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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 */
10static __le32 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
21int 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
30void 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 */
43static 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 | REQ_META | REQ_PRIO, 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 */
70static 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 return -ENOMEM;
85 if (*bh) {
86 get_bh(*bh);
87 lock_buffer(*bh);
88 (*bh)->b_end_io = end_buffer_read_sync;
89 submit_bh(READ_SYNC | REQ_META | REQ_PRIO, *bh);
90 wait_on_buffer(*bh);
91 if (!buffer_uptodate(*bh)) {
92 brelse(*bh);
93 *bh = NULL;
94 }
95 }
96 if (unlikely(!*bh)) {
97 ext4_warning(sb, "Error while reading MMP block %llu",
98 mmp_block);
99 return -EIO;
100 }
101
102 mmp = (struct mmp_struct *)((*bh)->b_data);
103 if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC ||
104 !ext4_mmp_csum_verify(sb, mmp))
105 return -EINVAL;
106
107 return 0;
108}
109
110/*
111 * Dump as much information as possible to help the admin.
112 */
113void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
114 const char *function, unsigned int line, const char *msg)
115{
116 __ext4_warning(sb, function, line, msg);
117 __ext4_warning(sb, function, line,
118 "MMP failure info: last update time: %llu, last update "
119 "node: %s, last update device: %s\n",
120 (long long unsigned int) le64_to_cpu(mmp->mmp_time),
121 mmp->mmp_nodename, mmp->mmp_bdevname);
122}
123
124/*
125 * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
126 */
127static int kmmpd(void *data)
128{
129 struct super_block *sb = ((struct mmpd_data *) data)->sb;
130 struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
131 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
132 struct mmp_struct *mmp;
133 ext4_fsblk_t mmp_block;
134 u32 seq = 0;
135 unsigned long failed_writes = 0;
136 int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
137 unsigned mmp_check_interval;
138 unsigned long last_update_time;
139 unsigned long diff;
140 int retval;
141
142 mmp_block = le64_to_cpu(es->s_mmp_block);
143 mmp = (struct mmp_struct *)(bh->b_data);
144 mmp->mmp_time = cpu_to_le64(get_seconds());
145 /*
146 * Start with the higher mmp_check_interval and reduce it if
147 * the MMP block is being updated on time.
148 */
149 mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
150 EXT4_MMP_MIN_CHECK_INTERVAL);
151 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
152 bdevname(bh->b_bdev, mmp->mmp_bdevname);
153
154 memcpy(mmp->mmp_nodename, init_utsname()->nodename,
155 sizeof(mmp->mmp_nodename));
156
157 while (!kthread_should_stop()) {
158 if (++seq > EXT4_MMP_SEQ_MAX)
159 seq = 1;
160
161 mmp->mmp_seq = cpu_to_le32(seq);
162 mmp->mmp_time = cpu_to_le64(get_seconds());
163 last_update_time = jiffies;
164
165 retval = write_mmp_block(sb, bh);
166 /*
167 * Don't spew too many error messages. Print one every
168 * (s_mmp_update_interval * 60) seconds.
169 */
170 if (retval) {
171 if ((failed_writes % 60) == 0)
172 ext4_error(sb, "Error writing to MMP block");
173 failed_writes++;
174 }
175
176 if (!(le32_to_cpu(es->s_feature_incompat) &
177 EXT4_FEATURE_INCOMPAT_MMP)) {
178 ext4_warning(sb, "kmmpd being stopped since MMP feature"
179 " has been disabled.");
180 EXT4_SB(sb)->s_mmp_tsk = NULL;
181 goto failed;
182 }
183
184 if (sb->s_flags & MS_RDONLY) {
185 ext4_warning(sb, "kmmpd being stopped since filesystem "
186 "has been remounted as readonly.");
187 EXT4_SB(sb)->s_mmp_tsk = NULL;
188 goto failed;
189 }
190
191 diff = jiffies - last_update_time;
192 if (diff < mmp_update_interval * HZ)
193 schedule_timeout_interruptible(mmp_update_interval *
194 HZ - diff);
195
196 /*
197 * We need to make sure that more than mmp_check_interval
198 * seconds have not passed since writing. If that has happened
199 * we need to check if the MMP block is as we left it.
