[GitHub/mt8127/android_kernel_alcatel_ttab.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);
}

int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
{
	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
		return 1;

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

void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
{
	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
		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 {
		get_random_bytes(&new_seq, sizeof(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
	21	int 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
	30	void 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
c5e06d10 JL	39	/*
	40	* Write the MMP block using WRITE_SYNC to try to get the block on-disk
	41	* faster.
	42	*/
5c359a47	43	static int write_mmp_block(struct super_block sb, struct buffer_head bh)
c5e06d10	44	{
5c359a47 DW	45	struct mmp_struct mmp = (struct mmp_struct )(bh->b_data);
5c359a47 DW	46
8e8ad8a5 JK	47	/*
	48	* We protect against freezing so that we don't create dirty buffers
	49	* on frozen filesystem.
	50	*/
	51	sb_start_write(sb);
5c359a47	52	ext4_mmp_csum_set(sb, mmp);
c5e06d10 JL	53	mark_buffer_dirty(bh);
	54	lock_buffer(bh);
	55	bh->b_end_io = end_buffer_write_sync;
	56	get_bh(bh);
9f203507	57	submit_bh(WRITE_SYNC \| REQ_META \| REQ_PRIO, bh);
c5e06d10	58	wait_on_buffer(bh);
8e8ad8a5	59	sb_end_write(sb);
c5e06d10 JL	60	if (unlikely(!buffer_uptodate(bh)))
	61	return 1;
	62
	63	return 0;
	64	}
	65
	66	/*
	67	* Read the MMP block. It _must_ be read from disk and hence we clear the
	68	* uptodate flag on the buffer.
	69	*/
	70	static int read_mmp_block(struct super_block sb, struct buffer_head *bh,
	71	ext4_fsblk_t mmp_block)
	72	{
	73	struct mmp_struct *mmp;
	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);
860d21e2 TT	83	if (!*bh)
860d21e2 TT	84	return -ENOMEM;
c5e06d10 JL	85	if (*bh) {
	86	get_bh(*bh);
	87	lock_buffer(*bh);
	88	(*bh)->b_end_io = end_buffer_read_sync;
9f203507	89	submit_bh(READ_SYNC \| REQ_META \| REQ_PRIO, *bh);
c5e06d10 JL	90	wait_on_buffer(*bh);
	91	if (!buffer_uptodate(*bh)) {
	92	brelse(*bh);
	93	*bh = NULL;
	94	}
	95	}
aebf0243	96	if (unlikely(!*bh)) {
c5e06d10 JL	97	ext4_warning(sb, "Error while reading MMP block %llu",
	98	mmp_block);
	99	return -EIO;
	100	}
	101
	102	mmp = (struct mmp_struct )((bh)->b_data);
5c359a47 DW	103	if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC \|\|
5c359a47 DW	104	!ext4_mmp_csum_verify(sb, mmp))
c5e06d10 JL	105	return -EINVAL;
	106
	107	return 0;
	108	}
	109
	110	/*
	111	* Dump as much information as possible to help the admin.
	112	*/
	113	void __dump_mmp_msg(struct super_block sb, struct mmp_struct mmp,
	114	const char function, unsigned int line, const char msg)
	115	{
	116	__ext4_warning(sb, function, line, msg);
	117	__ext4_warning(sb, function, line,
	118	"MMP failure info: last update time: %llu, last update "
	119	"node: %s, last update device: %s\n",
	120	(long long unsigned int) le64_to_cpu(mmp->mmp_time),
	121	mmp->mmp_nodename, mmp->mmp_bdevname);
	122	}
	123
	124	/*
	125	* kmmpd will update the MMP sequence every s_mmp_update_interval seconds
	126	*/
	127	static int kmmpd(void *data)
	128	{
	129	struct super_block sb = ((struct mmpd_data ) data)->sb;
	130	struct buffer_head bh = ((struct mmpd_data ) data)->bh;
	131	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	132	struct mmp_struct *mmp;
	133	ext4_fsblk_t mmp_block;
	134	u32 seq = 0;
	135	unsigned long failed_writes = 0;
	136	int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
	137	unsigned mmp_check_interval;
	138	unsigned long last_update_time;
	139	unsigned long diff;
	140	int retval;
	141
	142	mmp_block = le64_to_cpu(es->s_mmp_block);
	143	mmp = (struct mmp_struct *)(bh->b_data);
	144	mmp->mmp_time = cpu_to_le64(get_seconds());
	145	/*
	146	* Start with the higher mmp_check_interval and reduce it if
	147	* the MMP block is being updated on time.
