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TOMOYO Linux Cross Reference
Linux/fs/ext4/mmp.c

Version: ~ [ linux-5.5-rc1 ] ~ [ linux-5.4.2 ] ~ [ linux-5.3.15 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.88 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.158 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.206 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.206 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.78 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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  1 #include <linux/fs.h>
  2 #include <linux/random.h>
  3 #include <linux/buffer_head.h>
  4 #include <linux/utsname.h>
  5 #include <linux/kthread.h>
  6 
  7 #include "ext4.h"
  8 
  9 /* Checksumming functions */
 10 static __u32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
 11 {
 12         struct ext4_sb_info *sbi = EXT4_SB(sb);
 13         int offset = offsetof(struct mmp_struct, mmp_checksum);
 14         __u32 csum;
 15 
 16         csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
 17 
 18         return cpu_to_le32(csum);
 19 }
 20 
 21 int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
 22 {
 23         if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
 24                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
 25                 return 1;
 26 
 27         return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
 28 }
 29 
 30 void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
 31 {
 32         if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
 33                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
 34                 return;
 35 
 36         mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
 37 }
 38 
 39 /*
 40  * Write the MMP block using WRITE_SYNC to try to get the block on-disk
 41  * faster.
 42  */
 43 static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
 44 {
 45         struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
 46 
 47         /*
 48          * We protect against freezing so that we don't create dirty buffers
 49          * on frozen filesystem.
 50          */
 51         sb_start_write(sb);
 52         ext4_mmp_csum_set(sb, mmp);
 53         mark_buffer_dirty(bh);
 54         lock_buffer(bh);
 55         bh->b_end_io = end_buffer_write_sync;
 56         get_bh(bh);
 57         submit_bh(WRITE_SYNC, bh);
 58         wait_on_buffer(bh);
 59         sb_end_write(sb);
 60         if (unlikely(!buffer_uptodate(bh)))
 61                 return 1;
 62 
 63         return 0;
 64 }
 65 
 66 /*
 67  * Read the MMP block. It _must_ be read from disk and hence we clear the
 68  * uptodate flag on the buffer.
 69  */
 70 static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
 71                           ext4_fsblk_t mmp_block)
 72 {
 73         struct mmp_struct *mmp;
 74 
 75         if (*bh)
 76                 clear_buffer_uptodate(*bh);
 77 
 78         /* This would be sb_bread(sb, mmp_block), except we need to be sure
 79          * that the MD RAID device cache has been bypassed, and that the read
 80          * is not blocked in the elevator. */
 81         if (!*bh)
 82                 *bh = sb_getblk(sb, mmp_block);
 83         if (*bh) {
 84                 get_bh(*bh);
 85                 lock_buffer(*bh);
 86                 (*bh)->b_end_io = end_buffer_read_sync;
 87                 submit_bh(READ_SYNC, *bh);
 88                 wait_on_buffer(*bh);
 89                 if (!buffer_uptodate(*bh)) {
 90                         brelse(*bh);
 91                         *bh = NULL;
 92                 }
 93         }
 94         if (!*bh) {
 95                 ext4_warning(sb, "Error while reading MMP block %llu",
 96                              mmp_block);
 97                 return -EIO;
 98         }
 99 
100         mmp = (struct mmp_struct *)((*bh)->b_data);
101         if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC ||
102             !ext4_mmp_csum_verify(sb, mmp))
103                 return -EINVAL;
104 
105         return 0;
106 }
107 
108 /*
109  * Dump as much information as possible to help the admin.
110  */
111 void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
112                     const char *function, unsigned int line, const char *msg)
113 {
114         __ext4_warning(sb, function, line, msg);
115         __ext4_warning(sb, function, line,
116                        "MMP failure info: last update time: %llu, last update "
117                        "node: %s, last update device: %s\n",
118                        (long long unsigned int) le64_to_cpu(mmp->mmp_time),
119                        mmp->mmp_nodename, mmp->mmp_bdevname);
120 }
121 
122 /*
123  * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
124  */
125 static int kmmpd(void *data)
126 {
127         struct super_block *sb = ((struct mmpd_data *) data)->sb;
128         struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
129         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
130         struct mmp_struct *mmp;
131         ext4_fsblk_t mmp_block;
132         u32 seq = 0;
133         unsigned long failed_writes = 0;
134         int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
135         unsigned mmp_check_interval;
136         unsigned long last_update_time;
137         unsigned long diff;
138         int retval;
139 
140         mmp_block = le64_to_cpu(es->s_mmp_block);
141         mmp = (struct mmp_struct *)(bh->b_data);
142         mmp->mmp_time = cpu_to_le64(get_seconds());
143         /*
144          * Start with the higher mmp_check_interval and reduce it if
145          * the MMP block is being updated on time.
