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/smp_lock.h>
  20 #include <linux/backing-dev.h>
  21 #include <linux/ramfs.h>
  22 #include <linux/quotaops.h>
  23 #include <linux/pagevec.h>
  24 #include <linux/mman.h>
  25
  26 #include <asm/uaccess.h>
  27 #include "internal.h"
  28
  29 static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
  30
  31 const struct address_space_operations ramfs_aops = {
  32         .readpage               = simple_readpage,
  33         .prepare_write          = simple_prepare_write,
  34         .commit_write           = simple_commit_write,
  35         .set_page_dirty = __set_page_dirty_nobuffers,
  36 };
  37
  38 const struct file_operations ramfs_file_operations = {
  39         .mmap                   = ramfs_nommu_mmap,
  40         .get_unmapped_area      = ramfs_nommu_get_unmapped_area,
  41         .read                   = do_sync_read,
  42         .aio_read               = generic_file_aio_read,
  43         .write                  = do_sync_write,
  44         .aio_write              = generic_file_aio_write,
  45         .fsync                  = simple_sync_file,
  46         .sendfile               = generic_file_sendfile,
  47         .llseek                 = generic_file_llseek,
  48 };
  49
  50 struct inode_operations ramfs_file_inode_operations = {
  51         .setattr                = ramfs_nommu_setattr,
  52         .getattr                = simple_getattr,
  53 };
  54
  55 /*****************************************************************************/
  56 /*
  57  * add a contiguous set of pages into a ramfs inode when it's truncated from
  58  * size 0 on the assumption that it's going to be used for an mmap of shared
  59  * memory
  60  */
  61 static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
  62 {
  63         struct pagevec lru_pvec;
  64         unsigned long npages, xpages, loop, limit;
  65         struct page *pages;
  66         unsigned order;
  67         void *data;
  68         int ret;
  69
  70         /* make various checks */
  71         order = get_order(newsize);
  72         if (unlikely(order >= MAX_ORDER))
  73                 goto too_big;
  74
  75         limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
  76         if (limit != RLIM_INFINITY && newsize > limit)
  77                 goto fsize_exceeded;
  78
  79         if (newsize > inode->i_sb->s_maxbytes)
  80                 goto too_big;
  81
  82         i_size_write(inode, newsize);
  83
  84         /* allocate enough contiguous pages to be able to satisfy the
  85          * request */
  86         pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
  87         if (!pages)
  88                 return -ENOMEM;
  89
  90         /* split the high-order page into an array of single pages */
  91         xpages = 1UL << order;
  92         npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  93
  94         split_page(pages, order);
  95
  96         /* trim off any pages we don't actually require */
  97         for (loop = npages; loop < xpages; loop++)
  98                 __free_page(pages + loop);
  99
 100         /* clear the memory we allocated */
 101         newsize = PAGE_SIZE * npages;
 102         data = page_address(pages);
 103         memset(data, 0, newsize);
 104
 105         /* attach all the pages to the inode's address space */
 106         pagevec_init(&lru_pvec, 0);
 107         for (loop = 0; loop < npages; loop++) {
 108                 struct page *page = pages + loop;
 109
 110                 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
 111                 if (ret < 0)
 112                         goto add_error;
 113
 114                 if (!pagevec_add(&lru_pvec, page))
 115                         __pagevec_lru_add(&lru_pvec);
 116
 117                 unlock_page(page);
 118         }
 119
 120         pagevec_lru_add(&lru_pvec);
 121         return 0;
 122
 123  fsize_exceeded:
 124         send_sig(SIGXFSZ, current, 0);
 125  too_big:
 126         return -EFBIG;
 127
 128  add_error:
 129         page_cache_release(pages + loop);
 130         for (loop++; loop < npages; loop++)
 131                 __free_page(pages + loop);
 132         return ret;
 133 }
 134
 135 /*****************************************************************************/
 136 /*
 137  * check that file shrinkage doesn't leave any VMAs dangling in midair
 138  */
 139 static int ramfs_nommu_check_mappings(struct inode *inode,
 140                                       size_t newsize, size_t size)
 141 {
 142         struct vm_area_struct *vma;
 143         struct prio_tree_iter iter;
 144
 145         /* search for VMAs that fall within the dead zone */
 146         vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
 147                               newsize >> PAGE_SHIFT,
 148                               (size + PAGE_SIZE - 1) >> PAGE_SHIFT
 149                               ) {
 150                 /* found one - only interested if it's shared out of the page
 151                  * cache */
 152                 if (vma->vm_flags & VM_SHARED)
