2 * Helper functions for multiple mount protection (MMP).
4 * Copyright (C) 2011 Whamcloud, Inc.
7 * This file may be redistributed under the terms of the GNU Library
8 * General Public License, version 2.
15 #ifndef _DEFAULT_SOURCE
16 #define _DEFAULT_SOURCE /* since glibc 2.20 _SVID_SOURCE is deprecated */
26 #include <sys/types.h>
30 #include "ext2fs/ext2_fs.h"
31 #include "ext2fs/ext2fs.h"
37 #if __GNUC_PREREQ (4, 6)
38 #pragma GCC diagnostic push
40 #pragma GCC diagnostic ignored "-Wunused-parameter"
44 errcode_t ext2fs_mmp_read(ext2_filsys fs, blk64_t mmp_blk, void *buf)
47 struct mmp_struct *mmp_cmp;
50 if ((mmp_blk <= fs->super->s_first_data_block) ||
51 (mmp_blk >= ext2fs_blocks_count(fs->super)))
52 return EXT2_ET_MMP_BAD_BLOCK;
54 /* ext2fs_open() reserves fd0,1,2 to avoid stdio collision, so checking
55 * mmp_fd <= 0 is OK to validate that the fd is valid. This opens its
56 * own fd to read the MMP block to ensure that it is using O_DIRECT,
57 * regardless of how the io_manager is doing reads, to avoid caching of
58 * the MMP block by the io_manager or the VM. It needs to be fresh. */
59 if (fs->mmp_fd <= 0) {
61 int flags = O_RDONLY | O_DIRECT;
64 * There is no reason for using O_DIRECT if we're working with
65 * regular file. Disabling it also avoids problems with
66 * alignment when the device of the host file system has sector
67 * size larger than blocksize of the fs we're working with.
69 if (stat(fs->device_name, &st) == 0 &&
73 fs->mmp_fd = open(fs->device_name, flags);
75 retval = EXT2_ET_MMP_OPEN_DIRECT;
80 if (fs->mmp_cmp == NULL) {
81 int align = ext2fs_get_dio_alignment(fs->mmp_fd);
83 retval = ext2fs_get_memalign(fs->blocksize, align,
89 if ((blk64_t) ext2fs_llseek(fs->mmp_fd, mmp_blk * fs->blocksize,
91 mmp_blk * fs->blocksize) {
92 retval = EXT2_ET_LLSEEK_FAILED;
96 if (read(fs->mmp_fd, fs->mmp_cmp, fs->blocksize) != fs->blocksize) {
97 retval = EXT2_ET_SHORT_READ;
101 mmp_cmp = fs->mmp_cmp;
103 if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
104 !ext2fs_mmp_csum_verify(fs, mmp_cmp))
105 retval = EXT2_ET_MMP_CSUM_INVALID;
107 #ifdef WORDS_BIGENDIAN
108 ext2fs_swap_mmp(mmp_cmp);
111 if (buf != NULL && buf != fs->mmp_cmp)
112 memcpy(buf, fs->mmp_cmp, fs->blocksize);
114 if (mmp_cmp->mmp_magic != EXT4_MMP_MAGIC) {
115 retval = EXT2_ET_MMP_MAGIC_INVALID;
122 return EXT2_ET_OP_NOT_SUPPORTED;
126 errcode_t ext2fs_mmp_write(ext2_filsys fs, blk64_t mmp_blk, void *buf)
129 struct mmp_struct *mmp_s = buf;
131 errcode_t retval = 0;
133 gettimeofday(&tv, 0);
134 mmp_s->mmp_time = tv.tv_sec;
135 fs->mmp_last_written = tv.tv_sec;
137 if (fs->super->s_mmp_block < fs->super->s_first_data_block ||
138 fs->super->s_mmp_block > ext2fs_blocks_count(fs->super))
139 return EXT2_ET_MMP_BAD_BLOCK;
141 #ifdef WORDS_BIGENDIAN
142 ext2fs_swap_mmp(mmp_s);
145 retval = ext2fs_mmp_csum_set(fs, mmp_s);
149 /* I was tempted to make this use O_DIRECT and the mmp_fd, but
150 * this caused no end of grief, while leaving it as-is works. */
151 retval = io_channel_write_blk64(fs->io, mmp_blk, -(int)sizeof(struct mmp_struct), buf);
153 #ifdef WORDS_BIGENDIAN
154 ext2fs_swap_mmp(mmp_s);
157 /* Make sure the block gets to disk quickly */
158 io_channel_flush(fs->io);