146          */
147         mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
148                                  EXT4_MMP_MIN_CHECK_INTERVAL);
149         mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
150         bdevname(bh->b_bdev, mmp->mmp_bdevname);
151 
152         memcpy(mmp->mmp_nodename, init_utsname()->nodename,
153                sizeof(mmp->mmp_nodename));
154 
155         while (!kthread_should_stop()) {
156                 if (++seq > EXT4_MMP_SEQ_MAX)
157                         seq = 1;
158 
159                 mmp->mmp_seq = cpu_to_le32(seq);
160                 mmp->mmp_time = cpu_to_le64(get_seconds());
161                 last_update_time = jiffies;
162 
163                 retval = write_mmp_block(sb, bh);
164                 /*
165                  * Don't spew too many error messages. Print one every
166                  * (s_mmp_update_interval * 60) seconds.
167                  */
168                 if (retval) {
169                         if ((failed_writes % 60) == 0)
170                                 ext4_error(sb, "Error writing to MMP block");
171                         failed_writes++;
172                 }
173 
174                 if (!(le32_to_cpu(es->s_feature_incompat) &
175                     EXT4_FEATURE_INCOMPAT_MMP)) {
176                         ext4_warning(sb, "kmmpd being stopped since MMP feature"
177                                      " has been disabled.");
178                         EXT4_SB(sb)->s_mmp_tsk = NULL;
179                         goto failed;
180                 }
181 
182                 if (sb->s_flags & MS_RDONLY) {
183                         ext4_warning(sb, "kmmpd being stopped since filesystem "
184                                      "has been remounted as readonly.");
185                         EXT4_SB(sb)->s_mmp_tsk = NULL;
186                         goto failed;
187                 }
188 
189                 diff = jiffies - last_update_time;
190                 if (diff < mmp_update_interval * HZ)
191                         schedule_timeout_interruptible(mmp_update_interval *
192                                                        HZ - diff);
193 
194                 /*
195                  * We need to make sure that more than mmp_check_interval
196                  * seconds have not passed since writing. If that has happened
197                  * we need to check if the MMP block is as we left it.
198                  */
199                 diff = jiffies - last_update_time;
200                 if (diff > mmp_check_interval * HZ) {
201                         struct buffer_head *bh_check = NULL;
202                         struct mmp_struct *mmp_check;
203 
204                         retval = read_mmp_block(sb, &bh_check, mmp_block);
205                         if (retval) {
206                                 ext4_error(sb, "error reading MMP data: %d",
207                                            retval);
208 
209                                 EXT4_SB(sb)->s_mmp_tsk = NULL;
210                                 goto failed;
211                         }
212 
213                         mmp_check = (struct mmp_struct *)(bh_check->b_data);
214                         if (mmp->mmp_seq != mmp_check->mmp_seq ||
215                             memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
216                                    sizeof(mmp->mmp_nodename))) {
217                                 dump_mmp_msg(sb, mmp_check,
218                                              "Error while updating MMP info. "
219                                              "The filesystem seems to have been"
220                                              " multiply mounted.");
221                                 ext4_error(sb, "abort");
222                                 goto failed;
223                         }
224                         put_bh(bh_check);
225                 }
226 
227                  /*
228                  * Adjust the mmp_check_interval depending on how much time
229                  * it took for the MMP block to be written.
230                  */
231                 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
232                                              EXT4_MMP_MAX_CHECK_INTERVAL),
233                                          EXT4_MMP_MIN_CHECK_INTERVAL);
234                 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
235         }
236 
237         /*
238          * Unmount seems to be clean.
