[linux-2.6-block.git] / fs / ext4 / mmp.c

#include <linux/fs.h>
#include <linux/random.h>
#include <linux/buffer_head.h>
#include <linux/utsname.h>
#include <linux/kthread.h>

#include "ext4.h"

/* Checksumming functions */
static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	int offset = offsetof(struct mmp_struct, mmp_checksum);
	__u32 csum;

	csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);

	return cpu_to_le32(csum);
}

static int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
{
	if (!ext4_has_metadata_csum(sb))
		return 1;

	return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
}

static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
{
	if (!ext4_has_metadata_csum(sb))
		return;

	mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
}

/*
 * Write the MMP block using WRITE_SYNC to try to get the block on-disk
 * faster.
 */
static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
{
	struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);

	/*
	 * We protect against freezing so that we don't create dirty buffers
	 * on frozen filesystem.
	 */
	sb_start_write(sb);
	ext4_mmp_csum_set(sb, mmp);
	mark_buffer_dirty(bh);
	lock_buffer(bh);
	bh->b_end_io = end_buffer_write_sync;
	get_bh(bh);
	submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh);
	wait_on_buffer(bh);
	sb_end_write(sb);
	if (unlikely(!buffer_uptodate(bh)))
		return 1;

	return 0;
}

/*
 * Read the MMP block. It _must_ be read from disk and hence we clear the
 * uptodate flag on the buffer.
 */
static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
			  ext4_fsblk_t mmp_block)
{
	struct mmp_struct *mmp;

	if (*bh)
		clear_buffer_uptodate(*bh);

	/* This would be sb_bread(sb, mmp_block), except we need to be sure
	 * that the MD RAID device cache has been bypassed, and that the read
	 * is not blocked in the elevator. */
	if (!*bh)
		*bh = sb_getblk(sb, mmp_block);
	if (!*bh)
		return -ENOMEM;
	if (*bh) {
		get_bh(*bh);
		lock_buffer(*bh);
		(*bh)->b_end_io = end_buffer_read_sync;
		submit_bh(READ_SYNC | REQ_META | REQ_PRIO, *bh);
		wait_on_buffer(*bh);
		if (!buffer_uptodate(*bh)) {
			brelse(*bh);
			*bh = NULL;
		}
	}
	if (unlikely(!*bh)) {
		ext4_warning(sb, "Error while reading MMP block %llu",
			     mmp_block);
		return -EIO;
	}

	mmp = (struct mmp_struct *)((*bh)->b_data);
	if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC ||
	    !ext4_mmp_csum_verify(sb, mmp))
		return -EINVAL;

	return 0;
}

/*
 * Dump as much information as possible to help the admin.
 */
void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
		    const char *function, unsigned int line, const char *msg)
{
	__ext4_warning(sb, function, line, msg);
	__ext4_warning(sb, function, line,
		       "MMP failure info: last update time: %llu, last update "
		       "node: %s, last update device: %s\n",
		       (long long unsigned int) le64_to_cpu(mmp->mmp_time),
		       mmp->mmp_nodename, mmp->mmp_bdevname);
}

/*
 * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
 */
static int kmmpd(void *data)
{
	struct super_block *sb = ((struct mmpd_data *) data)->sb;
	struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	struct mmp_struct *mmp;
	ext4_fsblk_t mmp_block;
	u32 seq = 0;
	unsigned long failed_writes = 0;
	int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
	unsigned mmp_check_interval;
	unsigned long last_update_time;
	unsigned long diff;
	int retval;

	mmp_block = le64_to_cpu(es->s_mmp_block);
	mmp = (struct mmp_struct *)(bh->b_data);
	mmp->mmp_time = cpu_to_le64(get_seconds());
	/*
	 * Start with the higher mmp_check_interval and reduce it if
	 * the MMP block is being updated on time.
	 */
	mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
				 EXT4_MMP_MIN_CHECK_INTERVAL);
	mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
	bdevname(bh->b_bdev, mmp->mmp_bdevname);

