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/pagevec.h>
  22 #include <linux/mman.h>
  23
  24 #include <asm/uaccess.h>
  25 #include "internal.h"
  26
  27 static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
  28
  29 const struct address_space_operations ramfs_aops = {
  30         .readpage               = simple_readpage,
  31         .write_begin            = simple_write_begin,
  32         .write_end              = simple_write_end,
  33         .set_page_dirty         = __set_page_dirty_no_writeback,
  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         .splice_read            = generic_file_splice_read,
  45         .splice_write           = generic_file_splice_write,
  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 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_file(&lru_pvec);
 115
 116                 /* prevent the page from being discarded on memory pressure */
 117                 SetPageDirty(page);
 118
 119                 unlock_page(page);
 120         }
 121
 122         pagevec_lru_add_file(&lru_pvec);
 123         return 0;
 124
 125  fsize_exceeded:
 126         send_sig(SIGXFSZ, current, 0);
 127  too_big:
 128         return -EFBIG;
 129
 130  add_error:
 131         pagevec_lru_add_file(&lru_pvec);
 132         page_cache_release(pages + loop);
 133         for (loop++; loop < npages; loop++)
 134                 __free_page(pages + loop);
 135         return ret;
 136 }
 137
 138 /*****************************************************************************/
 139 /*
 140  * check that file shrinkage doesn't leave any VMAs dangling in midair
 141  */
 142 static int ramfs_nommu_check_mappings(struct inode *inode,
 143                                       size_t newsize, size_t size)
 144 {
 145         struct vm_area_struct *vma;
 146         struct prio_tree_iter iter;
 147
 148         /* search for VMAs that fall within the dead zone */
 149         vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
 150                               newsize >> PAGE_SHIFT,
 151                               (size + PAGE_SIZE - 1) >> PAGE_SHIFT
 152                               ) {
 153                 /* found one - only interested if it's shared out of the page
 154                  * cache */
 155                 if (vma->vm_flags & VM_SHARED)
 156                         return -ETXTBSY; /* not quite true, but near enough */
 157         }
 158
 159         return 0;
 160 }
 161
 162 /*****************************************************************************/
 163 /*
 164  *
 165  */
 166 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 167 {
 168         int ret;
 169
 170         /* assume a truncate from zero size is going to be for the purposes of
 171          * shared mmap */
 172         if (size == 0) {
 173                 if (unlikely(newsize >> 32))
 174                         return -EFBIG;
 175
 176                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 177         }
 178
 179         /* check that a decrease in size doesn't cut off any shared mappings */
 180         if (newsize < size) {
 181                 ret = ramfs_nommu_check_mappings(inode, newsize, size);
 182                 if (ret < 0)
 183                         return ret;
 184         }
 185
 186         ret = vmtruncate(inode, newsize);
 187
 188         return ret;
 189 }
 190
 191 /*****************************************************************************/
 192 /*
 193  * handle a change of attributes
 194  * - we're specifically interested in a change of size
 195  */
 196 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 197 {
 198         struct inode *inode = dentry->d_inode;
 199         unsigned int old_ia_valid = ia->ia_valid;
 200         int ret = 0;
 201
 202         /* POSIX UID/GID verification for setting inode attributes */
 203         ret = inode_change_ok(inode, ia);
 204         if (ret)
 205                 return ret;
 206
 207         /* pick out size-changing events */
 208         if (ia->ia_valid & ATTR_SIZE) {
 209                 loff_t size = i_size_read(inode);
 210                 if (ia->ia_size != size) {
 211                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 212                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 213                                 goto out;
 214                 } else {
 215                         /* we skipped the truncate but must still update
 216                          * timestamps
 217                          */
 218                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 219                 }
 220         }
 221
 222         ret = inode_setattr(inode, ia);
 223  out:
 224         ia->ia_valid = old_ia_valid;
 225         return ret;
 226 }
 227
 228 /*****************************************************************************/
 229 /*
 230  * try to determine where a shared mapping can be made
 231  * - we require that:
 232  *   - the pages to be mapped must exist
 233  *   - the pages be physically contiguous in sequence
 234  */
 235 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 236                                             unsigned long addr, unsigned long len,
 237                                             unsigned long pgoff, unsigned long flags)
 238 {
 239         unsigned long maxpages, lpages, nr, loop, ret;
 240         struct inode *inode = file->f_path.dentry->d_inode;
 241         struct page **pages = NULL, **ptr, *page;
 242         loff_t isize;
 243
 244         if (!(flags & MAP_SHARED))
 245                 return addr;
 246
 247         /* the mapping mustn't extend beyond the EOF */
 248         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 249         isize = i_size_read(inode);
 250
 251         ret = -EINVAL;
 252         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 253         if (pgoff >= maxpages)
 254                 goto out;
 255
 256         if (maxpages - pgoff < lpages)
 257                 goto out;
 258
 259         /* gang-find the pages */
 260         ret = -ENOMEM;
 261         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 262         if (!pages)
 263                 goto out_free;
 264
 265         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 266         if (nr != lpages)
 267                 goto out_free_pages; /* leave if some pages were missing */
 268
 269         /* check the pages for physical adjacency */
 270         ptr = pages;
 271         page = *ptr++;
 272         page++;
 273         for (loop = lpages; loop > 1; loop--)
 274                 if (*ptr++ != page++)
 275                         goto out_free_pages;
 276
 277         /* okay - all conditions fulfilled */
 278         ret = (unsigned long) page_address(pages[0]);
 279
 280 out_free_pages:
 281         ptr = pages;
 282         for (loop = nr; loop > 0; loop--)
 283                 put_page(*ptr++);
 284 out_free:
 285         kfree(pages);
 286 out:
 287         return ret;
 288 }
 289
 290 /*****************************************************************************/
 291 /*
 292  * set up a mapping for shared memory segments
 293  */
 294 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 295 {
 296         if (!(vma->vm_flags & VM_SHARED))
 297                 return -ENOSYS;
 298
 299         file_accessed(file);
 300         vma->vm_ops = &generic_file_vm_ops;
 301         return 0;
 302 }