200 */
201 diff = jiffies - last_update_time;
202 if (diff > mmp_check_interval * HZ) {
203 struct buffer_head *bh_check = NULL;
204 struct mmp_struct *mmp_check;
205
206 retval = read_mmp_block(sb, &bh_check, mmp_block);
207 if (retval) {
208 ext4_error(sb, "error reading MMP data: %d",
209 retval);
210
211 EXT4_SB(sb)->s_mmp_tsk = NULL;
212 goto failed;
213 }
214
215 mmp_check = (struct mmp_struct *)(bh_check->b_data);
216 if (mmp->mmp_seq != mmp_check->mmp_seq ||
217 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
218 sizeof(mmp->mmp_nodename))) {
219 dump_mmp_msg(sb, mmp_check,
220 "Error while updating MMP info. "
221 "The filesystem seems to have been"
222 " multiply mounted.");
223 ext4_error(sb, "abort");
224 goto failed;
225 }
226 put_bh(bh_check);
227 }
228
229 /*
230 * Adjust the mmp_check_interval depending on how much time
231 * it took for the MMP block to be written.
232 */
233 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
234 EXT4_MMP_MAX_CHECK_INTERVAL),
235 EXT4_MMP_MIN_CHECK_INTERVAL);
236 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
237 }
238
239 /*
240 * Unmount seems to be clean.
241 */
242 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
243 mmp->mmp_time = cpu_to_le64(get_seconds());
244
245 retval = write_mmp_block(sb, bh);
246
247failed:
248 kfree(data);
249 brelse(bh);
250 return retval;
251}
252
253/*
254 * Get a random new sequence number but make sure it is not greater than
255 * EXT4_MMP_SEQ_MAX.
256 */
257static unsigned int mmp_new_seq(void)
258{
259 u32 new_seq;
260
261 do {
262 new_seq = prandom_u32();
263 } while (new_seq > EXT4_MMP_SEQ_MAX);
264
265 return new_seq;
266}
267
268/*
269 * Protect the filesystem from being mounted more than once.
270 */
271int ext4_multi_mount_protect(struct super_block *sb,
272 ext4_fsblk_t mmp_block)
273{
274 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
275 struct buffer_head *bh = NULL;
276 struct mmp_struct *mmp = NULL;
277 struct mmpd_data *mmpd_data;
278 u32 seq;
279 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
280 unsigned int wait_time = 0;
281 int retval;
282
283 if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
284 mmp_block >= ext4_blocks_count(es)) {
285 ext4_warning(sb, "Invalid MMP block in superblock");
286 goto failed;
287 }
288
289 retval = read_mmp_block(sb, &bh, mmp_block);
290 if (retval)
291 goto failed;
292
293 mmp = (struct mmp_struct *)(bh->b_data);
294
295 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
296 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
297
298 /*
299 * If check_interval in MMP block is larger, use that instead of
300 * update_interval from the superblock.
301 */
302 if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
303 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
304
305 seq = le32_to_cpu(mmp->mmp_seq);
306 if (seq == EXT4_MMP_SEQ_CLEAN)
307 goto skip;
308
309 if (seq == EXT4_MMP_SEQ_FSCK) {
310 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
311 goto failed;
312 }
313
314 wait_time = min(mmp_check_interval * 2 + 1,
315 mmp_check_interval + 60);
316
317 /* Print MMP interval if more than 20 secs. */
318 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
319 ext4_warning(sb, "MMP interval %u higher than expected, please"
320 " wait.\n", wait_time * 2);
321
322 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
323 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
324 goto failed;
325 }
326
327 retval = read_mmp_block(sb, &bh, mmp_block);
328 if (retval)
329 goto failed;
330 mmp = (struct mmp_struct *)(bh->b_data);
331 if (seq != le32_to_cpu(mmp->mmp_seq)) {
332 dump_mmp_msg(sb, mmp,
333 "Device is already active on another node.");
334 goto failed;
335 }
336
337skip:
338 /*
339 * write a new random sequence number.
340 */
341 seq = mmp_new_seq();
342 mmp->mmp_seq = cpu_to_le32(seq);
343
344 retval = write_mmp_block(sb, bh);
345 if (retval)
346 goto failed;
347
348 /*
349 * wait for MMP interval and check mmp_seq.