	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
	       sizeof(mmp->mmp_nodename));

	while (!kthread_should_stop()) {
		if (++seq > EXT4_MMP_SEQ_MAX)
			seq = 1;

		mmp->mmp_seq = cpu_to_le32(seq);
		mmp->mmp_time = cpu_to_le64(get_seconds());
		last_update_time = jiffies;

		retval = write_mmp_block(sb, bh);
		/*
		 * Don't spew too many error messages. Print one every
		 * (s_mmp_update_interval * 60) seconds.
		 */
		if (retval) {
			if ((failed_writes % 60) == 0)
				ext4_error(sb, "Error writing to MMP block");
			failed_writes++;
		}

		if (!(le32_to_cpu(es->s_feature_incompat) &
		    EXT4_FEATURE_INCOMPAT_MMP)) {
			ext4_warning(sb, "kmmpd being stopped since MMP feature"
				     " has been disabled.");
			EXT4_SB(sb)->s_mmp_tsk = NULL;
			goto failed;
		}

		if (sb->s_flags & MS_RDONLY) {
			ext4_warning(sb, "kmmpd being stopped since filesystem "
				     "has been remounted as readonly.");
			EXT4_SB(sb)->s_mmp_tsk = NULL;
			goto failed;
		}

		diff = jiffies - last_update_time;
		if (diff < mmp_update_interval * HZ)
			schedule_timeout_interruptible(mmp_update_interval *
						       HZ - diff);

		/*
		 * We need to make sure that more than mmp_check_interval
		 * seconds have not passed since writing. If that has happened
		 * we need to check if the MMP block is as we left it.
		 */
		diff = jiffies - last_update_time;
		if (diff > mmp_check_interval * HZ) {
			struct buffer_head *bh_check = NULL;
			struct mmp_struct *mmp_check;

			retval = read_mmp_block(sb, &bh_check, mmp_block);
			if (retval) {
				ext4_error(sb, "error reading MMP data: %d",
					   retval);

				EXT4_SB(sb)->s_mmp_tsk = NULL;
				goto failed;
			}

			mmp_check = (struct mmp_struct *)(bh_check->b_data);
			if (mmp->mmp_seq != mmp_check->mmp_seq ||
			    memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
				   sizeof(mmp->mmp_nodename))) {
				dump_mmp_msg(sb, mmp_check,
					     "Error while updating MMP info. "
					     "The filesystem seems to have been"
					     " multiply mounted.");
				ext4_error(sb, "abort");
				goto failed;
			}
			put_bh(bh_check);
		}

		 /*
		 * Adjust the mmp_check_interval depending on how much time
		 * it took for the MMP block to be written.
		 */
		mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
					     EXT4_MMP_MAX_CHECK_INTERVAL),
					 EXT4_MMP_MIN_CHECK_INTERVAL);
		mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
	}

	/*
	 * Unmount seems to be clean.
	 */
	mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
	mmp->mmp_time = cpu_to_le64(get_seconds());

	retval = write_mmp_block(sb, bh);

failed:
	kfree(data);
	brelse(bh);
	return retval;
}

/*
 * Get a random new sequence number but make sure it is not greater than
 * EXT4_MMP_SEQ_MAX.
 */
static unsigned int mmp_new_seq(void)
{
	u32 new_seq;

	do {
		new_seq = prandom_u32();
	} while (new_seq > EXT4_MMP_SEQ_MAX);

	return new_seq;
}

/*
 * Protect the filesystem from being mounted more than once.
 */
int ext4_multi_mount_protect(struct super_block *sb,
				    ext4_fsblk_t mmp_block)
{
	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	struct buffer_head *bh = NULL;
	struct mmp_struct *mmp = NULL;
	struct mmpd_data *mmpd_data;
	u32 seq;
	unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
	unsigned int wait_time = 0;
	int retval;

	if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
	    mmp_block >= ext4_blocks_count(es)) {
		ext4_warning(sb, "Invalid MMP block in superblock");
		goto failed;
	}

	retval = read_mmp_block(sb, &bh, mmp_block);
	if (retval)
		goto failed;

	mmp = (struct mmp_struct *)(bh->b_data);

	if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
		mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;

