LCOV - code coverage report
Current view: top level - fs/ext4 - mmp.c (source / functions) Hit Total Coverage
Test: gcov_data_raspi2_real_modules_combined.info Lines: 0 150 0.0 %
Date: 2020-09-30 20:25:40 Functions: 0 7 0.0 %
Branches: 0 78 0.0 %

           Branch data     Line data    Source code
       1                 :            : // SPDX-License-Identifier: GPL-2.0
       2                 :            : #include <linux/fs.h>
       3                 :            : #include <linux/random.h>
       4                 :            : #include <linux/buffer_head.h>
       5                 :            : #include <linux/utsname.h>
       6                 :            : #include <linux/kthread.h>
       7                 :            : 
       8                 :            : #include "ext4.h"
       9                 :            : 
      10                 :            : /* Checksumming functions */
      11                 :            : static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
      12                 :            : {
      13                 :            :         struct ext4_sb_info *sbi = EXT4_SB(sb);
      14                 :            :         int offset = offsetof(struct mmp_struct, mmp_checksum);
      15                 :            :         __u32 csum;
      16                 :            : 
      17                 :          0 :         csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
      18                 :            : 
      19                 :            :         return cpu_to_le32(csum);
      20                 :            : }
      21                 :            : 
      22                 :          0 : static int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
      23                 :            : {
      24         [ #  # ]:          0 :         if (!ext4_has_metadata_csum(sb))
      25                 :            :                 return 1;
      26                 :            : 
      27                 :          0 :         return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
      28                 :            : }
      29                 :            : 
      30                 :          0 : static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
      31                 :            : {
      32         [ #  # ]:          0 :         if (!ext4_has_metadata_csum(sb))
      33                 :          0 :                 return;
      34                 :            : 
      35                 :          0 :         mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
      36                 :            : }
      37                 :            : 
      38                 :            : /*
      39                 :            :  * Write the MMP block using REQ_SYNC to try to get the block on-disk
      40                 :            :  * faster.
      41                 :            :  */
      42                 :          0 : static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
      43                 :            : {
      44                 :          0 :         struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
      45                 :            : 
      46                 :            :         /*
      47                 :            :          * We protect against freezing so that we don't create dirty buffers
      48                 :            :          * on frozen filesystem.
      49                 :            :          */
      50                 :            :         sb_start_write(sb);
      51                 :          0 :         ext4_mmp_csum_set(sb, mmp);
      52                 :          0 :         lock_buffer(bh);
      53                 :          0 :         bh->b_end_io = end_buffer_write_sync;
      54                 :            :         get_bh(bh);
      55                 :          0 :         submit_bh(REQ_OP_WRITE, REQ_SYNC | REQ_META | REQ_PRIO, bh);
      56                 :          0 :         wait_on_buffer(bh);
      57                 :            :         sb_end_write(sb);
      58         [ #  # ]:          0 :         if (unlikely(!buffer_uptodate(bh)))
      59                 :            :                 return 1;
      60                 :            : 
      61                 :          0 :         return 0;
      62                 :            : }
      63                 :            : 
      64                 :            : /*
      65                 :            :  * Read the MMP block. It _must_ be read from disk and hence we clear the
      66                 :            :  * uptodate flag on the buffer.
