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