	/*
	 * If check_interval in MMP block is larger, use that instead of
	 * update_interval from the superblock.
	 */
	if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
		mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);

	seq = le32_to_cpu(mmp->mmp_seq);
	if (seq == EXT4_MMP_SEQ_CLEAN)
		goto skip;

	if (seq == EXT4_MMP_SEQ_FSCK) {
		dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
		goto failed;
	}

	wait_time = min(mmp_check_interval * 2 + 1,
			mmp_check_interval + 60);

	/* Print MMP interval if more than 20 secs. */
	if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
		ext4_warning(sb, "MMP interval %u higher than expected, please"
			     " wait.\n", wait_time * 2);

	if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
		ext4_warning(sb, "MMP startup interrupted, failing mount\n");
		goto failed;
	}

	retval = read_mmp_block(sb, &bh, mmp_block);
	if (retval)
		goto failed;
	mmp = (struct mmp_struct *)(bh->b_data);
	if (seq != le32_to_cpu(mmp->mmp_seq)) {
		dump_mmp_msg(sb, mmp,
			     "Device is already active on another node.");
		goto failed;
	}

skip:
	/*
	 * write a new random sequence number.
	 */
	seq = mmp_new_seq();
	mmp->mmp_seq = cpu_to_le32(seq);

	retval = write_mmp_block(sb, bh);
	if (retval)
		goto failed;

	/*
	 * wait for MMP interval and check mmp_seq.
	 */
	if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
		ext4_warning(sb, "MMP startup interrupted, failing mount\n");
		goto failed;
	}

	retval = read_mmp_block(sb, &bh, mmp_block);
	if (retval)
		goto failed;
	mmp = (struct mmp_struct *)(bh->b_data);
	if (seq != le32_to_cpu(mmp->mmp_seq)) {
		dump_mmp_msg(sb, mmp,
			     "Device is already active on another node.");
		goto failed;
	}

	mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
	if (!mmpd_data) {
		ext4_warning(sb, "not enough memory for mmpd_data");
		goto failed;
	}
	mmpd_data->sb = sb;
	mmpd_data->bh = bh;

	/*
	 * Start a kernel thread to update the MMP block periodically.
	 */
	EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
					     bdevname(bh->b_bdev,
						      mmp->mmp_bdevname));
	if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
		EXT4_SB(sb)->s_mmp_tsk = NULL;
		kfree(mmpd_data);
		ext4_warning(sb, "Unable to create kmmpd thread for %s.",
			     sb->s_id);
		goto failed;
	}

	return 0;

