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![Li Dongyang](/assets/img/avatar_default.png)
Marking mmp bh dirty before writing it will make writeback pick up mmp block later and submit a write, we don't want the duplicate write as kmmpd thread should have full control of reading and writing the mmp block. Another reason is we will also have random I/O error on the writeback request when blk integrity is enabled, because kmmpd could modify the content of the mmp block(e.g. setting new seq and time) while the mmp block is under I/O requested by writeback. Signed-off-by: Li Dongyang <dongyangli@ddn.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Andreas Dilger <adilger@dilger.ca> Cc: stable@vger.kernel.org
396 lines
9.9 KiB
C
396 lines
9.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/fs.h>
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#include <linux/random.h>
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#include <linux/buffer_head.h>
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#include <linux/utsname.h>
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#include <linux/kthread.h>
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#include "ext4.h"
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/* Checksumming functions */
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static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
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{
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struct ext4_sb_info *sbi = EXT4_SB(sb);
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int offset = offsetof(struct mmp_struct, mmp_checksum);
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__u32 csum;
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csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
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return cpu_to_le32(csum);
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}
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static int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
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{
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if (!ext4_has_metadata_csum(sb))
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return 1;
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return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
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}
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static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
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{
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if (!ext4_has_metadata_csum(sb))
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return;
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mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
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}
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/*
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* Write the MMP block using REQ_SYNC to try to get the block on-disk
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* faster.
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*/
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static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
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{
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struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
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/*
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* We protect against freezing so that we don't create dirty buffers
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* on frozen filesystem.
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*/
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sb_start_write(sb);
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ext4_mmp_csum_set(sb, mmp);
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lock_buffer(bh);
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bh->b_end_io = end_buffer_write_sync;
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get_bh(bh);
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submit_bh(REQ_OP_WRITE, REQ_SYNC | REQ_META | REQ_PRIO, bh);
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wait_on_buffer(bh);
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sb_end_write(sb);
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if (unlikely(!buffer_uptodate(bh)))
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return 1;
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return 0;
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}
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/*
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* Read the MMP block. It _must_ be read from disk and hence we clear the
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* uptodate flag on the buffer.
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*/
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static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
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ext4_fsblk_t mmp_block)
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{
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struct mmp_struct *mmp;
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int ret;
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if (*bh)
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clear_buffer_uptodate(*bh);
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/* This would be sb_bread(sb, mmp_block), except we need to be sure
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* that the MD RAID device cache has been bypassed, and that the read
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* is not blocked in the elevator. */
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if (!*bh) {
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*bh = sb_getblk(sb, mmp_block);
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if (!*bh) {
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ret = -ENOMEM;
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goto warn_exit;
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}
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}
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get_bh(*bh);
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lock_buffer(*bh);
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(*bh)->b_end_io = end_buffer_read_sync;
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submit_bh(REQ_OP_READ, REQ_META | REQ_PRIO, *bh);
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wait_on_buffer(*bh);
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if (!buffer_uptodate(*bh)) {
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ret = -EIO;
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goto warn_exit;
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}
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mmp = (struct mmp_struct *)((*bh)->b_data);
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if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC) {
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ret = -EFSCORRUPTED;
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goto warn_exit;
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}
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if (!ext4_mmp_csum_verify(sb, mmp)) {
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ret = -EFSBADCRC;
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goto warn_exit;
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}
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return 0;
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warn_exit:
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brelse(*bh);
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*bh = NULL;
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ext4_warning(sb, "Error %d while reading MMP block %llu",
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ret, mmp_block);
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return ret;
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}
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/*
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* Dump as much information as possible to help the admin.