350 */
351 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
352 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
353 goto failed;
354 }
355
356 retval = read_mmp_block(sb, &bh, mmp_block);
357 if (retval)
358 goto failed;
359 mmp = (struct mmp_struct *)(bh->b_data);
360 if (seq != le32_to_cpu(mmp->mmp_seq)) {
361 dump_mmp_msg(sb, mmp,
362 "Device is already active on another node.");
363 goto failed;
364 }
365
366 mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
367 if (!mmpd_data) {
368 ext4_warning(sb, "not enough memory for mmpd_data");
369 goto failed;
370 }
371 mmpd_data->sb = sb;
372 mmpd_data->bh = bh;
373
374 /*
375 * Start a kernel thread to update the MMP block periodically.
376 */
377 EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
378 bdevname(bh->b_bdev,
379 mmp->mmp_bdevname));
380 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
381 EXT4_SB(sb)->s_mmp_tsk = NULL;
382 kfree(mmpd_data);
383 ext4_warning(sb, "Unable to create kmmpd thread for %s.",
384 sb->s_id);
385 goto failed;
386 }
387
388 return 0;
389
390failed:
391 brelse(bh);
392 return 1;
393}
394
395
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/fs.h>
3#include <linux/random.h>
4#include <linux/buffer_head.h>
5#include <linux/utsname.h>
6#include <linux/kthread.h>
7
8#include "ext4.h"
9
10/* Checksumming functions */
11static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
12{
13 struct ext4_sb_info *sbi = EXT4_SB(sb);
14 int offset = offsetof(struct mmp_struct, mmp_checksum);
15 __u32 csum;
16
17 csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
18
19 return cpu_to_le32(csum);
20}
21
22static int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
23{
24 if (!ext4_has_metadata_csum(sb))
25 return 1;
26
27 return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
28}
29
30static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
31{
32 if (!ext4_has_metadata_csum(sb))
33 return;
34
35 mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
36}
37
38/*
39 * Write the MMP block using REQ_SYNC to try to get the block on-disk
40 * faster.
41 */
42static int write_mmp_block_thawed(struct super_block *sb,
43 struct buffer_head *bh)
44{
45 struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
46
47 ext4_mmp_csum_set(sb, mmp);
48 lock_buffer(bh);
49 bh->b_end_io = end_buffer_write_sync;
50 get_bh(bh);
51 submit_bh(REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO, bh);
52 wait_on_buffer(bh);
53 if (unlikely(!buffer_uptodate(bh)))
54 return -EIO;
55 return 0;
56}
57
58static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
59{
60 int err;
61
62 /*
63 * We protect against freezing so that we don't create dirty buffers
64 * on frozen filesystem.
65 */
66 sb_start_write(sb);
67 err = write_mmp_block_thawed(sb, bh);
68 sb_end_write(sb);
69 return err;
70}
71
72/*
73 * Read the MMP block. It _must_ be read from disk and hence we clear the
74 * uptodate flag on the buffer.
75 */
76static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
77 ext4_fsblk_t mmp_block)
78{
79 struct mmp_struct *mmp;
80 int ret;
81
82 if (*bh)
83 clear_buffer_uptodate(*bh);
84
85 /* This would be sb_bread(sb, mmp_block), except we need to be sure
86 * that the MD RAID device cache has been bypassed, and that the read
87 * is not blocked in the elevator. */
88 if (!*bh) {
89 *bh = sb_getblk(sb, mmp_block);
90 if (!*bh) {
91 ret = -ENOMEM;
92 goto warn_exit;
93 }
94 }
95
96 lock_buffer(*bh);
97 ret = ext4_read_bh(*bh, REQ_META | REQ_PRIO, NULL);
98 if (ret)
99 goto warn_exit;
100
101 mmp = (struct mmp_struct *)((*bh)->b_data);
102 if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC) {
103 ret = -EFSCORRUPTED;
104 goto warn_exit;
105 }
106 if (!ext4_mmp_csum_verify(sb, mmp)) {
107 ret = -EFSBADCRC;
108 goto warn_exit;
109 }
110 return 0;
111warn_exit:
112 brelse(*bh);
113 *bh = NULL;
114 ext4_warning(sb, "Error %d while reading MMP block %llu",
115 ret, mmp_block);
116 return ret;
117}
118
119/*
120 * Dump as much information as possible to help the admin.
