---

yaml
---
r: 251753
b: refs/heads/master
c: c5e06d1
h: refs/heads/master
i:
  251751: a2c39e5
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d02a9391f79cab65cde74cd9e8ccd2290a565229
+refs/heads/master: c5e06d101aaf72f1f2192a661414459775e9bd74

trunk/fs/ext4/Makefile

@@ -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

trunk/fs/ext4/ext4.h

@@ -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 (N*stride)*/
 	__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 */