failed:
	brelse(bh);
	return 1;
}
Commit	Line	Data
c5e06d10 JL	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
5c359a47	9	/* Checksumming functions */
171a7f21	10	static __le32 ext4_mmp_csum(struct super_block sb, struct mmp_struct mmp)
5c359a47 DW	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
c197855e	21	static int ext4_mmp_csum_verify(struct super_block sb, struct mmp_struct mmp)
5c359a47	22	{
9aa5d32b	23	if (!ext4_has_metadata_csum(sb))
5c359a47 DW	24	return 1;
	25
	26	return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
	27	}
	28
c197855e	29	static void ext4_mmp_csum_set(struct super_block sb, struct mmp_struct mmp)
5c359a47	30	{
9aa5d32b	31	if (!ext4_has_metadata_csum(sb))
5c359a47 DW	32	return;
	33
	34	mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
	35	}
	36
c5e06d10 JL	37	/*
	38	* Write the MMP block using WRITE_SYNC to try to get the block on-disk
	39	* faster.
	40	*/
5c359a47	41	static int write_mmp_block(struct super_block sb, struct buffer_head bh)
c5e06d10	42	{
5c359a47 DW	43	struct mmp_struct mmp = (struct mmp_struct )(bh->b_data);
5c359a47 DW	44
8e8ad8a5 JK	45	/*
	46	* We protect against freezing so that we don't create dirty buffers
	47	* on frozen filesystem.
	48	*/
	49	sb_start_write(sb);
5c359a47	50	ext4_mmp_csum_set(sb, mmp);
c5e06d10 JL	51	mark_buffer_dirty(bh);
	52	lock_buffer(bh);
	53	bh->b_end_io = end_buffer_write_sync;
	54	get_bh(bh);
9f203507	55	submit_bh(WRITE_SYNC \| REQ_META \| REQ_PRIO, bh);
c5e06d10	56	wait_on_buffer(bh);
8e8ad8a5	57	sb_end_write(sb);
c5e06d10 JL	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	*/
	68	static 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
	73	if (*bh)
	74	clear_buffer_uptodate(*bh);
	75
	76	/* This would be sb_bread(sb, mmp_block), except we need to be sure
	77	* that the MD RAID device cache has been bypassed, and that the read
	78	* is not blocked in the elevator. */
	79	if (!*bh)
	80	*bh = sb_getblk(sb, mmp_block);
860d21e2 TT	81	if (!*bh)
860d21e2 TT	82	return -ENOMEM;
c5e06d10 JL	83	if (*bh) {
	84	get_bh(*bh);
	85	lock_buffer(*bh);
	86	(*bh)->b_end_io = end_buffer_read_sync;
9f203507	87	submit_bh(READ_SYNC \| REQ_META \| REQ_PRIO, *bh);
c5e06d10 JL	88	wait_on_buffer(*bh);
	89	if (!buffer_uptodate(*bh)) {
	90	brelse(*bh);
	91	*bh = NULL;
	92	}
	93	}
aebf0243	94	if (unlikely(!*bh)) {
c5e06d10 JL	95	ext4_warning(sb, "Error while reading MMP block %llu",
	96	mmp_block);
	97	return -EIO;
	98	}
	99
	100	mmp = (struct mmp_struct )((bh)->b_data);
5c359a47 DW	101	if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC \|\|
5c359a47 DW	102	!ext4_mmp_csum_verify(sb, mmp))
c5e06d10 JL	103	return -EINVAL;
	104
	105	return 0;
	106	}
	107
	108	/*
	109	* Dump as much information as possible to help the admin.
	110	*/
	111	void __dump_mmp_msg(struct super_block sb, struct mmp_struct mmp,
	112	const char function, unsigned int line, const char msg)
	113	{
	114	__ext4_warning(sb, function, line, msg);
	115	__ext4_warning(sb, function, line,
	116	"MMP failure info: last update time: %llu, last update "
	117	"node: %s, last update device: %s\n",
	118	(long long unsigned int) le64_to_cpu(mmp->mmp_time),
	119	mmp->mmp_nodename, mmp->mmp_bdevname);
	120	}
	121
	122	/*
	123	* kmmpd will update the MMP sequence every s_mmp_update_interval seconds
	124	*/
	125	static int kmmpd(void *data)
	126	{
	127	struct super_block sb = ((struct mmpd_data ) data)->sb;
	128	struct buffer_head bh = ((struct mmpd_data ) data)->bh;
	129	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	130	struct mmp_struct *mmp;
	131	ext4_fsblk_t mmp_block;
	132	u32 seq = 0;
	133	unsigned long failed_writes = 0;
