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