udf: Fix races with i_size changes during readpage
[sfrench/cifs-2.6.git] / fs / udf / file.c
1 /*
2  * file.c
3  *
4  * PURPOSE
5  *  File handling routines for the OSTA-UDF(tm) filesystem.
6  *
7  * COPYRIGHT
8  *  This file is distributed under the terms of the GNU General Public
9  *  License (GPL). Copies of the GPL can be obtained from:
10  *    ftp://prep.ai.mit.edu/pub/gnu/GPL
11  *  Each contributing author retains all rights to their own work.
12  *
13  *  (C) 1998-1999 Dave Boynton
14  *  (C) 1998-2004 Ben Fennema
15  *  (C) 1999-2000 Stelias Computing Inc
16  *
17  * HISTORY
18  *
19  *  10/02/98 dgb  Attempt to integrate into udf.o
20  *  10/07/98      Switched to using generic_readpage, etc., like isofs
21  *                And it works!
22  *  12/06/98 blf  Added udf_file_read. uses generic_file_read for all cases but
23  *                ICBTAG_FLAG_AD_IN_ICB.
24  *  04/06/99      64 bit file handling on 32 bit systems taken from ext2 file.c
25  *  05/12/99      Preliminary file write support
26  */
27
28 #include "udfdecl.h"
29 #include <linux/fs.h>
30 #include <linux/uaccess.h>
31 #include <linux/kernel.h>
32 #include <linux/string.h> /* memset */
33 #include <linux/capability.h>
34 #include <linux/errno.h>
35 #include <linux/pagemap.h>
36 #include <linux/uio.h>
37
38 #include "udf_i.h"
39 #include "udf_sb.h"
40
41 static void __udf_adinicb_readpage(struct page *page)
42 {
43         struct inode *inode = page->mapping->host;
44         char *kaddr;
45         struct udf_inode_info *iinfo = UDF_I(inode);
46         loff_t isize = i_size_read(inode);
47
48         /*
49          * We have to be careful here as truncate can change i_size under us.
50          * So just sample it once and use the same value everywhere.
51          */
52         kaddr = kmap_atomic(page);
53         memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, isize);
54         memset(kaddr + isize, 0, PAGE_SIZE - isize);
55         flush_dcache_page(page);
56         SetPageUptodate(page);
57         kunmap_atomic(kaddr);
58 }
59
60 static int udf_adinicb_readpage(struct file *file, struct page *page)
61 {
62         BUG_ON(!PageLocked(page));
63         __udf_adinicb_readpage(page);
64         unlock_page(page);
65
66         return 0;
67 }
68
69 static int udf_adinicb_writepage(struct page *page,
70                                  struct writeback_control *wbc)
71 {
72         struct inode *inode = page->mapping->host;
73         char *kaddr;
74         struct udf_inode_info *iinfo = UDF_I(inode);
75
76         BUG_ON(!PageLocked(page));
77
78         kaddr = kmap_atomic(page);
79         memcpy(iinfo->i_ext.i_data + iinfo->i_lenEAttr, kaddr, inode->i_size);
80         SetPageUptodate(page);
81         kunmap_atomic(kaddr);
82         mark_inode_dirty(inode);
83         unlock_page(page);
84
85         return 0;
86 }
87
88 static int udf_adinicb_write_begin(struct file *file,
89                         struct address_space *mapping, loff_t pos,
90                         unsigned len, unsigned flags, struct page **pagep,
91                         void **fsdata)
92 {
93         struct page *page;
94
95         if (WARN_ON_ONCE(pos >= PAGE_SIZE))
96                 return -EIO;
97         page = grab_cache_page_write_begin(mapping, 0, flags);
98         if (!page)
99                 return -ENOMEM;
100         *pagep = page;
101
102         if (!PageUptodate(page))
103                 __udf_adinicb_readpage(page);
104         return 0;
105 }
106
107 static ssize_t udf_adinicb_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
108 {
109         /* Fallback to buffered I/O. */
110         return 0;
111 }
112
113 static int udf_adinicb_write_end(struct file *file, struct address_space *mapping,
114                                  loff_t pos, unsigned len, unsigned copied,
115                                  struct page *page, void *fsdata)
116 {
117         struct inode *inode = page->mapping->host;
118         loff_t last_pos = pos + copied;
119         if (last_pos > inode->i_size)
120                 i_size_write(inode, last_pos);
121         set_page_dirty(page);
122         unlock_page(page);
123         put_page(page);
124         return copied;
125 }
126
127 const struct address_space_operations udf_adinicb_aops = {
128         .readpage       = udf_adinicb_readpage,
129         .writepage      = udf_adinicb_writepage,
130         .write_begin    = udf_adinicb_write_begin,
131         .write_end      = udf_adinicb_write_end,
132         .direct_IO      = udf_adinicb_direct_IO,
133 };
134
135 static ssize_t udf_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
136 {
137         ssize_t retval;
138         struct file *file = iocb->ki_filp;
139         struct inode *inode = file_inode(file);
140         struct udf_inode_info *iinfo = UDF_I(inode);
141         int err;
142
143         inode_lock(inode);
144
145         retval = generic_write_checks(iocb, from);
146         if (retval <= 0)
147                 goto out;
148
149         down_write(&iinfo->i_data_sem);