      67                 :            :  */
      68                 :          0 : static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
      69                 :            :                           ext4_fsblk_t mmp_block)
      70                 :            : {
      71                 :            :         struct mmp_struct *mmp;
      72                 :            :         int ret;
      73                 :            : 
      74         [ #  # ]:          0 :         if (*bh)
      75                 :            :                 clear_buffer_uptodate(*bh);
      76                 :            : 
      77                 :            :         /* This would be sb_bread(sb, mmp_block), except we need to be sure
      78                 :            :          * that the MD RAID device cache has been bypassed, and that the read
      79                 :            :          * is not blocked in the elevator. */
      80         [ #  # ]:          0 :         if (!*bh) {
      81                 :          0 :                 *bh = sb_getblk(sb, mmp_block);
      82         [ #  # ]:          0 :                 if (!*bh) {
      83                 :            :                         ret = -ENOMEM;
      84                 :            :                         goto warn_exit;
      85                 :            :                 }
      86                 :            :         }
      87                 :            : 
      88                 :          0 :         get_bh(*bh);
      89                 :          0 :         lock_buffer(*bh);
      90                 :          0 :         (*bh)->b_end_io = end_buffer_read_sync;
      91                 :          0 :         submit_bh(REQ_OP_READ, REQ_META | REQ_PRIO, *bh);
      92                 :          0 :         wait_on_buffer(*bh);
      93         [ #  # ]:          0 :         if (!buffer_uptodate(*bh)) {
      94                 :            :                 ret = -EIO;
      95                 :            :                 goto warn_exit;
      96                 :            :         }
      97                 :          0 :         mmp = (struct mmp_struct *)((*bh)->b_data);
      98         [ #  # ]:          0 :         if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC) {
      99                 :            :                 ret = -EFSCORRUPTED;
     100                 :            :                 goto warn_exit;
     101                 :            :         }
     102         [ #  # ]:          0 :         if (!ext4_mmp_csum_verify(sb, mmp)) {
     103                 :            :                 ret = -EFSBADCRC;
     104                 :            :                 goto warn_exit;
     105                 :            :         }
     106                 :            :         return 0;
     107                 :            : warn_exit:
     108                 :          0 :         brelse(*bh);
     109                 :          0 :         *bh = NULL;
     110                 :          0 :         ext4_warning(sb, "Error %d while reading MMP block %llu",
     111                 :            :                      ret, mmp_block);
     112                 :          0 :         return ret;
     113                 :            : }
     114                 :            : 
     115                 :            : /*
     116                 :            :  * Dump as much information as possible to help the admin.
     117                 :            :  */
     118                 :          0 : void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
     119                 :            :                     const char *function, unsigned int line, const char *msg)
     120                 :            : {
     121                 :          0 :         __ext4_warning(sb, function, line, "%s", msg);
     122                 :          0 :         __ext4_warning(sb, function, line,
     123                 :            :                        "MMP failure info: last update time: %llu, last update node: %.*s, last update device: %.*s",
     124                 :            :                        (unsigned long long)le64_to_cpu(mmp->mmp_time),
     125                 :          0 :                        (int)sizeof(mmp->mmp_nodename), mmp->mmp_nodename,
     126                 :          0 :                        (int)sizeof(mmp->mmp_bdevname), mmp->mmp_bdevname);
     127                 :          0 : }
     128                 :            : 
     129                 :            : /*
     130                 :            :  * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
     131                 :            :  */
     132                 :          0 : static int kmmpd(void *data)
     133                 :            : {
     134                 :          0 :         struct super_block *sb = ((struct mmpd_data *) data)->sb;
     135                 :          0 :         struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
     136                 :          0 :         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
     137                 :            :         struct mmp_struct *mmp;
     138                 :            :         ext4_fsblk_t mmp_block;
     139                 :            :         u32 seq = 0;
     140                 :            :         unsigned long failed_writes = 0;
     141                 :          0 :         int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
     142                 :            :         unsigned mmp_check_interval;
     143                 :            :         unsigned long last_update_time;
     144                 :            :         unsigned long diff;
     145                 :            :         int retval;
     146                 :            : 
     147                 :          0 :         mmp_block = le64_to_cpu(es->s_mmp_block);
     148                 :          0 :         mmp = (struct mmp_struct *)(bh->b_data);
     149                 :          0 :         mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
     150                 :            :         /*
     151                 :            :          * Start with the higher mmp_check_interval and reduce it if
     152                 :            :          * the MMP block is being updated on time.
     153                 :            :          */
     154                 :          0 :         mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
     155                 :            :                                  EXT4_MMP_MIN_CHECK_INTERVAL);
     156                 :          0 :         mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
     157                 :            :         BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
     158                 :          0 :         bdevname(bh->b_bdev, mmp->mmp_bdevname);
     159                 :            : 
     160                 :          0 :         memcpy(mmp->mmp_nodename, init_utsname()->nodename,
     161                 :            :                sizeof(mmp->mmp_nodename));
     162                 :            : 
     163         [ #  # ]:          0 :         while (!kthread_should_stop()) {
     164         [ #  # ]:          0 :                 if (++seq > EXT4_MMP_SEQ_MAX)
     165                 :            :                         seq = 1;
     166                 :            : 
     167                 :          0 :                 mmp->mmp_seq = cpu_to_le32(seq);
     168                 :          0 :                 mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
     169                 :          0 :                 last_update_time = jiffies;
     170                 :            : 
     171                 :          0 :                 retval = write_mmp_block(sb, bh);
     172                 :            :                 /*
     173                 :            :                  * Don't spew too many error messages. Print one every
     174                 :            :                  * (s_mmp_update_interval * 60) seconds.
