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 #include <linux/sched.h>
  24 #include <linux/slab.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         .write_begin            = simple_write_begin,
  34         .write_end              = simple_write_end,
  35         .set_page_dirty         = __set_page_dirty_no_writeback,
  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                  = noop_fsync,
  46         .splice_read            = generic_file_splice_read,
  47         .splice_write           = generic_file_splice_write,
  48         .llseek                 = generic_file_llseek,
  49 };
  50
  51 const struct inode_operations ramfs_file_inode_operations = {
  52         .setattr                = ramfs_nommu_setattr,
  53         .getattr                = simple_getattr,
  54 };
  55
  56 /*****************************************************************************/
  57 /*
  58  * add a contiguous set of pages into a ramfs inode when it's truncated from
  59  * size 0 on the assumption that it's going to be used for an mmap of shared
  60  * memory
  61  */
  62 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
  63 {
  64         unsigned long npages, xpages, loop;
  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                 return -EFBIG;
  74
  75         ret = inode_newsize_ok(inode, newsize);
  76         if (ret)
  77                 return ret;
  78
  79         i_size_write(inode, newsize);
  80
  81         /* allocate enough contiguous pages to be able to satisfy the
  82          * request */
  83         pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
  84         if (!pages)
  85                 return -ENOMEM;
  86
  87         /* split the high-order page into an array of single pages */
  88         xpages = 1UL << order;
  89         npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  90
  91         split_page(pages, order);
  92
  93         /* trim off any pages we don't actually require */
  94         for (loop = npages; loop < xpages; loop++)
  95                 __free_page(pages + loop);
  96
  97         /* clear the memory we allocated */
  98         newsize = PAGE_SIZE * npages;
  99         data = page_address(pages);
 100         memset(data, 0, newsize);
 101
 102         /* attach all the pages to the inode's address space */
 103         for (loop = 0; loop < npages; loop++) {
 104                 struct page *page = pages + loop;
 105
 106                 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
 107                                         GFP_KERNEL);
 108                 if (ret < 0)
 109                         goto add_error;
 110
 111                 /* prevent the page from being discarded on memory pressure */
 112                 SetPageDirty(page);
 113
 114                 unlock_page(page);
 115                 put_page(page);
 116         }
 117
 118         return 0;
 119
 120 add_error:
 121         while (loop < npages)
 122                 __free_page(pages + loop++);
 123         return ret;
 124 }
 125
 126 /*****************************************************************************/
 127 /*
 128  *
 129  */
 130 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 131 {
 132         int ret;
 133
 134         /* assume a truncate from zero size is going to be for the purposes of
 135          * shared mmap */
 136         if (size == 0) {
 137                 if (unlikely(newsize >> 32))
 138                         return -EFBIG;
 139
 140                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 141         }
 142
 143         /* check that a decrease in size doesn't cut off any shared mappings */
 144         if (newsize < size) {
 145                 ret = nommu_shrink_inode_mappings(inode, size, newsize);
 146                 if (ret < 0)
 147                         return ret;
 148         }
 149
 150         truncate_setsize(inode, newsize);
 151         return 0;
 152 }
 153
 154 /*****************************************************************************/
 155 /*
 156  * handle a change of attributes
 157  * - we're specifically interested in a change of size
 158  */
 159 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 160 {
 161         struct inode *inode = dentry->d_inode;
 162         unsigned int old_ia_valid = ia->ia_valid;
 163         int ret = 0;
 164
 165         /* POSIX UID/GID verification for setting inode attributes */
 166         ret = inode_change_ok(inode, ia);
 167         if (ret)
 168                 return ret;
 169
 170         /* pick out size-changing events */
 171         if (ia->ia_valid & ATTR_SIZE) {
 172                 loff_t size = inode->i_size;
 173
 174                 if (ia->ia_size != size) {
 175                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 176                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 177                                 goto out;
 178                 } else {
 179                         /* we skipped the truncate but must still update
 180                          * timestamps
 181                          */
 182                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 183                 }
 184         }
 185
 186         setattr_copy(inode, ia);
 187  out:
 188         ia->ia_valid = old_ia_valid;
 189         return ret;
 190 }
 191
 192 /*****************************************************************************/
 193 /*
 194  * try to determine where a shared mapping can be made
 195  * - we require that:
 196  *   - the pages to be mapped must exist
 197  *   - the pages be physically contiguous in sequence
 198  */
 199 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 200                                             unsigned long addr, unsigned long len,
 201                                             unsigned long pgoff, unsigned long flags)
 202 {
 203         unsigned long maxpages, lpages, nr, loop, ret;
 204         struct inode *inode = file->f_path.dentry->d_inode;
 205         struct page **pages = NULL, **ptr, *page;
 206         loff_t isize;
 207
 208         if (!(flags & MAP_SHARED))
 209                 return addr;
 210
 211         /* the mapping mustn't extend beyond the EOF */
 212         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 213         isize = i_size_read(inode);
 214
 215         ret = -EINVAL;
 216         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 217         if (pgoff >= maxpages)
 218                 goto out;
 219
 220         if (maxpages - pgoff < lpages)
 221                 goto out;
 222
 223         /* gang-find the pages */
 224         ret = -ENOMEM;
 225         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 226         if (!pages)
 227                 goto out_free;
 228
 229         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 230         if (nr != lpages)
 231                 goto out_free_pages; /* leave if some pages were missing */
 232
 233         /* check the pages for physical adjacency */
 234         ptr = pages;
 235         page = *ptr++;
 236         page++;
 237         for (loop = lpages; loop > 1; loop--)
 238                 if (*ptr++ != page++)
 239                         goto out_free_pages;
 240
 241         /* okay - all conditions fulfilled */
 242         ret = (unsigned long) page_address(pages[0]);
 243
 244 out_free_pages:
 245         ptr = pages;
 246         for (loop = nr; loop > 0; loop--)
 247                 put_page(*ptr++);
 248 out_free:
 249         kfree(pages);
 250 out:
 251         return ret;
 252 }
 253
 254 /*****************************************************************************/
 255 /*
 256  * set up a mapping for shared memory segments
 257  */
 258 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 259 {
 260         if (!(vma->vm_flags & VM_SHARED))
 261                 return -ENOSYS;
 262
 263         file_accessed(file);
 264         vma->vm_ops = &generic_file_vm_ops;
 265         return 0;
 266 }