121 */
122void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
123 const char *function, unsigned int line, const char *msg)
124{
125 __ext4_warning(sb, function, line, "%s", msg);
126 __ext4_warning(sb, function, line,
127 "MMP failure info: last update time: %llu, last update node: %.*s, last update device: %.*s",
128 (unsigned long long)le64_to_cpu(mmp->mmp_time),
129 (int)sizeof(mmp->mmp_nodename), mmp->mmp_nodename,
130 (int)sizeof(mmp->mmp_bdevname), mmp->mmp_bdevname);
131}
132
133/*
134 * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
135 */
136static int kmmpd(void *data)
137{
138 struct super_block *sb = data;
139 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
140 struct buffer_head *bh = EXT4_SB(sb)->s_mmp_bh;
141 struct mmp_struct *mmp;
142 ext4_fsblk_t mmp_block;
143 u32 seq = 0;
144 unsigned long failed_writes = 0;
145 int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
146 unsigned mmp_check_interval;
147 unsigned long last_update_time;
148 unsigned long diff;
149 int retval = 0;
150
151 mmp_block = le64_to_cpu(es->s_mmp_block);
152 mmp = (struct mmp_struct *)(bh->b_data);
153 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
154 /*
155 * Start with the higher mmp_check_interval and reduce it if
156 * the MMP block is being updated on time.
157 */
158 mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
159 EXT4_MMP_MIN_CHECK_INTERVAL);
160 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
161
162 memcpy(mmp->mmp_nodename, init_utsname()->nodename,
163 sizeof(mmp->mmp_nodename));
164
165 while (!kthread_should_stop() && !ext4_forced_shutdown(sb)) {
166 if (!ext4_has_feature_mmp(sb)) {
167 ext4_warning(sb, "kmmpd being stopped since MMP feature"
168 " has been disabled.");
169 goto wait_to_exit;
170 }
171 if (++seq > EXT4_MMP_SEQ_MAX)
172 seq = 1;
173
174 mmp->mmp_seq = cpu_to_le32(seq);
175 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
176 last_update_time = jiffies;
177
178 retval = write_mmp_block(sb, bh);
179 /*
180 * Don't spew too many error messages. Print one every
181 * (s_mmp_update_interval * 60) seconds.
182 */
183 if (retval) {
184 if ((failed_writes % 60) == 0) {
185 ext4_error_err(sb, -retval,
186 "Error writing to MMP block");
187 }
188 failed_writes++;
189 }
190
191 diff = jiffies - last_update_time;
192 if (diff < mmp_update_interval * HZ)
193 schedule_timeout_interruptible(mmp_update_interval *
194 HZ - diff);
195
196 /*
197 * We need to make sure that more than mmp_check_interval
198 * seconds have not passed since writing. If that has happened
199 * we need to check if the MMP block is as we left it.
200 */
201 diff = jiffies - last_update_time;
202 if (diff > mmp_check_interval * HZ) {
203 struct buffer_head *bh_check = NULL;
204 struct mmp_struct *mmp_check;
205
206 retval = read_mmp_block(sb, &bh_check, mmp_block);
207 if (retval) {
208 ext4_error_err(sb, -retval,
209 "error reading MMP data: %d",
210 retval);
211 goto wait_to_exit;
212 }
213
214 mmp_check = (struct mmp_struct *)(bh_check->b_data);
215 if (mmp->mmp_seq != mmp_check->mmp_seq ||
216 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
217 sizeof(mmp->mmp_nodename))) {
218 dump_mmp_msg(sb, mmp_check,
219 "Error while updating MMP info. "
220 "The filesystem seems to have been"
221 " multiply mounted.");
222 ext4_error_err(sb, EBUSY, "abort");
223 put_bh(bh_check);
224 retval = -EBUSY;
225 goto wait_to_exit;
226 }
227 put_bh(bh_check);
228 }
229
230 /*
231 * Adjust the mmp_check_interval depending on how much time
232 * it took for the MMP block to be written.
233 */
234 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
235 EXT4_MMP_MAX_CHECK_INTERVAL),
236 EXT4_MMP_MIN_CHECK_INTERVAL);
237 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
238 }
239
240 /*
241 * Unmount seems to be clean.
242 */
243 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
244 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
245
246 retval = write_mmp_block(sb, bh);
247
248wait_to_exit:
249 while (!kthread_should_stop()) {
250 set_current_state(TASK_INTERRUPTIBLE);
251 if (!kthread_should_stop())
252 schedule();
253 }
254 set_current_state(TASK_RUNNING);
255 return retval;
256}
257
258void ext4_stop_mmpd(struct ext4_sb_info *sbi)
259{
260 if (sbi->s_mmp_tsk) {
261 kthread_stop(sbi->s_mmp_tsk);
262 brelse(sbi->s_mmp_bh);
263 sbi->s_mmp_tsk = NULL;
264 }
265}
266
267/*
268 * Get a random new sequence number but make sure it is not greater than
269 * EXT4_MMP_SEQ_MAX.
