
 119         pagevec_lru_add(&lru_pvec);
 120         return 0;
 121
 122  fsize_exceeded:
 123         send_sig(SIGXFSZ, current, 0);
 124  too_big:
 125         return -EFBIG;
 126
 127  add_error:
 128         page_cache_release(pages + loop);
 129         for (loop++; loop < npages; loop++)
 130                 __free_page(pages + loop);
 131         return ret;
 132 }
 133
 134 /*****************************************************************************/
 135 /*
 136  * check that file shrinkage doesn't leave any VMAs dangling in midair
 137  */
 138 static int ramfs_nommu_check_mappings(struct inode *inode,
 139                                       size_t newsize, size_t size)
 140 {
 141         struct vm_area_struct *vma;
 142         struct prio_tree_iter iter;
 143
 144         /* search for VMAs that fall within the dead zone */
 145         vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
 146                               newsize >> PAGE_SHIFT,
 147                               (size + PAGE_SIZE - 1) >> PAGE_SHIFT
 148                               ) {
 149                 /* found one - only interested if it's shared out of the page
 150                  * cache */
 151                 if (vma->vm_flags & VM_SHARED)
 152                         return -ETXTBSY; /* not quite true, but near enough */
 153         }
 154
 155         return 0;
 156 }
 157
 158 /*****************************************************************************/
 159 /*
 160  *
 161  */
 162 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 163 {
 164         int ret;
 165
 166         /* assume a truncate from zero size is going to be for the purposes of
 167          * shared mmap */
 168         if (size == 0) {
 169                 if (unlikely(newsize >> 32))
 170                         return -EFBIG;
 171
 172                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 173         }
 174
 175         /* check that a decrease in size doesn't cut off any shared mappings */
 176         if (newsize < size) {
 177                 ret = ramfs_nommu_check_mappings(inode, newsize, size);
 178                 if (ret < 0)
 179                         return ret;
 180         }
 181
 182         ret = vmtruncate(inode, newsize);
 183
 184         return ret;
 185 }
 186
 187 /*****************************************************************************/
 188 /*
 189  * handle a change of attributes
 190  * - we're specifically interested in a change of size
 191  */
 192 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 193 {
 194         struct inode *inode = dentry->d_inode;
 195         unsigned int old_ia_valid = ia->ia_valid;
 196         int ret = 0;
 197
 198         /* POSIX UID/GID verification for setting inode attributes */
 199         ret = inode_change_ok(inode, ia);
 200         if (ret)
 201                 return ret;
 202
 203         /* by providing our own setattr() method, we skip this quotaism */
 204         if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
 205             (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
 206                 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
 207
 208         /* pick out size-changing events */
 209         if (ia->ia_valid & ATTR_SIZE) {
 210                 loff_t size = i_size_read(inode);
 211                 if (ia->ia_size != size) {
 212                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 213                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 214                                 goto out;
 215                 } else {
 216                         /* we skipped the truncate but must still update
 217                          * timestamps
 218                          */
 219                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 220                 }
 221         }
 222
 223         ret = inode_setattr(inode, ia);
 224  out:
 225         ia->ia_valid = old_ia_valid;
 226         return ret;
 227 }
 228
 229 /*****************************************************************************/
 230 /*
 231  * try to determine where a shared mapping can be made
 232  * - we require that:
 233  *   - the pages to be mapped must exist
 234  *   - the pages be physically contiguous in sequence
 235  */
 236 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 237                                             unsigned long addr, unsigned long len,
 238                                             unsigned long pgoff, unsigned long flags)
 239 {
 240         unsigned long maxpages, lpages, nr, loop, ret;
 241         struct inode *inode = file->f_path.dentry->d_inode;
 242         struct page **pages = NULL, **ptr, *page;
 243         loff_t isize;
 244
 245         if (!(flags & MAP_SHARED))
 246                 return addr;
 247
 248         /* the mapping mustn't extend beyond the EOF */
 249         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 250         isize = i_size_read(inode);
 251
 252         ret = -EINVAL;
 253         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 254         if (pgoff >= maxpages)
 255                 goto out;
 256
 257         if (maxpages - pgoff < lpages)
 258                 goto out;
 259
 260         /* gang-find the pages */
 261         ret = -ENOMEM;
 262         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 263         if (!pages)
 264                 goto out;
 265
 266         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 267         if (nr != lpages)
 268                 goto out; /* leave if some pages were missing */
 269
 270         /* check the pages for physical adjacency */
 271         ptr = pages;
 272         page = *ptr++;
 273         page++;
 274         for (loop = lpages; loop > 1; loop--)
 275                 if (*ptr++ != page++)
 276                         goto out;
 277
 278         /* okay - all conditions fulfilled */
 279         ret = (unsigned long) page_address(pages[0]);
 280
 281  out:
 282         if (pages) {
 283                 ptr = pages;
 284                 for (loop = lpages; loop > 0; loop--)
 285                         put_page(*ptr++);
 286                 kfree(pages);
 287         }
 288
 289         return ret;
 290 }
 291
 292 /*****************************************************************************/
 293 /*
 294  * set up a mapping for shared memory segments
 295  */
 296 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 297 {
 298         if (!(vma->vm_flags & VM_SHARED))
 299                 return -ENOSYS;
 300
 301         file_accessed(file);
 302         vma->vm_ops = &generic_file_vm_ops;
 303         return 0;
 304 }