150         if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
151                 loff_t end = iocb->ki_pos + iov_iter_count(from);
152
153                 if (inode->i_sb->s_blocksize <
154                                 (udf_file_entry_alloc_offset(inode) + end)) {
155                         err = udf_expand_file_adinicb(inode);
156                         if (err) {
157                                 inode_unlock(inode);
158                                 udf_debug("udf_expand_adinicb: err=%d\n", err);
159                                 return err;
160                         }
161                 } else {
162                         iinfo->i_lenAlloc = max(end, inode->i_size);
163                         up_write(&iinfo->i_data_sem);
164                 }
165         } else
166                 up_write(&iinfo->i_data_sem);
167
168         retval = __generic_file_write_iter(iocb, from);
169 out:
170         inode_unlock(inode);
171
172         if (retval > 0) {
173                 mark_inode_dirty(inode);
174                 retval = generic_write_sync(iocb, retval);
175         }
176
177         return retval;
178 }
179
180 long udf_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
181 {
182         struct inode *inode = file_inode(filp);
183         long old_block, new_block;
184         int result;
185
186         if (inode_permission(inode, MAY_READ) != 0) {
187                 udf_debug("no permission to access inode %lu\n", inode->i_ino);
188                 return -EPERM;
189         }
190
191         if (!arg && ((cmd == UDF_GETVOLIDENT) || (cmd == UDF_GETEASIZE) ||
192                      (cmd == UDF_RELOCATE_BLOCKS) || (cmd == UDF_GETEABLOCK))) {
193                 udf_debug("invalid argument to udf_ioctl\n");
194                 return -EINVAL;
195         }
196
197         switch (cmd) {
198         case UDF_GETVOLIDENT:
199                 if (copy_to_user((char __user *)arg,
200                                  UDF_SB(inode->i_sb)->s_volume_ident, 32))
201                         return -EFAULT;
202                 return 0;
203         case UDF_RELOCATE_BLOCKS:
204                 if (!capable(CAP_SYS_ADMIN))
205                         return -EPERM;
206                 if (get_user(old_block, (long __user *)arg))
207                         return -EFAULT;
208                 result = udf_relocate_blocks(inode->i_sb,
209                                                 old_block, &new_block);
210                 if (result == 0)
211                         result = put_user(new_block, (long __user *)arg);
212                 return result;
213         case UDF_GETEASIZE:
214                 return put_user(UDF_I(inode)->i_lenEAttr, (int __user *)arg);
215         case UDF_GETEABLOCK:
216                 return copy_to_user((char __user *)arg,
217                                     UDF_I(inode)->i_ext.i_data,
218                                     UDF_I(inode)->i_lenEAttr) ? -EFAULT : 0;
219         default:
220                 return -ENOIOCTLCMD;
221         }
222
223         return 0;
224 }
225
226 static int udf_release_file(struct inode *inode, struct file *filp)
227 {
228         if (filp->f_mode & FMODE_WRITE &&
229             atomic_read(&inode->i_writecount) == 1) {
230                 /*
231                  * Grab i_mutex to avoid races with writes changing i_size
232                  * while we are running.
233                  */
234                 inode_lock(inode);
235                 down_write(&UDF_I(inode)->i_data_sem);
236                 udf_discard_prealloc(inode);
237                 udf_truncate_tail_extent(inode);
238                 up_write(&UDF_I(inode)->i_data_sem);
239                 inode_unlock(inode);
240         }
241         return 0;
242 }
243
244 const struct file_operations udf_file_operations = {
245         .read_iter              = generic_file_read_iter,
246         .unlocked_ioctl         = udf_ioctl,
247         .open                   = generic_file_open,
248         .mmap                   = generic_file_mmap,
249         .write_iter             = udf_file_write_iter,
250         .release                = udf_release_file,
251         .fsync                  = generic_file_fsync,
252         .splice_read            = generic_file_splice_read,
253         .llseek                 = generic_file_llseek,
254 };
255
256 static int udf_setattr(struct dentry *dentry, struct iattr *attr)
257 {
258         struct inode *inode = d_inode(dentry);
259         int error;
260
261         error = setattr_prepare(dentry, attr);
262         if (error)
263                 return error;
264
265         if ((attr->ia_valid & ATTR_SIZE) &&
266             attr->ia_size != i_size_read(inode)) {
267                 error = udf_setsize(inode, attr->ia_size);
268                 if (error)
269                         return error;
270         }
271
272         setattr_copy(inode, attr);
273         mark_inode_dirty(inode);
274         return 0;
275 }
276
277 const struct inode_operations udf_file_inode_operations = {
278         .setattr                = udf_setattr,
279 };