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*/
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void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
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const char *function, unsigned int line, const char *msg)
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{
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__ext4_warning(sb, function, line, "%s", msg);
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__ext4_warning(sb, function, line,
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"MMP failure info: last update time: %llu, last update "
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"node: %s, last update device: %s",
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(long long unsigned int) le64_to_cpu(mmp->mmp_time),
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mmp->mmp_nodename, mmp->mmp_bdevname);
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}
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/*
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* kmmpd will update the MMP sequence every s_mmp_update_interval seconds
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*/
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static int kmmpd(void *data)
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{
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struct super_block *sb = ((struct mmpd_data *) data)->sb;
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struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
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struct ext4_super_block *es = EXT4_SB(sb)->s_es;
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struct mmp_struct *mmp;
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ext4_fsblk_t mmp_block;
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u32 seq = 0;
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unsigned long failed_writes = 0;
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int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
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unsigned mmp_check_interval;
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unsigned long last_update_time;
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unsigned long diff;
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int retval;
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mmp_block = le64_to_cpu(es->s_mmp_block);
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mmp = (struct mmp_struct *)(bh->b_data);
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mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
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/*
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* Start with the higher mmp_check_interval and reduce it if
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* the MMP block is being updated on time.
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*/
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mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
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EXT4_MMP_MIN_CHECK_INTERVAL);
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mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
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bdevname(bh->b_bdev, mmp->mmp_bdevname);
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memcpy(mmp->mmp_nodename, init_utsname()->nodename,
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sizeof(mmp->mmp_nodename));
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while (!kthread_should_stop()) {
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if (++seq > EXT4_MMP_SEQ_MAX)
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seq = 1;
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mmp->mmp_seq = cpu_to_le32(seq);
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mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
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last_update_time = jiffies;
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retval = write_mmp_block(sb, bh);
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/*
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* Don't spew too many error messages. Print one every
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* (s_mmp_update_interval * 60) seconds.
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*/
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if (retval) {
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if ((failed_writes % 60) == 0)
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ext4_error(sb, "Error writing to MMP block");
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failed_writes++;
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}
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if (!(le32_to_cpu(es->s_feature_incompat) &
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EXT4_FEATURE_INCOMPAT_MMP)) {
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ext4_warning(sb, "kmmpd being stopped since MMP feature"
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" has been disabled.");
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goto exit_thread;
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}
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if (sb_rdonly(sb))
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break;
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diff = jiffies - last_update_time;
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if (diff < mmp_update_interval * HZ)
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schedule_timeout_interruptible(mmp_update_interval *
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HZ - diff);
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/*
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* We need to make sure that more than mmp_check_interval
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* seconds have not passed since writing. If that has happened
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* we need to check if the MMP block is as we left it.
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*/
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diff = jiffies - last_update_time;
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if (diff > mmp_check_interval * HZ) {
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struct buffer_head *bh_check = NULL;
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struct mmp_struct *mmp_check;
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retval = read_mmp_block(sb, &bh_check, mmp_block);
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if (retval) {
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ext4_error(sb, "error reading MMP data: %d",
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retval);
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goto exit_thread;
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}
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mmp_check = (struct mmp_struct *)(bh_check->b_data);
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if (mmp->mmp_seq != mmp_check->mmp_seq ||
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memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
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sizeof(mmp->mmp_nodename))) {
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dump_mmp_msg(sb, mmp_check,
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"Error while updating MMP info. "
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"The filesystem seems to have been"
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" multiply mounted.");
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ext4_error(sb, "abort");
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put_bh(bh_check);
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retval = -EBUSY;
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goto exit_thread;
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}
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put_bh(bh_check);
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}
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/*
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* Adjust the mmp_check_interval depending on how much time
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* it took for the MMP block to be written.
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*/
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mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
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EXT4_MMP_MAX_CHECK_INTERVAL),
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EXT4_MMP_MIN_CHECK_INTERVAL);
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mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
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}
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/*
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* Unmount seems to be clean.
