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-rw-r--r--fs/ext4/mmp.c408
1 files changed, 408 insertions, 0 deletions
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
new file mode 100644
index 0000000000..bd946d0c71
--- /dev/null
+++ b/fs/ext4/mmp.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0
+#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 REQ_SYNC to try to get the block on-disk
+ * faster.
+ */
+static int write_mmp_block_thawed(struct super_block *sb,
+ struct buffer_head *bh)
+{
+ struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
+
+ ext4_mmp_csum_set(sb, mmp);
+ lock_buffer(bh);
+ bh->b_end_io = end_buffer_write_sync;
+ get_bh(bh);
+ submit_bh(REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO, bh);
+ wait_on_buffer(bh);
+ if (unlikely(!buffer_uptodate(bh)))
+ return -EIO;
+ return 0;
+}
+
+static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
+{
+ int err;
+
+ /*
+ * We protect against freezing so that we don't create dirty buffers
+ * on frozen filesystem.
+ */
+ sb_start_write(sb);
+ err = write_mmp_block_thawed(sb, bh);
+ sb_end_write(sb);
+ return err;
+}
+
+/*
+ * 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;
+ int ret;
+
+ 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) {
+ ret = -ENOMEM;
+ goto warn_exit;
+ }
+ }
+
+ lock_buffer(*bh);
+ ret = ext4_read_bh(*bh, REQ_META | REQ_PRIO, NULL);
+ if (ret)
+ goto warn_exit;
+
+ mmp = (struct mmp_struct *)((*bh)->b_data);
+ if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC) {
+ ret = -EFSCORRUPTED;
+ goto warn_exit;
+ }
+ if (!ext4_mmp_csum_verify(sb, mmp)) {
+ ret = -EFSBADCRC;
+ goto warn_exit;
+ }
+ return 0;
+warn_exit:
+ brelse(*bh);
+ *bh = NULL;
+ ext4_warning(sb, "Error %d while reading MMP block %llu",
+ ret, mmp_block);
+ return ret;
+}
+
+/*
+ * 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, "%s", msg);
+ __ext4_warning(sb, function, line,
+ "MMP failure info: last update time: %llu, last update node: %.*s, last update device: %.*s",
+ (unsigned long long)le64_to_cpu(mmp->mmp_time),
+ (int)sizeof(mmp->mmp_nodename), mmp->mmp_nodename,
+ (int)sizeof(mmp->mmp_bdevname), mmp->mmp_bdevname);
+}
+
+/*
+ * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
+ */
+static int kmmpd(void *data)
+{
+ struct super_block *sb = data;
+ struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+ struct buffer_head *bh = EXT4_SB(sb)->s_mmp_bh;
+ 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 = 0;
+
+ mmp_block = le64_to_cpu(es->s_mmp_block);
+ mmp = (struct mmp_struct *)(bh->b_data);
+ mmp->mmp_time = cpu_to_le64(ktime_get_real_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);
+
+ memcpy(mmp->mmp_nodename, init_utsname()->nodename,
+ sizeof(mmp->mmp_nodename));
+
+ while (!kthread_should_stop() && !ext4_forced_shutdown(sb)) {
+ if (!ext4_has_feature_mmp(sb)) {
+ ext4_warning(sb, "kmmpd being stopped since MMP feature"
+ " has been disabled.");
+ goto wait_to_exit;
+ }
+ if (++seq > EXT4_MMP_SEQ_MAX)
+ seq = 1;
+
+ mmp->mmp_seq = cpu_to_le32(seq);
+ mmp->mmp_time = cpu_to_le64(ktime_get_real_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_err(sb, -retval,
+ "Error writing to MMP block");
+ }
+ failed_writes++;
+ }
+
+ 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_err(sb, -retval,
+ "error reading MMP data: %d",
+ retval);
+ goto wait_to_exit;
+ }
+
+ 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_err(sb, EBUSY, "abort");
+ put_bh(bh_check);
+ retval = -EBUSY;
+ goto wait_to_exit;
+ }
+ 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(ktime_get_real_seconds());
+
+ retval = write_mmp_block(sb, bh);
+
+wait_to_exit:
+ while (!kthread_should_stop()) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (!kthread_should_stop())
+ schedule();
+ }
+ set_current_state(TASK_RUNNING);
+ return retval;
+}
+
+void ext4_stop_mmpd(struct ext4_sb_info *sbi)
+{
+ if (sbi->s_mmp_tsk) {
+ kthread_stop(sbi->s_mmp_tsk);
+ brelse(sbi->s_mmp_bh);
+ sbi->s_mmp_tsk = NULL;
+ }
+}
+
+/*
+ * 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)
+{
+ return get_random_u32_below(EXT4_MMP_SEQ_MAX + 1);
+}
+
+/*
+ * 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;
+ 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");
+ retval = -EINVAL;
+ 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");
+ retval = -EBUSY;
+ 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");
+ retval = -ETIMEDOUT;
+ 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.");
+ retval = -EBUSY;
+ goto failed;
+ }
+
+skip:
+ /*
+ * write a new random sequence number.
+ */
+ seq = mmp_new_seq();
+ mmp->mmp_seq = cpu_to_le32(seq);
+
+ /*
+ * On mount / remount we are protected against fs freezing (by s_umount
+ * semaphore) and grabbing freeze protection upsets lockdep
+ */
+ retval = write_mmp_block_thawed(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");
+ retval = -ETIMEDOUT;
+ 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.");
+ retval = -EBUSY;
+ goto failed;
+ }
+
+ EXT4_SB(sb)->s_mmp_bh = bh;
+
+ BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
+ snprintf(mmp->mmp_bdevname, sizeof(mmp->mmp_bdevname),
+ "%pg", bh->b_bdev);
+
+ /*
+ * Start a kernel thread to update the MMP block periodically.
+ */
+ EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s",
+ (int)sizeof(mmp->mmp_bdevname),
+ mmp->mmp_bdevname);
+ if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
+ EXT4_SB(sb)->s_mmp_tsk = NULL;
+ ext4_warning(sb, "Unable to create kmmpd thread for %s.",
+ sb->s_id);
+ retval = -ENOMEM;
+ goto failed;
+ }
+
+ return 0;
+
+failed:
+ brelse(bh);
+ return retval;
+}
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