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Linux/fs/ramfs/file-nommu.c

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  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 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 31                                                    unsigned long addr,
 32                                                    unsigned long len,
 33                                                    unsigned long pgoff,
 34                                                    unsigned long flags);
 35 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma);
 36 
 37 static unsigned ramfs_mmap_capabilities(struct file *file)
 38 {
 39         return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ |
 40                 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
 41 }
 42 
 43 const struct file_operations ramfs_file_operations = {
 44         .mmap_capabilities      = ramfs_mmap_capabilities,
 45         .mmap                   = ramfs_nommu_mmap,
 46         .get_unmapped_area      = ramfs_nommu_get_unmapped_area,
 47         .read_iter              = generic_file_read_iter,
 48         .write_iter             = generic_file_write_iter,
 49         .fsync                  = noop_fsync,
 50         .splice_read            = generic_file_splice_read,
 51         .splice_write           = iter_file_splice_write,
 52         .llseek                 = generic_file_llseek,
 53 };
 54 
 55 const struct inode_operations ramfs_file_inode_operations = {
 56         .setattr                = ramfs_nommu_setattr,
 57         .getattr                = simple_getattr,
 58 };
 59 
 60 /*****************************************************************************/
 61 /*
 62  * add a contiguous set of pages into a ramfs inode when it's truncated from
 63  * size 0 on the assumption that it's going to be used for an mmap of shared
 64  * memory
 65  */
 66 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
 67 {
 68         unsigned long npages, xpages, loop;
 69         struct page *pages;
 70         unsigned order;
 71         void *data;
 72         int ret;
 73         gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
 74 
 75         /* make various checks */
 76         order = get_order(newsize);
 77         if (unlikely(order >= MAX_ORDER))
 78                 return -EFBIG;
 79 
 80         ret = inode_newsize_ok(inode, newsize);
 81         if (ret)
 82                 return ret;
 83 
 84         i_size_write(inode, newsize);
 85 
 86         /* allocate enough contiguous pages to be able to satisfy the
 87          * request */
 88         pages = alloc_pages(gfp, order);
 89         if (!pages)
 90                 return -ENOMEM;
 91 
 92         /* split the high-order page into an array of single pages */
 93         xpages = 1UL << order;
 94         npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
 95 
 96         split_page(pages, order);
 97 
 98         /* trim off any pages we don't actually require */
 99         for (loop = npages; loop < xpages; loop++)
100                 __free_page(pages + loop);
101 
102         /* clear the memory we allocated */
103         newsize = PAGE_SIZE * npages;
104         data = page_address(pages);
105         memset(data, 0, newsize);
106 
107         /* attach all the pages to the inode's address space */
108         for (loop = 0; loop < npages; loop++) {
109                 struct page *page = pages + loop;
110 
111                 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
112                                         gfp);
113                 if (ret < 0)
114                         goto add_error;
115 
116                 /* prevent the page from being discarded on memory pressure */
117                 SetPageDirty(page);
118                 SetPageUptodate(page);
119 
120                 unlock_page(page);
121                 put_page(page);
122         }
123 
124         return 0;
125 
126 add_error:
127         while (loop < npages)
128                 __free_page(pages + loop++);
129         return ret;
130 }
131 
132 /*****************************************************************************/
133 /*
134  *
135  */
136 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
137 {
138         int ret;
139 
140         /* assume a truncate from zero size is going to be for the purposes of
141          * shared mmap */
142         if (size == 0) {
143                 if (unlikely(newsize >> 32))
144                         return -EFBIG;
145 
146                 return ramfs_nommu_expand_for_mapping(inode, newsize);
147         }
148 
149         /* check that a decrease in size doesn't cut off any shared mappings */
150         if (newsize < size) {
151                 ret = nommu_shrink_inode_mappings(inode, size, newsize);
152                 if (ret < 0)
153                         return ret;
154         }
155 
156         truncate_setsize(inode, newsize);
157         return 0;
158 }
159 
160 /*****************************************************************************/
161 /*
162  * handle a change of attributes
163  * - we're specifically interested in a change of size
164  */
165 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
166 {
167         struct inode *inode = d_inode(dentry);
168         unsigned int old_ia_valid = ia->ia_valid;
169         int ret = 0;
170 
171         /* POSIX UID/GID verification for setting inode attributes */
172         ret = inode_change_ok(inode, ia);
173         if (ret)
174                 return ret;
175 
176         /* pick out size-changing events */
177         if (ia->ia_valid & ATTR_SIZE) {
178                 loff_t size = inode->i_size;
179 
180                 if (ia->ia_size != size) {
181                         ret = ramfs_nommu_resize(inode, ia->ia_size, size);
182                         if (ret < 0 || ia->ia_valid == ATTR_SIZE)
183                                 goto out;
184                 } else {
185                         /* we skipped the truncate but must still update
186                          * timestamps
187                          */
188                         ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
189                 }
190         }
191 
192         setattr_copy(inode, ia);
193  out:
194         ia->ia_valid = old_ia_valid;
195         return ret;
196 }
197 
198 /*****************************************************************************/
199 /*
200  * try to determine where a shared mapping can be made
201  * - we require that:
202  *   - the pages to be mapped must exist
203  *   - the pages be physically contiguous in sequence
204  */
205 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
206                                             unsigned long addr, unsigned long len,
207                                             unsigned long pgoff, unsigned long flags)
208 {
209         unsigned long maxpages, lpages, nr, loop, ret;
210         struct inode *inode = file_inode(file);
211         struct page **pages = NULL, **ptr, *page;
212         loff_t isize;
213 
214         if (!(flags & MAP_SHARED))
215                 return addr;
216 
217         /* the mapping mustn't extend beyond the EOF */
218         lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
219         isize = i_size_read(inode);
220 
221         ret = -EINVAL;
222         maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
223         if (pgoff >= maxpages)
224                 goto out;
225 
226         if (maxpages - pgoff < lpages)
227                 goto out;
228 
229         /* gang-find the pages */
230         ret = -ENOMEM;
231         pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL);
232         if (!pages)
233                 goto out_free;
234 
235         nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
236         if (nr != lpages)
237                 goto out_free_pages; /* leave if some pages were missing */
238 
239         /* check the pages for physical adjacency */
240         ptr = pages;
241         page = *ptr++;
242         page++;
243         for (loop = lpages; loop > 1; loop--)
244                 if (*ptr++ != page++)
245                         goto out_free_pages;
246 
247         /* okay - all conditions fulfilled */
248         ret = (unsigned long) page_address(pages[0]);
249 
250 out_free_pages:
251         ptr = pages;
252         for (loop = nr; loop > 0; loop--)
253                 put_page(*ptr++);
254 out_free:
255         kfree(pages);
256 out:
257         return ret;
258 }
259 
260 /*****************************************************************************/
261 /*
262  * set up a mapping for shared memory segments
263  */
264 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
265 {
266         if (!(vma->vm_flags & VM_SHARED))
267                 return -ENOSYS;
268 
269         file_accessed(file);
270         vma->vm_ops = &generic_file_vm_ops;
271         return 0;
272 }
273 

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