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         }
 116
 117         return 0;
 118
 119 add_error:
 120         while (loop < npages)
 121                 __free_page(pages + loop++);
 122         return ret;
 123 }
 124
 125 /*****************************************************************************/
 126 /*
 127  *
 128  */
 129 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 130 {
 131         int ret;
 132
 133         /* assume a truncate from zero size is going to be for the purposes of
 134          * shared mmap */
 135         if (size == 0) {
 136                 if (unlikely(newsize >> 32))
 137                         return -EFBIG;
 138
 139                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 140         }
 141
 142         /* check that a decrease in size doesn't cut off any shared mappings */
 143         if (newsize < size) {
 144                 ret = nommu_shrink_inode_mappings(inode, size, newsize);
 145                 if (ret < 0)
 146                         return ret;
 147         }
 148
 149         truncate_setsize(inode, newsize);
 150         return 0;
 151 }
 152
 153 /*****************************************************************************/
 154 /*
 155  * handle a change of attributes
 156  * - we're specifically interested in a change of size
 157  */
 158 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 159 {
 160         struct inode *inode = dentry->d_inode;
 161         unsigned int old_ia_valid = ia->ia_valid;
 162         int ret = 0;
 163
 164         /* POSIX UID/GID verification for setting inode attributes */
 165         ret = inode_change_ok(inode, ia);
 166         if (ret)
 167                 return ret;
 168
 169         /* pick out size-changing events */
 170         if (ia->ia_valid & ATTR_SIZE) {
 171                 loff_t size = inode->i_size;
 172
 173                 if (ia->ia_size != size) {
 174                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 175                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 176                                 goto out;
 177                 } else {
 178                         /* we skipped the truncate but must still update
 179                          * timestamps
 180                          */
 181                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 182                 }
 183         }
 184
 185         setattr_copy(inode, ia);
 186  out:
 187         ia->ia_valid = old_ia_valid;
 188         return ret;
 189 }
 190
 191 /*****************************************************************************/
 192 /*
 193  * try to determine where a shared mapping can be made
 194  * - we require that:
 195  *   - the pages to be mapped must exist
 196  *   - the pages be physically contiguous in sequence
 197  */
 198 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 199                                             unsigned long addr, unsigned long len,
 200                                             unsigned long pgoff, unsigned long flags)
 201 {
 202         unsigned long maxpages, lpages, nr, loop, ret;
 203         struct inode *inode = file->f_path.dentry->d_inode;
 204         struct page **pages = NULL, **ptr, *page;
 205         loff_t isize;
 206
 207         if (!(flags & MAP_SHARED))
 208                 return addr;
 209
 210         /* the mapping mustn't extend beyond the EOF */
 211         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 212         isize = i_size_read(inode);
 213
 214         ret = -EINVAL;
 215         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 216         if (pgoff >= maxpages)
 217                 goto out;
 218
 219         if (maxpages - pgoff < lpages)
 220                 goto out;
 221
 222         /* gang-find the pages */
 223         ret = -ENOMEM;
 224         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 225         if (!pages)
 226                 goto out_free;
 227
 228         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 229         if (nr != lpages)
 230                 goto out_free_pages; /* leave if some pages were missing */
 231
 232         /* check the pages for physical adjacency */
 233         ptr = pages;
 234         page = *ptr++;
 235         page++;
 236         for (loop = lpages; loop > 1; loop--)
 237                 if (*ptr++ != page++)
 238                         goto out_free_pages;
 239
 240         /* okay - all conditions fulfilled */
 241         ret = (unsigned long) page_address(pages[0]);
 242
 243 out_free_pages:
 244         ptr = pages;
 245         for (loop = nr; loop > 0; loop--)
 246                 put_page(*ptr++);
 247 out_free:
 248         kfree(pages);
 249 out:
 250         return ret;
 251 }
 252
 253 /*****************************************************************************/
 254 /*
 255  * set up a mapping for shared memory segments
 256  */
 257 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 258 {
 259         if (!(vma->vm_flags & VM_SHARED))
 260                 return -ENOSYS;
 261
 262         file_accessed(file);
 263         vma->vm_ops = &generic_file_vm_ops;
 264         return 0;
 265 }