blob: 7ea4ba4eff2ac4b9dbcae63a54ee68bb5e1a7190 [file] [log] [blame]
Johann Lombardic5e06d12011-05-24 18:31:25 -04001#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
Nikitas Angelinas215fc6a2011-10-18 10:49:51 -0400112 memcpy(mmp->mmp_nodename, init_utsname()->nodename,
Johann Lombardic5e06d12011-05-24 18:31:25 -0400113 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 */
Nikitas Angelinasbdfc2302011-10-18 10:51:51 -0400128 if (retval) {
129 if ((failed_writes % 60) == 0)
130 ext4_error(sb, "Error writing to MMP block");
Johann Lombardic5e06d12011-05-24 18:31:25 -0400131 failed_writes++;
132 }
133
134 if (!(le32_to_cpu(es->s_feature_incompat) &
135 EXT4_FEATURE_INCOMPAT_MMP)) {
136 ext4_warning(sb, "kmmpd being stopped since MMP feature"
137 " has been disabled.");
138 EXT4_SB(sb)->s_mmp_tsk = NULL;
139 goto failed;
140 }
141
142 if (sb->s_flags & MS_RDONLY) {
143 ext4_warning(sb, "kmmpd being stopped since filesystem "
144 "has been remounted as readonly.");
145 EXT4_SB(sb)->s_mmp_tsk = NULL;
146 goto failed;
147 }
148
149 diff = jiffies - last_update_time;
150 if (diff < mmp_update_interval * HZ)
151 schedule_timeout_interruptible(mmp_update_interval *
152 HZ - diff);
153
154 /*
155 * We need to make sure that more than mmp_check_interval
156 * seconds have not passed since writing. If that has happened
157 * we need to check if the MMP block is as we left it.
158 */
159 diff = jiffies - last_update_time;
160 if (diff > mmp_check_interval * HZ) {
161 struct buffer_head *bh_check = NULL;
162 struct mmp_struct *mmp_check;
163
164 retval = read_mmp_block(sb, &bh_check, mmp_block);
165 if (retval) {
166 ext4_error(sb, "error reading MMP data: %d",
167 retval);
168
169 EXT4_SB(sb)->s_mmp_tsk = NULL;
170 goto failed;
171 }
172
173 mmp_check = (struct mmp_struct *)(bh_check->b_data);
174 if (mmp->mmp_seq != mmp_check->mmp_seq ||
175 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
176 sizeof(mmp->mmp_nodename))) {
177 dump_mmp_msg(sb, mmp_check,
178 "Error while updating MMP info. "
179 "The filesystem seems to have been"
180 " multiply mounted.");
181 ext4_error(sb, "abort");
182 goto failed;
183 }
184 put_bh(bh_check);
185 }
186
187 /*
188 * Adjust the mmp_check_interval depending on how much time
189 * it took for the MMP block to be written.
190 */
191 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
192 EXT4_MMP_MAX_CHECK_INTERVAL),
193 EXT4_MMP_MIN_CHECK_INTERVAL);
194 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
195 }
196
197 /*
198 * Unmount seems to be clean.
199 */
200 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
201 mmp->mmp_time = cpu_to_le64(get_seconds());
202
203 retval = write_mmp_block(bh);
204
205failed:
206 kfree(data);
207 brelse(bh);
208 return retval;
209}
210
211/*
212 * Get a random new sequence number but make sure it is not greater than
213 * EXT4_MMP_SEQ_MAX.
214 */
215static unsigned int mmp_new_seq(void)
216{
217 u32 new_seq;
218
219 do {
220 get_random_bytes(&new_seq, sizeof(u32));
221 } while (new_seq > EXT4_MMP_SEQ_MAX);
222
223 return new_seq;
224}
225
226/*
227 * Protect the filesystem from being mounted more than once.
228 */
229int ext4_multi_mount_protect(struct super_block *sb,
230 ext4_fsblk_t mmp_block)
231{
232 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
233 struct buffer_head *bh = NULL;
234 struct mmp_struct *mmp = NULL;
235 struct mmpd_data *mmpd_data;
236 u32 seq;
237 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
238 unsigned int wait_time = 0;
239 int retval;
240
241 if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
242 mmp_block >= ext4_blocks_count(es)) {
243 ext4_warning(sb, "Invalid MMP block in superblock");
244 goto failed;
245 }
246
247 retval = read_mmp_block(sb, &bh, mmp_block);
248 if (retval)
249 goto failed;
250
251 mmp = (struct mmp_struct *)(bh->b_data);
252
253 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
254 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
255
256 /*
257 * If check_interval in MMP block is larger, use that instead of
258 * update_interval from the superblock.
259 */
260 if (mmp->mmp_check_interval > mmp_check_interval)
261 mmp_check_interval = mmp->mmp_check_interval;
262
263 seq = le32_to_cpu(mmp->mmp_seq);
264 if (seq == EXT4_MMP_SEQ_CLEAN)
265 goto skip;
266
267 if (seq == EXT4_MMP_SEQ_FSCK) {
268 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
269 goto failed;
270 }
271
272 wait_time = min(mmp_check_interval * 2 + 1,
273 mmp_check_interval + 60);
274
275 /* Print MMP interval if more than 20 secs. */
276 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
277 ext4_warning(sb, "MMP interval %u higher than expected, please"
278 " wait.\n", wait_time * 2);
279
280 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
281 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
282 goto failed;
283 }
284
285 retval = read_mmp_block(sb, &bh, mmp_block);
286 if (retval)
287 goto failed;
288 mmp = (struct mmp_struct *)(bh->b_data);
289 if (seq != le32_to_cpu(mmp->mmp_seq)) {
290 dump_mmp_msg(sb, mmp,
291 "Device is already active on another node.");
292 goto failed;
293 }
294
295skip:
296 /*
297 * write a new random sequence number.
298 */
Darrick J. Wongf6f96fd2011-10-18 10:53:51 -0400299 seq = mmp_new_seq();
300 mmp->mmp_seq = cpu_to_le32(seq);
Johann Lombardic5e06d12011-05-24 18:31:25 -0400301
302 retval = write_mmp_block(bh);
303 if (retval)
304 goto failed;
305
306 /*
307 * wait for MMP interval and check mmp_seq.
308 */
309 if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
310 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
311 goto failed;
312 }
313
314 retval = read_mmp_block(sb, &bh, mmp_block);
315 if (retval)
316 goto failed;
317 mmp = (struct mmp_struct *)(bh->b_data);
318 if (seq != le32_to_cpu(mmp->mmp_seq)) {
319 dump_mmp_msg(sb, mmp,
320 "Device is already active on another node.");
321 goto failed;
322 }
323
324 mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
325 if (!mmpd_data) {
326 ext4_warning(sb, "not enough memory for mmpd_data");
327 goto failed;
328 }
329 mmpd_data->sb = sb;
330 mmpd_data->bh = bh;
331
332 /*
333 * Start a kernel thread to update the MMP block periodically.
334 */
335 EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
336 bdevname(bh->b_bdev,
337 mmp->mmp_bdevname));
338 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
339 EXT4_SB(sb)->s_mmp_tsk = NULL;
340 kfree(mmpd_data);
341 ext4_warning(sb, "Unable to create kmmpd thread for %s.",
342 sb->s_id);
343 goto failed;
344 }
345
346 return 0;
347
348failed:
349 brelse(bh);
350 return 1;
351}
352
353