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         .splice_write           = generic_file_splice_write,
  47         .llseek                 = generic_file_llseek,
  48 };
  49
  50 const 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 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_file(&lru_pvec);
 116
 117                 /* prevent the page from being discarded on memory pressure */
 118                 SetPageDirty(page);
 119
 120                 unlock_page(page);
 121         }
 122
 123         pagevec_lru_add_file(&lru_pvec);
 124         return 0;
 125
 126  fsize_exceeded:
 127         send_sig(SIGXFSZ, current, 0);
 128  too_big:
 129         return -EFBIG;
 130
 131  add_error:
 132         pagevec_lru_add_file(&lru_pvec);
 133         page_cache_release(pages + loop);
 134         for (loop++; loop < npages; loop++)
 135                 __free_page(pages + loop);
 136         return ret;
 137 }
 138
 139 /*****************************************************************************/
 140 /*
 141  * check that file shrinkage doesn't leave any VMAs dangling in midair
 142  */
 143 static int ramfs_nommu_check_mappings(struct inode *inode,
 144                                       size_t newsize, size_t size)
 145 {
 146         struct vm_area_struct *vma;
 147         struct prio_tree_iter iter;
 148
 149         /* search for VMAs that fall within the dead zone */
 150         vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
 151                               newsize >> PAGE_SHIFT,
 152                               (size + PAGE_SIZE - 1) >> PAGE_SHIFT
 153                               ) {
 154                 /* found one - only interested if it's shared out of the page
 155                  * cache */
 156                 if (vma->vm_flags & VM_SHARED)
 157                         return -ETXTBSY; /* not quite true, but near enough */
 158         }
 159
 160         return 0;
 161 }
 162
 163 /*****************************************************************************/
 164 /*
 165  *
 166  */
 167 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
 168 {
 169         int ret;
 170
 171         /* assume a truncate from zero size is going to be for the purposes of
 172          * shared mmap */
 173         if (size == 0) {
 174                 if (unlikely(newsize >> 32))
 175                         return -EFBIG;
 176
 177                 return ramfs_nommu_expand_for_mapping(inode, newsize);
 178         }
 179
 180         /* check that a decrease in size doesn't cut off any shared mappings */
 181         if (newsize < size) {
 182                 ret = ramfs_nommu_check_mappings(inode, newsize, size);
 183                 if (ret < 0)
 184                         return ret;
 185         }
 186
 187         ret = vmtruncate(inode, newsize);
 188
 189         return ret;
 190 }
 191
 192 /*****************************************************************************/
 193 /*
 194  * handle a change of attributes
 195  * - we're specifically interested in a change of size
 196  */
 197 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
 198 {
 199         struct inode *inode = dentry->d_inode;
 200         unsigned int old_ia_valid = ia->ia_valid;
 201         int ret = 0;
 202
 203         /* POSIX UID/GID verification for setting inode attributes */
 204         ret = inode_change_ok(inode, ia);
 205         if (ret)
 206                 return ret;
 207
 208         /* by providing our own setattr() method, we skip this quotaism */
 209         if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
 210             (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
 211                 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
 212
 213         /* pick out size-changing events */
 214         if (ia->ia_valid & ATTR_SIZE) {
 215                 loff_t size = i_size_read(inode);
 216                 if (ia->ia_size != size) {
 217                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
 218                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
 219                                 goto out;
 220                 } else {
 221                         /* we skipped the truncate but must still update
 222                          * timestamps
 223                          */
 224                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
 225                 }
 226         }
 227
 228         ret = inode_setattr(inode, ia);
 229  out:
 230         ia->ia_valid = old_ia_valid;
 231         return ret;
 232 }
 233
 234 /*****************************************************************************/
 235 /*
 236  * try to determine where a shared mapping can be made
 237  * - we require that:
 238  *   - the pages to be mapped must exist
 239  *   - the pages be physically contiguous in sequence
 240  */
 241 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 242                                             unsigned long addr, unsigned long len,
 243                                             unsigned long pgoff, unsigned long flags)
 244 {
 245         unsigned long maxpages, lpages, nr, loop, ret;
 246         struct inode *inode = file->f_path.dentry->d_inode;
 247         struct page **pages = NULL, **ptr, *page;
 248         loff_t isize;
 249
 250         if (!(flags & MAP_SHARED))
 251                 return addr;
 252
 253         /* the mapping mustn't extend beyond the EOF */
 254         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 255         isize = i_size_read(inode);
 256
 257         ret = -EINVAL;
 258         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 259         if (pgoff >= maxpages)
 260                 goto out;
 261
 262         if (maxpages - pgoff < lpages)
 263                 goto out;
 264
 265         /* gang-find the pages */
 266         ret = -ENOMEM;
 267         pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
 268         if (!pages)
 269                 goto out_free;
 270
 271         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
 272         if (nr != lpages)
 273                 goto out_free_pages; /* leave if some pages were missing */
 274
 275         /* check the pages for physical adjacency */
 276         ptr = pages;
 277         page = *ptr++;
 278         page++;
 279         for (loop = lpages; loop > 1; loop--)
 280                 if (*ptr++ != page++)
 281                         goto out_free_pages;
 282
 283         /* okay - all conditions fulfilled */
 284         ret = (unsigned long) page_address(pages[0]);
 285
 286 out_free_pages:
 287         ptr = pages;
 288         for (loop = nr; loop > 0; loop--)
 289                 put_page(*ptr++);
 290 out_free:
 291         kfree(pages);
 292 out:
 293         return ret;
 294 }
 295
 296 /*****************************************************************************/
 297 /*
 298  * set up a mapping for shared memory segments
 299  */
 300 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
 301 {
 302         if (!(vma->vm_flags & VM_SHARED))
 303                 return -ENOSYS;
 304
 305         file_accessed(file);
 306         vma->vm_ops = &generic_file_vm_ops;
 307         return 0;
 308 }