161 return EXT2_ET_OP_NOT_SUPPORTED;
166 #define srand(x) srandom(x)
167 #define rand() random()
170 unsigned ext2fs_mmp_new_seq(void)
175 unsigned long pid = getpid();
177 gettimeofday(&tv, 0);
178 pid = (pid >> 16) | ((pid & 0xFFFF) << 16);
179 srand(pid ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
181 gettimeofday(&tv, 0);
182 /* Crank the random number generator a few times */
183 for (new_seq = (tv.tv_sec ^ tv.tv_usec) & 0x1F; new_seq > 0; new_seq--)
188 } while (new_seq > EXT4_MMP_SEQ_MAX);
192 return EXT2_ET_OP_NOT_SUPPORTED;
197 static errcode_t ext2fs_mmp_reset(ext2_filsys fs)
199 struct mmp_struct *mmp_s = NULL;
200 errcode_t retval = 0;
202 if (fs->mmp_buf == NULL) {
203 retval = ext2fs_get_mem(fs->blocksize, &fs->mmp_buf);
208 memset(fs->mmp_buf, 0, fs->blocksize);
211 mmp_s->mmp_magic = EXT4_MMP_MAGIC;
212 mmp_s->mmp_seq = EXT4_MMP_SEQ_CLEAN;
214 #ifdef HAVE_GETHOSTNAME
215 gethostname((char *) mmp_s->mmp_nodename, sizeof(mmp_s->mmp_nodename));
217 mmp_s->mmp_nodename[0] = '\0';
219 strncpy((char *) mmp_s->mmp_bdevname, fs->device_name,
220 sizeof(mmp_s->mmp_bdevname));
222 mmp_s->mmp_check_interval = fs->super->s_mmp_update_interval;
223 if (mmp_s->mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
224 mmp_s->mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
226 retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
232 errcode_t ext2fs_mmp_update(ext2_filsys fs)
234 return ext2fs_mmp_update2(fs, 0);
237 errcode_t ext2fs_mmp_clear(ext2_filsys fs)
240 errcode_t retval = 0;
242 if (!(fs->flags & EXT2_FLAG_RW))
243 return EXT2_ET_RO_FILSYS;
245 retval = ext2fs_mmp_reset(fs);
249 return EXT2_ET_OP_NOT_SUPPORTED;
253 errcode_t ext2fs_mmp_init(ext2_filsys fs)
256 struct ext2_super_block *sb = fs->super;
260 if (sb->s_mmp_update_interval == 0)
261 sb->s_mmp_update_interval = EXT4_MMP_UPDATE_INTERVAL;
262 /* This is probably excessively large, but who knows? */
263 else if (sb->s_mmp_update_interval > EXT4_MMP_MAX_UPDATE_INTERVAL)
264 return EXT2_ET_INVALID_ARGUMENT;
266 if (fs->mmp_buf == NULL) {
267 retval = ext2fs_get_mem(fs->blocksize, &fs->mmp_buf);
272 retval = ext2fs_alloc_block2(fs, 0, fs->mmp_buf, &mmp_block);
276 sb->s_mmp_block = mmp_block;
278 retval = ext2fs_mmp_reset(fs);
285 return EXT2_ET_OP_NOT_SUPPORTED;
290 #define min(x, y) ((x) < (y) ? (x) : (y))
294 * Make sure that the fs is not mounted or being fsck'ed while opening the fs.
296 errcode_t ext2fs_mmp_start(ext2_filsys fs)
299 struct mmp_struct *mmp_s;
301 unsigned int mmp_check_interval;
302 errcode_t retval = 0;
304 if (fs->mmp_buf == NULL) {
305 retval = ext2fs_get_mem(fs->blocksize, &fs->mmp_buf);
310 retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, fs->mmp_buf);
316 mmp_check_interval = fs->super->s_mmp_update_interval;
317 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
318 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
320 seq = mmp_s->mmp_seq;
321 if (seq == EXT4_MMP_SEQ_CLEAN)
323 if (seq == EXT4_MMP_SEQ_FSCK) {
324 retval = EXT2_ET_MMP_FSCK_ON;
328 if (seq > EXT4_MMP_SEQ_FSCK) {
329 retval = EXT2_ET_MMP_UNKNOWN_SEQ;
334 * If check_interval in MMP block is larger, use that instead of
335 * check_interval from the superblock.
