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