	148	*/
	149	mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
	150	EXT4_MMP_MIN_CHECK_INTERVAL);
	151	mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
	152	bdevname(bh->b_bdev, mmp->mmp_bdevname);
	153
215fc6af	154	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
c5e06d10 JL	155	sizeof(mmp->mmp_nodename));
	156
	157	while (!kthread_should_stop()) {
	158	if (++seq > EXT4_MMP_SEQ_MAX)
	159	seq = 1;
	160
	161	mmp->mmp_seq = cpu_to_le32(seq);
	162	mmp->mmp_time = cpu_to_le64(get_seconds());
	163	last_update_time = jiffies;
	164
5c359a47	165	retval = write_mmp_block(sb, bh);
c5e06d10 JL	166	/*
	167	* Don't spew too many error messages. Print one every
	168	* (s_mmp_update_interval * 60) seconds.
	169	*/
bdfc230f NA	170	if (retval) {
	171	if ((failed_writes % 60) == 0)
	172	ext4_error(sb, "Error writing to MMP block");
c5e06d10 JL	173	failed_writes++;
	174	}
	175
	176	if (!(le32_to_cpu(es->s_feature_incompat) &
	177	EXT4_FEATURE_INCOMPAT_MMP)) {
	178	ext4_warning(sb, "kmmpd being stopped since MMP feature"
	179	" has been disabled.");
	180	EXT4_SB(sb)->s_mmp_tsk = NULL;
	181	goto failed;
	182	}
	183
	184	if (sb->s_flags & MS_RDONLY) {
	185	ext4_warning(sb, "kmmpd being stopped since filesystem "
	186	"has been remounted as readonly.");
	187	EXT4_SB(sb)->s_mmp_tsk = NULL;
	188	goto failed;
	189	}
	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
	211	EXT4_SB(sb)->s_mmp_tsk = NULL;
	212	goto failed;
	213	}
	214
	215	mmp_check = (struct mmp_struct *)(bh_check->b_data);
	216	if (mmp->mmp_seq != mmp_check->mmp_seq \|\|
	217	memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
	218	sizeof(mmp->mmp_nodename))) {
	219	dump_mmp_msg(sb, mmp_check,
	220	"Error while updating MMP info. "
	221	"The filesystem seems to have been"
	222	" multiply mounted.");
	223	ext4_error(sb, "abort");
	224	goto failed;
	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(get_seconds());
244
5c359a47	245	retval = write_mmp_block(sb, bh);
c5e06d10 JL	246
	247	failed:
	248	kfree(data);
	249	brelse(bh);
	250	return retval;
	251	}
	252
	253	/*
	254	* Get a random new sequence number but make sure it is not greater than
	255	* EXT4_MMP_SEQ_MAX.
	256	*/
	257	static unsigned int mmp_new_seq(void)
	258	{
	259	u32 new_seq;
	260
	261	do {
	262	get_random_bytes(&new_seq, sizeof(u32));
	263	} while (new_seq > EXT4_MMP_SEQ_MAX);
	264
	265	return new_seq;
	266	}
	267
	268	/*
	269	* Protect the filesystem from being mounted more than once.