	134	int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
	135	unsigned mmp_check_interval;
	136	unsigned long last_update_time;
	137	unsigned long diff;
	138	int retval;
	139
	140	mmp_block = le64_to_cpu(es->s_mmp_block);
	141	mmp = (struct mmp_struct *)(bh->b_data);
	142	mmp->mmp_time = cpu_to_le64(get_seconds());
	143	/*
	144	* Start with the higher mmp_check_interval and reduce it if
	145	* the MMP block is being updated on time.
	146	*/
	147	mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
	148	EXT4_MMP_MIN_CHECK_INTERVAL);
	149	mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
	150	bdevname(bh->b_bdev, mmp->mmp_bdevname);
	151
215fc6af	152	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
c5e06d10 JL	153	sizeof(mmp->mmp_nodename));
	154
	155	while (!kthread_should_stop()) {
	156	if (++seq > EXT4_MMP_SEQ_MAX)
	157	seq = 1;
	158
	159	mmp->mmp_seq = cpu_to_le32(seq);
	160	mmp->mmp_time = cpu_to_le64(get_seconds());
	161	last_update_time = jiffies;
	162
5c359a47	163	retval = write_mmp_block(sb, bh);
c5e06d10 JL	164	/*
	165	* Don't spew too many error messages. Print one every
	166	* (s_mmp_update_interval * 60) seconds.
	167	*/
bdfc230f NA	168	if (retval) {
	169	if ((failed_writes % 60) == 0)
	170	ext4_error(sb, "Error writing to MMP block");
c5e06d10 JL	171	failed_writes++;
	172	}
	173
	174	if (!(le32_to_cpu(es->s_feature_incompat) &
	175	EXT4_FEATURE_INCOMPAT_MMP)) {
	176	ext4_warning(sb, "kmmpd being stopped since MMP feature"
	177	" has been disabled.");
	178	EXT4_SB(sb)->s_mmp_tsk = NULL;
	179	goto failed;
	180	}
	181
	182	if (sb->s_flags & MS_RDONLY) {
	183	ext4_warning(sb, "kmmpd being stopped since filesystem "
	184	"has been remounted as readonly.");
	185	EXT4_SB(sb)->s_mmp_tsk = NULL;
	186	goto failed;
	187	}
	188
	189	diff = jiffies - last_update_time;
	190	if (diff < mmp_update_interval * HZ)
	191	schedule_timeout_interruptible(mmp_update_interval *
	192	HZ - diff);
	193
	194	/*
	195	* We need to make sure that more than mmp_check_interval
	196	* seconds have not passed since writing. If that has happened
	197	* we need to check if the MMP block is as we left it.
	198	*/
	199	diff = jiffies - last_update_time;
	200	if (diff > mmp_check_interval * HZ) {
	201	struct buffer_head *bh_check = NULL;
	202	struct mmp_struct *mmp_check;
	203
	204	retval = read_mmp_block(sb, &bh_check, mmp_block);
	205	if (retval) {
	206	ext4_error(sb, "error reading MMP data: %d",
	207	retval);
	208
	209	EXT4_SB(sb)->s_mmp_tsk = NULL;
	210	goto failed;
	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	goto failed;
	223	}
	224	put_bh(bh_check);
	225	}
	226
	227	/*
	228	* Adjust the mmp_check_interval depending on how much time
	229	* it took for the MMP block to be written.
	230	*/
	231	mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
	232	EXT4_MMP_MAX_CHECK_INTERVAL),
	233	EXT4_MMP_MIN_CHECK_INTERVAL);
	234	mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
235	}
236
237	/*
238	* Unmount seems to be clean.
239	*/
240	mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
241	mmp->mmp_time = cpu_to_le64(get_seconds());
242
5c359a47	243	retval = write_mmp_block(sb, bh);
c5e06d10 JL	244
	245	failed:
	246	kfree(data);
	247	brelse(bh);
	248	return retval;
	249	}
	250
	251	/*
	252	* Get a random new sequence number but make sure it is not greater than
	253	* EXT4_MMP_SEQ_MAX.
	254	*/
	255	static unsigned int mmp_new_seq(void)
	256	{
	257	u32 new_seq;
	258
	259	do {
dd1f723b	260	new_seq = prandom_u32();
c5e06d10 JL	261	} while (new_seq > EXT4_MMP_SEQ_MAX);
	262
	263	return new_seq;
	264	}
	265
	266	/*
	267	* Protect the filesystem from being mounted more than once.