 153                         return -ETXTBSY; /* not quite true, but near enough */
 154         }
 155
 156         return 0;
 157 }
 158
 159 /*****************************************************************************/
 160 /*
 161  *
 162  */
 163 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 164 {
 165         int ret;
 166
 167         /* assume a truncate from zero size is going to be for the purposes of
 168          * shared mmap */
 169         if (size == 0) {
 170                 if (unlikely(newsize >> 32))
 171                         return -EFBIG;
 172
 173                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 174         }
 175
 176         /* check that a decrease in size doesn't cut off any shared mappings */
 177         if (newsize < size) {
 178                 ret = ramfs_nommu_check_mappings(inode, newsize, size);
 179                 if (ret < 0)
 180                         return ret;
 181         }
 182
 183         ret = vmtruncate(inode, size);
 184
 185         return ret;
 186 }
 187
 188 /*****************************************************************************/
 189 /*
 190  * handle a change of attributes
 191  * - we're specifically interested in a change of size
 192  */
 193 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 194 {
 195         struct inode *inode = dentry->d_inode;
 196         unsigned int old_ia_valid = ia->ia_valid;
 197         int ret = 0;
 198
 199         /* by providing our own setattr() method, we skip this quotaism */
 200         if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
 201             (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
 202                 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
 203
 204         /* pick out size-changing events */
 205         if (ia->ia_valid & ATTR_SIZE) {
 206                 loff_t size = i_size_read(inode);
 207                 if (ia->ia_size != size) {
 208                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 209                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 210                                 goto out;
 211                 } else {
 212                         /* we skipped the truncate but must still update
 213                          * timestamps
 214                          */
 215                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 216                 }
 217         }
 218
 219         ret = inode_setattr(inode, ia);
 220  out:
 221         ia->ia_valid = old_ia_valid;
 222         return ret;
 223 }
 224
 225 /*****************************************************************************/
 226 /*
 227  * try to determine where a shared mapping can be made
 228  * - we require that:
 229  *   - the pages to be mapped must exist
 230  *   - the pages be physically contiguous in sequence
 231  */
 232 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 233                                             unsigned long addr, unsigned long len,
 234                                             unsigned long pgoff, unsigned long flags)
 235 {
 236         unsigned long maxpages, lpages, nr, loop, ret;
 237         struct inode *inode = file->f_path.dentry->d_inode;
 238         struct page **pages = NULL, **ptr, *page;
 239         loff_t isize;
 240
 241         if (!(flags & MAP_SHARED))
 242                 return addr;
 243
 244         /* the mapping mustn't extend beyond the EOF */
 245         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 246         isize = i_size_read(inode);
 247
 248         ret = -EINVAL;
 249         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 250         if (pgoff >= maxpages)
 251                 goto out;
 252
 253         if (maxpages - pgoff < lpages)
 254                 goto out;
 255
 256         /* gang-find the pages */
 257         ret = -ENOMEM;
 258         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 259         if (!pages)
 260                 goto out;
 261
 262         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 263         if (nr != lpages)
 264                 goto out; /* leave if some pages were missing */
 265
 266         /* check the pages for physical adjacency */
 267         ptr = pages;
 268         page = *ptr++;
 269         page++;
 270         for (loop = lpages; loop > 1; loop--)
 271                 if (*ptr++ != page++)
 272                         goto out;
 273
 274         /* okay - all conditions fulfilled */
 275         ret = (unsigned long) page_address(pages[0]);
 276
 277  out:
 278         if (pages) {
 279                 ptr = pages;
 280                 for (loop = lpages; loop > 0; loop--)
 281                         put_page(*ptr++);
 282                 kfree(pages);
 283         }
 284
 285         return ret;
 286 }
 287
 288 /*****************************************************************************/
 289 /*
 290  * set up a mapping for shared memory segments
 291  */
 292 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 293 {
 294         return vma->vm_flags & VM_SHARED ? 0 : -ENOSYS;
 295 }