	270	*/
	271	int ext4_multi_mount_protect(struct super_block *sb,
	272	ext4_fsblk_t mmp_block)
	273	{
	274	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	275	struct buffer_head *bh = NULL;
	276	struct mmp_struct *mmp = NULL;
	277	struct mmpd_data *mmpd_data;
	278	u32 seq;
	279	unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
	280	unsigned int wait_time = 0;
	281	int retval;
	282
	283	if (mmp_block < le32_to_cpu(es->s_first_data_block) \|\|
	284	mmp_block >= ext4_blocks_count(es)) {
	285	ext4_warning(sb, "Invalid MMP block in superblock");
	286	goto failed;
	287	}
	288
	289	retval = read_mmp_block(sb, &bh, mmp_block);
	290	if (retval)
	291	goto failed;
	292
	293	mmp = (struct mmp_struct *)(bh->b_data);
	294
	295	if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
	296	mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
	297
	298	/*
	299	* If check_interval in MMP block is larger, use that instead of
	300	* update_interval from the superblock.
	301	*/
85d21650 SN	302	if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
85d21650 SN	303	mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
c5e06d10 JL	304
	305	seq = le32_to_cpu(mmp->mmp_seq);
	306	if (seq == EXT4_MMP_SEQ_CLEAN)
	307	goto skip;
	308
	309	if (seq == EXT4_MMP_SEQ_FSCK) {
	310	dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
	311	goto failed;
	312	}
	313
	314	wait_time = min(mmp_check_interval * 2 + 1,
	315	mmp_check_interval + 60);
	316
	317	/* Print MMP interval if more than 20 secs. */
	318	if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
	319	ext4_warning(sb, "MMP interval %u higher than expected, please"
	320	" wait.\n", wait_time * 2);
	321
	322	if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
	323	ext4_warning(sb, "MMP startup interrupted, failing mount\n");
	324	goto failed;
	325	}
	326
	327	retval = read_mmp_block(sb, &bh, mmp_block);
	328	if (retval)
	329	goto failed;
	330	mmp = (struct mmp_struct *)(bh->b_data);
	331	if (seq != le32_to_cpu(mmp->mmp_seq)) {
	332	dump_mmp_msg(sb, mmp,
	333	"Device is already active on another node.");
	334	goto failed;
	335	}
	336
	337	skip:
	338	/*
	339	* write a new random sequence number.
	340	*/
f6f96fdb DW	341	seq = mmp_new_seq();
f6f96fdb DW	342	mmp->mmp_seq = cpu_to_le32(seq);
c5e06d10	343
5c359a47	344	retval = write_mmp_block(sb, bh);
c5e06d10 JL	345	if (retval)
	346	goto failed;
	347
	348	/*
	349	* wait for MMP interval and check mmp_seq.
	350	*/
	351	if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
	352	ext4_warning(sb, "MMP startup interrupted, failing mount\n");
	353	goto failed;
	354	}
	355
	356	retval = read_mmp_block(sb, &bh, mmp_block);
	357	if (retval)
	358	goto failed;
	359	mmp = (struct mmp_struct *)(bh->b_data);
	360	if (seq != le32_to_cpu(mmp->mmp_seq)) {
	361	dump_mmp_msg(sb, mmp,
	362	"Device is already active on another node.");
	363	goto failed;
	364	}
	365
	366	mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
	367	if (!mmpd_data) {
	368	ext4_warning(sb, "not enough memory for mmpd_data");
	369	goto failed;
	370	}
	371	mmpd_data->sb = sb;
	372	mmpd_data->bh = bh;
	373
	374	/*
	375	* Start a kernel thread to update the MMP block periodically.
	376	*/
	377	EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
	378	bdevname(bh->b_bdev,
	379	mmp->mmp_bdevname));
	380	if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
	381	EXT4_SB(sb)->s_mmp_tsk = NULL;
	382	kfree(mmpd_data);
	383	ext4_warning(sb, "Unable to create kmmpd thread for %s.",
	384	sb->s_id);
	385	goto failed;
	386	}
	387
	388	return 0;
	389
	390	failed:
	391	brelse(bh);
	392	return 1;
	393	}
	394
	395