ext4: add support for multiple mount protection (c5e06d10) · Commits · 戴 / test

fs/ext4/Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -6,7 +6,8 @@ obj-$(CONFIG_EXT4_FS) += ext4.o

		ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
		ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
		ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o
		ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
		mmp.o

		ext4-$(CONFIG_EXT4_FS_XATTR) += xattr.o xattr_user.o xattr_trusted.o
		ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o

fs/ext4/ext4.h

+74 −2

Original line number	Diff line number	Diff line
		@@ -1028,7 +1028,7 @@ struct ext4_super_block {
		__le16 s_want_extra_isize; /* New inodes should reserve # bytes */
		__le32 s_flags; /* Miscellaneous flags */
		__le16 s_raid_stride; /* RAID stride */
		__le16 s_mmp_interval; /* # seconds to wait in MMP checking */
		__le16 s_mmp_update_interval; /* # seconds to wait in MMP checking */
		__le64 s_mmp_block; /* Block for multi-mount protection */
		__le32 s_raid_stripe_width; /* blocks on all data disks (Nstride)/
		__u8 s_log_groups_per_flex; /* FLEX_BG group size */
		@@ -1204,6 +1204,9 @@ struct ext4_sb_info {
		struct ext4_li_request *s_li_request;
		/* Wait multiplier for lazy initialization thread */
		unsigned int s_li_wait_mult;

		/* Kernel thread for multiple mount protection */
		struct task_struct *s_mmp_tsk;
		};

		static inline struct ext4_sb_info EXT4_SB(struct super_block sb)
		@@ -1375,7 +1378,8 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
		EXT4_FEATURE_INCOMPAT_META_BG\| \
		EXT4_FEATURE_INCOMPAT_EXTENTS\| \
		EXT4_FEATURE_INCOMPAT_64BIT\| \
		EXT4_FEATURE_INCOMPAT_FLEX_BG)
		EXT4_FEATURE_INCOMPAT_FLEX_BG\| \
		EXT4_FEATURE_INCOMPAT_MMP)
		#define EXT4_FEATURE_RO_COMPAT_SUPP (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER\| \
		EXT4_FEATURE_RO_COMPAT_LARGE_FILE\| \
		EXT4_FEATURE_RO_COMPAT_GDT_CSUM\| \
		@@ -1626,6 +1630,67 @@ struct ext4_features {
		struct completion f_kobj_unregister;
		};

		/*
		* This structure will be used for multiple mount protection. It will be
		* written into the block number saved in the s_mmp_block field in the
		* superblock. Programs that check MMP should assume that if
		* SEQ_FSCK (or any unknown code above SEQ_MAX) is present then it is NOT safe
		* to use the filesystem, regardless of how old the timestamp is.
		*/
		#define EXT4_MMP_MAGIC 0x004D4D50U /* ASCII for MMP */
		#define EXT4_MMP_SEQ_CLEAN 0xFF4D4D50U /* mmp_seq value for clean unmount */
		#define EXT4_MMP_SEQ_FSCK 0xE24D4D50U /* mmp_seq value when being fscked */
		#define EXT4_MMP_SEQ_MAX 0xE24D4D4FU /* maximum valid mmp_seq value */

		struct mmp_struct {
		__le32 mmp_magic; /* Magic number for MMP */
		__le32 mmp_seq; /* Sequence no. updated periodically */

		/*
		* mmp_time, mmp_nodename & mmp_bdevname are only used for information
		* purposes and do not affect the correctness of the algorithm
		*/
		__le64 mmp_time; /* Time last updated */
		char mmp_nodename[64]; /* Node which last updated MMP block */
		char mmp_bdevname[32]; /* Bdev which last updated MMP block */

		/*
		* mmp_check_interval is used to verify if the MMP block has been
		* updated on the block device. The value is updated based on the
		* maximum time to write the MMP block during an update cycle.
		*/
		__le16 mmp_check_interval;

		__le16 mmp_pad1;
		__le32 mmp_pad2[227];
		};

		/* arguments passed to the mmp thread */
		struct mmpd_data {
		struct buffer_head bh; / bh from initial read_mmp_block() */
		struct super_block sb; / super block of the fs */
		};

		/*
		* Check interval multiplier
		* The MMP block is written every update interval and initially checked every
		* update interval x the multiplier (the value is then adapted based on the
		* write latency). The reason is that writes can be delayed under load and we
		* don't want readers to incorrectly assume that the filesystem is no longer
		* in use.
		*/
		#define EXT4_MMP_CHECK_MULT 2UL

		/*
		* Minimum interval for MMP checking in seconds.
		*/
		#define EXT4_MMP_MIN_CHECK_INTERVAL 5UL

		/*
		* Maximum interval for MMP checking in seconds.
		*/
		#define EXT4_MMP_MAX_CHECK_INTERVAL 300UL

