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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 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 "
124 "node: %s, last update device: %s",
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(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 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(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(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_rdonly(sb))
189 break;
190
191 diff = jiffies - last_update_time;
192 if (diff < mmp_update_interval * HZ)
193 schedule_timeout_interruptible(mmp_update_interval *
194 HZ - diff);
195
196 /*
197 * We need to make sure that more than mmp_check_interval
198 * seconds have not passed since writing. If that has happened
199 * we need to check if the MMP block is as we left it.
200 */
201 diff = jiffies - last_update_time;
202 if (diff > mmp_check_interval * HZ) {
203 struct buffer_head *bh_check = NULL;
204 struct mmp_struct *mmp_check;
205
206 retval = read_mmp_block(sb, &bh_check, mmp_block);
207 if (retval) {
208 ext4_error(sb, "error reading MMP data: %d",
209 retval);
210 goto exit_thread;
211 }
212
213 mmp_check = (struct mmp_struct *)(bh_check->b_data);
214 if (mmp->mmp_seq != mmp_check->mmp_seq ||
215 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
216 sizeof(mmp->mmp_nodename))) {
217 dump_mmp_msg(sb, mmp_check,
218 "Error while updating MMP info. "
219 "The filesystem seems to have been"
220 " multiply mounted.");
221 ext4_error(sb, "abort");
222 put_bh(bh_check);
223 retval = -EBUSY;
224 goto exit_thread;
225 }
226 put_bh(bh_check);
227 }
228
229 /*
230 * Adjust the mmp_check_interval depending on how much time
231 * it took for the MMP block to be written.
232 */
233 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
234 EXT4_MMP_MAX_CHECK_INTERVAL),
235 EXT4_MMP_MIN_CHECK_INTERVAL);
236 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
237 }
238
239 /*
240 * Unmount seems to be clean.
241 */
242 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
243 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
244
245 retval = write_mmp_block(sb, bh);
246
247exit_thread:
248 EXT4_SB(sb)->s_mmp_tsk = NULL;
249 kfree(data);
250 brelse(bh);
251 return retval;
252}
253
254/*
255 * Get a random new sequence number but make sure it is not greater than
256 * EXT4_MMP_SEQ_MAX.
257 */
258static unsigned int mmp_new_seq(void)
259{
260 u32 new_seq;
261
262 do {
263 new_seq = prandom_u32();
264 } while (new_seq > EXT4_MMP_SEQ_MAX);
265
266 return new_seq;
267}
268
269/*
270 * Protect the filesystem from being mounted more than once.
271 */
272int ext4_multi_mount_protect(struct super_block *sb,
273 ext4_fsblk_t mmp_block)
274{
275 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
276 struct buffer_head *bh = NULL;
277 struct mmp_struct *mmp = NULL;
278 struct mmpd_data *mmpd_data;
279 u32 seq;
280 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
281 unsigned int wait_time = 0;
282 int retval;
283
284 if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
285 mmp_block >= ext4_blocks_count(es)) {
286 ext4_warning(sb, "Invalid MMP block in superblock");
287 goto failed;
288 }
289
290 retval = read_mmp_block(sb, &bh, mmp_block);
291 if (retval)
292 goto failed;
293
294 mmp = (struct mmp_struct *)(bh->b_data);
295
296 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
297 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
298
299 /*
300 * If check_interval in MMP block is larger, use that instead of
301 * update_interval from the superblock.
302 */
303 if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
304 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
305
306 seq = le32_to_cpu(mmp->mmp_seq);
307 if (seq == EXT4_MMP_SEQ_CLEAN)
308 goto skip;
309
310 if (seq == EXT4_MMP_SEQ_FSCK) {
311 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
312 goto failed;
313 }
314
315 wait_time = min(mmp_check_interval * 2 + 1,
316 mmp_check_interval + 60);
317
318 /* Print MMP interval if more than 20 secs. */
319 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
320 ext4_warning(sb, "MMP interval %u higher than expected, please"
321 " wait.\n", wait_time * 2);
322
323 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
324 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
325 goto failed;
326 }
327
328 retval = read_mmp_block(sb, &bh, mmp_block);
329 if (retval)
330 goto failed;
331 mmp = (struct mmp_struct *)(bh->b_data);
332 if (seq != le32_to_cpu(mmp->mmp_seq)) {
333 dump_mmp_msg(sb, mmp,
334 "Device is already active on another node.");
335 goto failed;
336 }
337
338skip:
339 /*
340 * write a new random sequence number.
341 */
342 seq = mmp_new_seq();
343 mmp->mmp_seq = cpu_to_le32(seq);
344
345 retval = write_mmp_block(sb, bh);
346 if (retval)
347 goto failed;
348
349 /*
350 * wait for MMP interval and check mmp_seq.
351 */
352 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
353 ext4_warning(sb, "MMP startup interrupted, failing mount");
354 goto failed;
355 }
356
357 retval = read_mmp_block(sb, &bh, mmp_block);
358 if (retval)
359 goto failed;
360 mmp = (struct mmp_struct *)(bh->b_data);
361 if (seq != le32_to_cpu(mmp->mmp_seq)) {
362 dump_mmp_msg(sb, mmp,
363 "Device is already active on another node.");
364 goto failed;
365 }
366
367 mmpd_data = kmalloc(sizeof(*mmpd_data), GFP_KERNEL);
368 if (!mmpd_data) {
369 ext4_warning(sb, "not enough memory for mmpd_data");
370 goto failed;
371 }
372 mmpd_data->sb = sb;
373 mmpd_data->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, mmpd_data, "kmmpd-%s",
379 bdevname(bh->b_bdev,
380 mmp->mmp_bdevname));
381 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
382 EXT4_SB(sb)->s_mmp_tsk = NULL;
383 kfree(mmpd_data);
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}
395
396