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