		/*
		* Function prototypes
		*/
		@@ -1800,6 +1865,10 @@ extern void __ext4_warning(struct super_block , const char , unsigned int,
		__LINE__, ## message)
		extern void ext4_msg(struct super_block , const char , const char *, ...)
		__attribute__ ((format (printf, 3, 4)));
		extern void __dump_mmp_msg(struct super_block , struct mmp_struct mmp,
		const char , unsigned int, const char );
		#define dump_mmp_msg(sb, mmp, msg) __dump_mmp_msg(sb, mmp, __func__, \
		__LINE__, msg)
		extern void __ext4_grp_locked_error(const char *, unsigned int, \
		struct super_block *, ext4_group_t, \
		unsigned long, ext4_fsblk_t, \
		@@ -2104,6 +2173,9 @@ extern int ext4_bio_write_page(struct ext4_io_submit *io,
		int len,
		struct writeback_control *wbc);

		/* mmp.c */
		extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);

		/* BH_Uninit flag: blocks are allocated but uninitialized on disk */
		enum ext4_state_bits {
		BH_Uninit /* blocks are allocated but uninitialized on disk */

fs/ext4/mmp.c

0 → 100644

+351 −0

Original line number	Diff line number	Diff line
		#include <linux/fs.h>
		#include <linux/random.h>
		#include <linux/buffer_head.h>
		#include <linux/utsname.h>
		#include <linux/kthread.h>

		#include "ext4.h"

		/*
		* Write the MMP block using WRITE_SYNC to try to get the block on-disk
		* faster.
		*/
		static int write_mmp_block(struct buffer_head *bh)
		{
		mark_buffer_dirty(bh);
		lock_buffer(bh);
		bh->b_end_io = end_buffer_write_sync;
		get_bh(bh);
		submit_bh(WRITE_SYNC, bh);
		wait_on_buffer(bh);
		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) {
		get_bh(*bh);
		lock_buffer(*bh);
		(*bh)->b_end_io = end_buffer_read_sync;
		submit_bh(READ_SYNC, *bh);
		wait_on_buffer(*bh);
		if (!buffer_uptodate(*bh)) {
		brelse(*bh);
		*bh = NULL;
		}
		}
		if (!*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)
		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()->sysname,
		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(bh);
		/*
		* Don't spew too many error messages. Print one every
		* (s_mmp_update_interval * 60) seconds.
		*/
		if (retval && (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(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 (mmp->mmp_check_interval > mmp_check_interval)
		mmp_check_interval = 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.
		*/
		mmp->mmp_seq = seq = cpu_to_le32(mmp_new_seq());

		retval = write_mmp_block(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;
		}

fs/ext4/super.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -822,6 +822,8 @@ static void ext4_put_super(struct super_block *sb)
		invalidate_bdev(sbi->journal_bdev);
		ext4_blkdev_remove(sbi);
		}
		if (sbi->s_mmp_tsk)
		kthread_stop(sbi->s_mmp_tsk);
		sb->s_fs_info = NULL;
		/*
		* Now that we are completely done shutting down the
		@@ -3486,6 +3488,11 @@ static int ext4_fill_super(struct super_block sb, void data, int silent)
		EXT4_HAS_INCOMPAT_FEATURE(sb,
		EXT4_FEATURE_INCOMPAT_RECOVER));

		if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_MMP) &&
		!(sb->s_flags & MS_RDONLY))
		if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
		goto failed_mount3;

		/*
		* The first inode we look at is the journal inode. Don't try
		* root first: it may be modified in the journal!
		@@ -3733,6 +3740,8 @@ failed_mount3:
		percpu_counter_destroy(&sbi->s_freeinodes_counter);
		percpu_counter_destroy(&sbi->s_dirs_counter);
		percpu_counter_destroy(&sbi->s_dirtyblocks_counter);
		if (sbi->s_mmp_tsk)
		kthread_stop(sbi->s_mmp_tsk);
		failed_mount2:
		for (i = 0; i < db_count; i++)
		brelse(sbi->s_group_desc[i]);
		@@ -4268,7 +4277,7 @@ static int ext4_remount(struct super_block sb, int flags, char *data)
		int enable_quota = 0;
		ext4_group_t g;
		unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
		int err;
		int err = 0;
		#ifdef CONFIG_QUOTA
		int i;
		#endif
		@@ -4394,6 +4403,13 @@ static int ext4_remount(struct super_block sb, int flags, char *data)
		goto restore_opts;
		if (!ext4_setup_super(sb, es, 0))
		sb->s_flags &= ~MS_RDONLY;
		if (EXT4_HAS_INCOMPAT_FEATURE(sb,
		EXT4_FEATURE_INCOMPAT_MMP))
		if (ext4_multi_mount_protect(sb,
		le64_to_cpu(es->s_mmp_block))) {
		err = -EROFS;
		goto restore_opts;
		}
		enable_quota = 1;
		}
		}

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