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 } 267