	268	*/
	269	int ext4_multi_mount_protect(struct super_block *sb,
	270	ext4_fsblk_t mmp_block)
	271	{
	272	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	273	struct buffer_head *bh = NULL;
	274	struct mmp_struct *mmp = NULL;
	275	struct mmpd_data *mmpd_data;
	276	u32 seq;
	277	unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
	278	unsigned int wait_time = 0;
	279	int retval;
	280
	281	if (mmp_block < le32_to_cpu(es->s_first_data_block) \|\|
	282	mmp_block >= ext4_blocks_count(es)) {
	283	ext4_warning(sb, "Invalid MMP block in superblock");
	284	goto failed;
	285	}
	286
	287	retval = read_mmp_block(sb, &bh, mmp_block);
	288	if (retval)
	289	goto failed;
	290
	291	mmp = (struct mmp_struct *)(bh->b_data);
	292
	293	if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
	294	mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
	295
	296	/*
	297	* If check_interval in MMP block is larger, use that instead of
	298	* update_interval from the superblock.
	299	*/
85d21650 SN	300	if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
85d21650 SN	301	mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
c5e06d10 JL	302
	303	seq = le32_to_cpu(mmp->mmp_seq);
	304	if (seq == EXT4_MMP_SEQ_CLEAN)
	305	goto skip;
	306
	307	if (seq == EXT4_MMP_SEQ_FSCK) {
	308	dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
	309	goto failed;
	310	}
	311
	312	wait_time = min(mmp_check_interval * 2 + 1,
	313	mmp_check_interval + 60);
	314
	315	/* Print MMP interval if more than 20 secs. */
	316	if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
	317	ext4_warning(sb, "MMP interval %u higher than expected, please"
	318	" wait.\n", wait_time * 2);
	319
	320	if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
	321	ext4_warning(sb, "MMP startup interrupted, failing mount\n");
	322	goto failed;
	323	}
	324
	325	retval = read_mmp_block(sb, &bh, mmp_block);
	326	if (retval)
	327	goto failed;
	328	mmp = (struct mmp_struct *)(bh->b_data);
	329	if (seq != le32_to_cpu(mmp->mmp_seq)) {
	330	dump_mmp_msg(sb, mmp,
	331	"Device is already active on another node.");
	332	goto failed;
	333	}
	334
	335	skip:
	336	/*
	337	* write a new random sequence number.
	338	*/
f6f96fdb DW	339	seq = mmp_new_seq();
f6f96fdb DW	340	mmp->mmp_seq = cpu_to_le32(seq);
c5e06d10	341
5c359a47	342	retval = write_mmp_block(sb, bh);
c5e06d10 JL	343	if (retval)
	344	goto failed;
	345
	346	/*
	347	* wait for MMP interval and check mmp_seq.
	348	*/
	349	if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
	350	ext4_warning(sb, "MMP startup interrupted, failing mount\n");
	351	goto failed;
	352	}
	353
	354	retval = read_mmp_block(sb, &bh, mmp_block);
	355	if (retval)
	356	goto failed;
	357	mmp = (struct mmp_struct *)(bh->b_data);
	358	if (seq != le32_to_cpu(mmp->mmp_seq)) {
	359	dump_mmp_msg(sb, mmp,
	360	"Device is already active on another node.");
	361	goto failed;
	362	}
	363
	364	mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
	365	if (!mmpd_data) {
	366	ext4_warning(sb, "not enough memory for mmpd_data");
	367	goto failed;
	368	}
	369	mmpd_data->sb = sb;
	370	mmpd_data->bh = bh;
	371
	372	/*
	373	* Start a kernel thread to update the MMP block periodically.
	374	*/
	375	EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
	376	bdevname(bh->b_bdev,
	377	mmp->mmp_bdevname));
	378	if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
	379	EXT4_SB(sb)->s_mmp_tsk = NULL;
	380	kfree(mmpd_data);
	381	ext4_warning(sb, "Unable to create kmmpd thread for %s.",
	382	sb->s_id);
	383	goto failed;
	384	}
	385
	386	return 0;
	387
	388	failed:
	389	brelse(bh);
	390	return 1;
	391	}
	392
	393