270 */
271static unsigned int mmp_new_seq(void)
272{
273 return get_random_u32_below(EXT4_MMP_SEQ_MAX + 1);
274}
275
276/*
277 * Protect the filesystem from being mounted more than once.
278 */
279int ext4_multi_mount_protect(struct super_block *sb,
280 ext4_fsblk_t mmp_block)
281{
282 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
283 struct buffer_head *bh = NULL;
284 struct mmp_struct *mmp = NULL;
285 u32 seq;
286 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
287 unsigned int wait_time = 0;
288 int retval;
289
290 if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
291 mmp_block >= ext4_blocks_count(es)) {
292 ext4_warning(sb, "Invalid MMP block in superblock");
293 retval = -EINVAL;
294 goto failed;
295 }
296
297 retval = read_mmp_block(sb, &bh, mmp_block);
298 if (retval)
299 goto failed;
300
301 mmp = (struct mmp_struct *)(bh->b_data);
302
303 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
304 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
305
306 /*
307 * If check_interval in MMP block is larger, use that instead of
308 * update_interval from the superblock.
309 */
310 if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
311 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
312
313 seq = le32_to_cpu(mmp->mmp_seq);
314 if (seq == EXT4_MMP_SEQ_CLEAN)
315 goto skip;
316
317 if (seq == EXT4_MMP_SEQ_FSCK) {
318 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
319 retval = -EBUSY;
320 goto failed;
321 }
322
323 wait_time = min(mmp_check_interval * 2 + 1,
324 mmp_check_interval + 60);
325
326 /* Print MMP interval if more than 20 secs. */
327 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
328 ext4_warning(sb, "MMP interval %u higher than expected, please"
329 " wait.\n", wait_time * 2);
330
331 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
332 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
333 retval = -ETIMEDOUT;
334 goto failed;
335 }
336
337 retval = read_mmp_block(sb, &bh, mmp_block);
338 if (retval)
339 goto failed;
340 mmp = (struct mmp_struct *)(bh->b_data);
341 if (seq != le32_to_cpu(mmp->mmp_seq)) {
342 dump_mmp_msg(sb, mmp,
343 "Device is already active on another node.");
344 retval = -EBUSY;
345 goto failed;
346 }
347
348skip:
349 /*
350 * write a new random sequence number.
351 */
352 seq = mmp_new_seq();
353 mmp->mmp_seq = cpu_to_le32(seq);
354
355 /*
356 * On mount / remount we are protected against fs freezing (by s_umount
357 * semaphore) and grabbing freeze protection upsets lockdep
358 */
359 retval = write_mmp_block_thawed(sb, bh);
360 if (retval)
361 goto failed;
362
363 /*
364 * wait for MMP interval and check mmp_seq.
365 */
366 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
367 ext4_warning(sb, "MMP startup interrupted, failing mount");
368 retval = -ETIMEDOUT;
369 goto failed;
370 }
371
372 retval = read_mmp_block(sb, &bh, mmp_block);
373 if (retval)
374 goto failed;
375 mmp = (struct mmp_struct *)(bh->b_data);
376 if (seq != le32_to_cpu(mmp->mmp_seq)) {
377 dump_mmp_msg(sb, mmp,
378 "Device is already active on another node.");
379 retval = -EBUSY;
380 goto failed;
381 }
382
383 EXT4_SB(sb)->s_mmp_bh = bh;
384
385 BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
386 snprintf(mmp->mmp_bdevname, sizeof(mmp->mmp_bdevname),
387 "%pg", bh->b_bdev);
388
389 /*
390 * Start a kernel thread to update the MMP block periodically.
391 */
392 EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s",
393 (int)sizeof(mmp->mmp_bdevname),
394 mmp->mmp_bdevname);
395 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
396 EXT4_SB(sb)->s_mmp_tsk = NULL;
397 ext4_warning(sb, "Unable to create kmmpd thread for %s.",
398 sb->s_id);
399 retval = -ENOMEM;
400 goto failed;
401 }
402
403 return 0;
404
405failed:
406 brelse(bh);
407 return retval;
408}