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*/
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mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
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mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
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retval = write_mmp_block(sb, bh);
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exit_thread:
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EXT4_SB(sb)->s_mmp_tsk = NULL;
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kfree(data);
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brelse(bh);
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return retval;
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}
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/*
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* Get a random new sequence number but make sure it is not greater than
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* EXT4_MMP_SEQ_MAX.
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*/
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static unsigned int mmp_new_seq(void)
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{
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u32 new_seq;
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do {
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new_seq = prandom_u32();
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} while (new_seq > EXT4_MMP_SEQ_MAX);
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return new_seq;
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}
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/*
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* Protect the filesystem from being mounted more than once.
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*/
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int ext4_multi_mount_protect(struct super_block *sb,
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ext4_fsblk_t mmp_block)
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{
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struct ext4_super_block *es = EXT4_SB(sb)->s_es;
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struct buffer_head *bh = NULL;
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struct mmp_struct *mmp = NULL;
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struct mmpd_data *mmpd_data;
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u32 seq;
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unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
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unsigned int wait_time = 0;
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int retval;
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if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
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mmp_block >= ext4_blocks_count(es)) {
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ext4_warning(sb, "Invalid MMP block in superblock");
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goto failed;
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}
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retval = read_mmp_block(sb, &bh, mmp_block);
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if (retval)
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goto failed;
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mmp = (struct mmp_struct *)(bh->b_data);
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if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
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mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
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/*
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* If check_interval in MMP block is larger, use that instead of
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* update_interval from the superblock.
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*/
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if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
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mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
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seq = le32_to_cpu(mmp->mmp_seq);
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if (seq == EXT4_MMP_SEQ_CLEAN)
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goto skip;
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if (seq == EXT4_MMP_SEQ_FSCK) {
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dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
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goto failed;
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}
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wait_time = min(mmp_check_interval * 2 + 1,
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mmp_check_interval + 60);
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/* Print MMP interval if more than 20 secs. */
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if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
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ext4_warning(sb, "MMP interval %u higher than expected, please"
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" wait.\n", wait_time * 2);
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if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
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ext4_warning(sb, "MMP startup interrupted, failing mount\n");
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goto failed;
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}
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retval = read_mmp_block(sb, &bh, mmp_block);
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if (retval)
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goto failed;
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mmp = (struct mmp_struct *)(bh->b_data);
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if (seq != le32_to_cpu(mmp->mmp_seq)) {
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dump_mmp_msg(sb, mmp,
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"Device is already active on another node.");
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goto failed;
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}
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skip:
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/*
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* write a new random sequence number.
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*/
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seq = mmp_new_seq();
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mmp->mmp_seq = cpu_to_le32(seq);
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retval = write_mmp_block(sb, bh);
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if (retval)
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goto failed;
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/*
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* wait for MMP interval and check mmp_seq.
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*/
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if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
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ext4_warning(sb, "MMP startup interrupted, failing mount");
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goto failed;
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}
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retval = read_mmp_block(sb, &bh, mmp_block);
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if (retval)
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goto failed;
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mmp = (struct mmp_struct *)(bh->b_data);
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if (seq != le32_to_cpu(mmp->mmp_seq)) {
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dump_mmp_msg(sb, mmp,
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"Device is already active on another node.");
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goto failed;
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}
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mmpd_data = kmalloc(sizeof(*mmpd_data), GFP_KERNEL);
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if (!mmpd_data) {
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ext4_warning(sb, "not enough memory for mmpd_data");
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goto failed;
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}
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mmpd_data->sb = sb;
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mmpd_data->bh = bh;
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/*
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* Start a kernel thread to update the MMP block periodically.
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*/
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EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
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bdevname(bh->b_bdev,
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mmp->mmp_bdevname));
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if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
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EXT4_SB(sb)->s_mmp_tsk = NULL;
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kfree(mmpd_data);
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ext4_warning(sb, "Unable to create kmmpd thread for %s.",
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sb->s_id);
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goto failed;
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}
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return 0;
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failed:
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brelse(bh);
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return 1;
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}
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