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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
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
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 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(REQ_OP_READ, 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 node: %.*s, last update device: %.*s",
124 (unsigned long long)le64_to_cpu(mmp->mmp_time),
125 (int)sizeof(mmp->mmp_nodename), mmp->mmp_nodename,
126 (int)sizeof(mmp->mmp_bdevname), 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(ktime_get_real_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 BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
158 bdevname(bh->b_bdev, mmp->mmp_bdevname);
159
160 memcpy(mmp->mmp_nodename, init_utsname()->nodename,
161 sizeof(mmp->mmp_nodename));
162
163 while (!kthread_should_stop()) {
164 if (++seq > EXT4_MMP_SEQ_MAX)
165 seq = 1;
166
167 mmp->mmp_seq = cpu_to_le32(seq);
168 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
169 last_update_time = jiffies;
170
171 retval = write_mmp_block(sb, bh);
172 /*
173 * Don't spew too many error messages. Print one every
174 * (s_mmp_update_interval * 60) seconds.
175 */
176 if (retval) {
177 if ((failed_writes % 60) == 0) {
178 ext4_error_err(sb, -retval,
179 "Error writing to MMP block");
180 }
181 failed_writes++;
182 }
183
184 if (!(le32_to_cpu(es->s_feature_incompat) &
185 EXT4_FEATURE_INCOMPAT_MMP)) {
186 ext4_warning(sb, "kmmpd being stopped since MMP feature"
187 " has been disabled.");
188 goto exit_thread;
189 }
190
191 if (sb_rdonly(sb))
192 break;
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_err(sb, -retval,
212 "error reading MMP data: %d",
213 retval);
214 goto exit_thread;
215 }
216
217 mmp_check = (struct mmp_struct *)(bh_check->b_data);
218 if (mmp->mmp_seq != mmp_check->mmp_seq ||
219 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
220 sizeof(mmp->mmp_nodename))) {
221 dump_mmp_msg(sb, mmp_check,
222 "Error while updating MMP info. "
223 "The filesystem seems to have been"
224 " multiply mounted.");
225 ext4_error_err(sb, EBUSY, "abort");
226 put_bh(bh_check);
227 retval = -EBUSY;
228 goto exit_thread;
229 }
230 put_bh(bh_check);
231 }
232
233 /*
234 * Adjust the mmp_check_interval depending on how much time
235 * it took for the MMP block to be written.
236 */
237 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
238 EXT4_MMP_MAX_CHECK_INTERVAL),
239 EXT4_MMP_MIN_CHECK_INTERVAL);
240 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
241 }
242
243 /*
244 * Unmount seems to be clean.
245 */
246 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
247 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
248
249 retval = write_mmp_block(sb, bh);
250
251exit_thread:
252 EXT4_SB(sb)->s_mmp_tsk = NULL;
253 kfree(data);
254 brelse(bh);
255 return retval;
256}
257
258/*
259 * Get a random new sequence number but make sure it is not greater than
260 * EXT4_MMP_SEQ_MAX.
261 */
262static unsigned int mmp_new_seq(void)
263{
264 u32 new_seq;
265
266 do {
267 new_seq = prandom_u32();
268 } while (new_seq > EXT4_MMP_SEQ_MAX);
269
270 return new_seq;
271}
272
273/*
274 * Protect the filesystem from being mounted more than once.
275 */
276int ext4_multi_mount_protect(struct super_block *sb,
277 ext4_fsblk_t mmp_block)
278{
279 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
280 struct buffer_head *bh = NULL;
281 struct mmp_struct *mmp = NULL;
282 struct mmpd_data *mmpd_data;
283 u32 seq;
284 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
285 unsigned int wait_time = 0;
286 int retval;
287
288 if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
289 mmp_block >= ext4_blocks_count(es)) {
290 ext4_warning(sb, "Invalid MMP block in superblock");
291 goto failed;
292 }
293
294 retval = read_mmp_block(sb, &bh, mmp_block);
295 if (retval)
296 goto failed;
297
298 mmp = (struct mmp_struct *)(bh->b_data);
299
300 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
301 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
302
303 /*
304 * If check_interval in MMP block is larger, use that instead of
305 * update_interval from the superblock.
306 */
307 if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
308 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
309
310 seq = le32_to_cpu(mmp->mmp_seq);
311 if (seq == EXT4_MMP_SEQ_CLEAN)
312 goto skip;
313
314 if (seq == EXT4_MMP_SEQ_FSCK) {
315 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
316 goto failed;
317 }
318
319 wait_time = min(mmp_check_interval * 2 + 1,
320 mmp_check_interval + 60);
321
322 /* Print MMP interval if more than 20 secs. */
323 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
324 ext4_warning(sb, "MMP interval %u higher than expected, please"
325 " wait.\n", wait_time * 2);
326
327 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
328 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
329 goto failed;
330 }
331
332 retval = read_mmp_block(sb, &bh, mmp_block);
333 if (retval)
334 goto failed;
335 mmp = (struct mmp_struct *)(bh->b_data);
336 if (seq != le32_to_cpu(mmp->mmp_seq)) {
337 dump_mmp_msg(sb, mmp,
338 "Device is already active on another node.");
339 goto failed;
340 }
341
342skip:
343 /*
344 * write a new random sequence number.
345 */
346 seq = mmp_new_seq();
347 mmp->mmp_seq = cpu_to_le32(seq);
348
349 retval = write_mmp_block(sb, bh);
350 if (retval)
351 goto failed;
352
353 /*
354 * wait for MMP interval and check mmp_seq.
355 */
356 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
357 ext4_warning(sb, "MMP startup interrupted, failing mount");
358 goto failed;
359 }
360
361 retval = read_mmp_block(sb, &bh, mmp_block);
362 if (retval)
363 goto failed;
364 mmp = (struct mmp_struct *)(bh->b_data);
365 if (seq != le32_to_cpu(mmp->mmp_seq)) {
366 dump_mmp_msg(sb, mmp,
367 "Device is already active on another node.");
368 goto failed;
369 }
370
371 mmpd_data = kmalloc(sizeof(*mmpd_data), GFP_KERNEL);
372 if (!mmpd_data) {
373 ext4_warning(sb, "not enough memory for mmpd_data");
374 goto failed;
375 }
376 mmpd_data->sb = sb;
377 mmpd_data->bh = bh;
378
379 /*
380 * Start a kernel thread to update the MMP block periodically.
381 */
382 EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%.*s",
383 (int)sizeof(mmp->mmp_bdevname),
384 bdevname(bh->b_bdev,
385 mmp->mmp_bdevname));
386 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
387 EXT4_SB(sb)->s_mmp_tsk = NULL;
388 kfree(mmpd_data);
389 ext4_warning(sb, "Unable to create kmmpd thread for %s.",
390 sb->s_id);
391 goto failed;
392 }
393
394 return 0;
395
396failed:
397 brelse(bh);
398 return 1;
399}
400
401