summaryrefslogtreecommitdiff
path: root/fs/ext4/mmp.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/ext4/mmp.c')
-rw-r--r--fs/ext4/mmp.c353
1 files changed, 353 insertions, 0 deletions
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
new file mode 100644
index 00000000..ed6548d8
--- /dev/null
+++ b/fs/ext4/mmp.c
@@ -0,0 +1,353 @@
+#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()->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(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(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(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;
+}
+
+
generated by cgit (git 2.34.1) at 2024-12-23 08:13:01 +0000