337 if (mmp_s->mmp_check_interval > mmp_check_interval)
338 mmp_check_interval = mmp_s->mmp_check_interval;
340 sleep(min(mmp_check_interval * 2 + 1, mmp_check_interval + 60));
342 retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, fs->mmp_buf);
346 if (seq != mmp_s->mmp_seq) {
347 retval = EXT2_ET_MMP_FAILED;
352 if (!(fs->flags & EXT2_FLAG_RW))
355 mmp_s->mmp_seq = seq = ext2fs_mmp_new_seq();
356 #ifdef HAVE_GETHOSTNAME
357 gethostname((char *) mmp_s->mmp_nodename, sizeof(mmp_s->mmp_nodename));
359 strcpy((char *) mmp_s->mmp_nodename, "unknown host");
361 strncpy((char *) mmp_s->mmp_bdevname, fs->device_name,
362 sizeof(mmp_s->mmp_bdevname));
364 retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
368 sleep(min(2 * mmp_check_interval + 1, mmp_check_interval + 60));
370 retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, fs->mmp_buf);
374 if (seq != mmp_s->mmp_seq) {
375 retval = EXT2_ET_MMP_FAILED;
379 mmp_s->mmp_seq = EXT4_MMP_SEQ_FSCK;
380 retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
389 return EXT2_ET_OP_NOT_SUPPORTED;
394 * Clear the MMP usage in the filesystem. If this function returns an
395 * error EXT2_ET_MMP_CHANGE_ABORT it means the filesystem was modified
396 * by some other process while in use, and changes should be dropped, or
397 * risk filesystem corruption.
399 errcode_t ext2fs_mmp_stop(ext2_filsys fs)
402 struct mmp_struct *mmp, *mmp_cmp;
403 errcode_t retval = 0;
405 if (!ext2fs_has_feature_mmp(fs->super) ||
406 !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP) ||
407 (fs->mmp_buf == NULL) || (fs->mmp_cmp == NULL))
410 retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, NULL);
414 /* Check if the MMP block is not changed. */
416 mmp_cmp = fs->mmp_cmp;
417 if (memcmp(mmp, mmp_cmp, sizeof(*mmp_cmp))) {
418 retval = EXT2_ET_MMP_CHANGE_ABORT;
422 mmp_cmp->mmp_seq = EXT4_MMP_SEQ_CLEAN;
423 retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_cmp);
426 if (fs->mmp_fd > 0) {
433 if (!ext2fs_has_feature_mmp(fs->super) ||
434 !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP))
437 return EXT2_ET_OP_NOT_SUPPORTED;
441 #define EXT2_MIN_MMP_UPDATE_INTERVAL 60
444 * Update the on-disk mmp buffer, after checking that it hasn't been changed.
446 errcode_t ext2fs_mmp_update2(ext2_filsys fs, int immediately)
449 struct mmp_struct *mmp, *mmp_cmp;
451 errcode_t retval = 0;
453 if (!ext2fs_has_feature_mmp(fs->super) ||
454 !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP))
457 gettimeofday(&tv, 0);
459 tv.tv_sec - fs->mmp_last_written < EXT2_MIN_MMP_UPDATE_INTERVAL)
462 retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, NULL);
467 mmp_cmp = fs->mmp_cmp;
469 if (memcmp(mmp, mmp_cmp, sizeof(*mmp_cmp)))
470 return EXT2_ET_MMP_CHANGE_ABORT;
472 mmp->mmp_time = tv.tv_sec;
473 mmp->mmp_seq = EXT4_MMP_SEQ_FSCK;
474 retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
479 if (!ext2fs_has_feature_mmp(fs->super) ||
480 !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP))
483 return EXT2_ET_OP_NOT_SUPPORTED;
486 #if __GNUC_PREREQ (4, 6)
487 #pragma GCC diagnostic pop