239          */
240         mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
241         mmp->mmp_time = cpu_to_le64(get_seconds());
242 
243         retval = write_mmp_block(sb, bh);
244 
245 failed:
246         kfree(data);
247         brelse(bh);
248         return retval;
249 }
250 
251 /*
252  * Get a random new sequence number but make sure it is not greater than
253  * EXT4_MMP_SEQ_MAX.
254  */
255 static unsigned int mmp_new_seq(void)
256 {
257         u32 new_seq;
258 
259         do {
260                 get_random_bytes(&new_seq, sizeof(u32));
261         } while (new_seq > EXT4_MMP_SEQ_MAX);
262 
263         return new_seq;
264 }
265 
266 /*
267  * Protect the filesystem from being mounted more than once.
268  */
269 int ext4_multi_mount_protect(struct super_block *sb,
270                                     ext4_fsblk_t mmp_block)
271 {
272         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
273         struct buffer_head *bh = NULL;
274         struct mmp_struct *mmp = NULL;
275         struct mmpd_data *mmpd_data;
276         u32 seq;
277         unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
278         unsigned int wait_time = 0;
279         int retval;
280 
281         if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
282             mmp_block >= ext4_blocks_count(es)) {
283                 ext4_warning(sb, "Invalid MMP block in superblock");
284                 goto failed;
285         }
286 
287         retval = read_mmp_block(sb, &bh, mmp_block);
288         if (retval)
289                 goto failed;
290 
291         mmp = (struct mmp_struct *)(bh->b_data);
292 
293         if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
294                 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
295 
296         /*
297          * If check_interval in MMP block is larger, use that instead of
298          * update_interval from the superblock.
299          */
300         if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
301                 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
302 
303         seq = le32_to_cpu(mmp->mmp_seq);
304         if (seq == EXT4_MMP_SEQ_CLEAN)
305                 goto skip;
306 
307         if (seq == EXT4_MMP_SEQ_FSCK) {
308                 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
309                 goto failed;
310         }
311 
312         wait_time = min(mmp_check_interval * 2 + 1,
313                         mmp_check_interval + 60);
314 
315         /* Print MMP interval if more than 20 secs. */
316         if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
317                 ext4_warning(sb, "MMP interval %u higher than expected, please"
318                              " wait.\n", wait_time * 2);
319 
320         if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
321                 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
322                 goto failed;
323         }
324 
325         retval = read_mmp_block(sb, &bh, mmp_block);
326         if (retval)
327                 goto failed;
328         mmp = (struct mmp_struct *)(bh->b_data);
329         if (seq != le32_to_cpu(mmp->mmp_seq)) {
330                 dump_mmp_msg(sb, mmp,
331                              "Device is already active on another node.");
332                 goto failed;
333         }
334 
335 skip:
336         /*
337          * write a new random sequence number.
338          */
339         seq = mmp_new_seq();
340         mmp->mmp_seq = cpu_to_le32(seq);
341 
342         retval = write_mmp_block(sb, bh);
343         if (retval)
344                 goto failed;
345 
346         /*
347          * wait for MMP interval and check mmp_seq.
348          */
349         if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
350                 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
351                 goto failed;
352         }
353 
354         retval = read_mmp_block(sb, &bh, mmp_block);
355         if (retval)
356                 goto failed;
357         mmp = (struct mmp_struct *)(bh->b_data);
358         if (seq != le32_to_cpu(mmp->mmp_seq)) {
359                 dump_mmp_msg(sb, mmp,
360                              "Device is already active on another node.");
361                 goto failed;
362         }
363 
364         mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
365         if (!mmpd_data) {
366                 ext4_warning(sb, "not enough memory for mmpd_data");
367                 goto failed;
368         }
369         mmpd_data->sb = sb;
370         mmpd_data->bh = bh;
371 
372         /*
373          * Start a kernel thread to update the MMP block periodically.
374          */
375         EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
376                                              bdevname(bh->b_bdev,
377                                                       mmp->mmp_bdevname));
378         if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
379                 EXT4_SB(sb)->s_mmp_tsk = NULL;
380                 kfree(mmpd_data);
381                 ext4_warning(sb, "Unable to create kmmpd thread for %s.",
382                              sb->s_id);
383                 goto failed;
384         }
385 
386         return 0;
387 
388 failed:
389         brelse(bh);
390         return 1;
391 }
392 
393 
394 

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