     175                 :            :                  */
     176         [ #  # ]:          0 :                 if (retval) {
     177         [ #  # ]:          0 :                         if ((failed_writes % 60) == 0)
     178                 :          0 :                                 ext4_error(sb, "Error writing to MMP block");
     179                 :          0 :                         failed_writes++;
     180                 :            :                 }
     181                 :            : 
     182         [ #  # ]:          0 :                 if (!(le32_to_cpu(es->s_feature_incompat) &
     183                 :            :                     EXT4_FEATURE_INCOMPAT_MMP)) {
     184                 :          0 :                         ext4_warning(sb, "kmmpd being stopped since MMP feature"
     185                 :            :                                      " has been disabled.");
     186                 :          0 :                         goto exit_thread;
     187                 :            :                 }
     188                 :            : 
     189         [ #  # ]:          0 :                 if (sb_rdonly(sb))
     190                 :            :                         break;
     191                 :            : 
     192                 :          0 :                 diff = jiffies - last_update_time;
     193         [ #  # ]:          0 :                 if (diff < mmp_update_interval * HZ)
     194                 :          0 :                         schedule_timeout_interruptible(mmp_update_interval *
     195                 :          0 :                                                        HZ - diff);
     196                 :            : 
     197                 :            :                 /*
     198                 :            :                  * We need to make sure that more than mmp_check_interval
     199                 :            :                  * seconds have not passed since writing. If that has happened
     200                 :            :                  * we need to check if the MMP block is as we left it.
     201                 :            :                  */
     202                 :          0 :                 diff = jiffies - last_update_time;
     203         [ #  # ]:          0 :                 if (diff > mmp_check_interval * HZ) {
     204                 :          0 :                         struct buffer_head *bh_check = NULL;
     205                 :            :                         struct mmp_struct *mmp_check;
     206                 :            : 
     207                 :          0 :                         retval = read_mmp_block(sb, &bh_check, mmp_block);
     208         [ #  # ]:          0 :                         if (retval) {
     209                 :          0 :                                 ext4_error(sb, "error reading MMP data: %d",
     210                 :            :                                            retval);
     211                 :          0 :                                 goto exit_thread;
     212                 :            :                         }
     213                 :            : 
     214                 :          0 :                         mmp_check = (struct mmp_struct *)(bh_check->b_data);
     215   [ #  #  #  # ]:          0 :                         if (mmp->mmp_seq != mmp_check->mmp_seq ||
     216                 :          0 :                             memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
     217                 :            :                                    sizeof(mmp->mmp_nodename))) {
     218                 :          0 :                                 dump_mmp_msg(sb, mmp_check,
     219                 :            :                                              "Error while updating MMP info. "
     220                 :            :                                              "The filesystem seems to have been"
     221                 :            :                                              " multiply mounted.");
     222                 :          0 :                                 ext4_error(sb, "abort");
     223                 :          0 :                                 put_bh(bh_check);
     224                 :            :                                 retval = -EBUSY;
     225                 :          0 :                                 goto exit_thread;
     226                 :            :                         }
     227                 :          0 :                         put_bh(bh_check);
     228                 :            :                 }
     229                 :            : 
     230                 :            :                  /*
     231                 :            :                  * Adjust the mmp_check_interval depending on how much time
     232                 :            :                  * it took for the MMP block to be written.
     233                 :            :                  */
     234                 :          0 :                 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
     235                 :            :                                              EXT4_MMP_MAX_CHECK_INTERVAL),
     236                 :            :                                          EXT4_MMP_MIN_CHECK_INTERVAL);
     237                 :          0 :                 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
     238                 :            :         }
     239                 :            : 
     240                 :            :         /*
     241                 :            :          * Unmount seems to be clean.
     242                 :            :          */
     243                 :          0 :         mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
     244                 :          0 :         mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds());
     245                 :            : 
     246                 :          0 :         retval = write_mmp_block(sb, bh);
     247                 :            : 
     248                 :            : exit_thread:
     249                 :          0 :         EXT4_SB(sb)->s_mmp_tsk = NULL;
     250                 :          0 :         kfree(data);
     251                 :            :         brelse(bh);
     252                 :          0 :         return retval;
     253                 :            : }
     254                 :            : 
     255                 :            : /*
     256                 :            :  * Get a random new sequence number but make sure it is not greater than
     257                 :            :  * EXT4_MMP_SEQ_MAX.
     258                 :            :  */
     259                 :            : static unsigned int mmp_new_seq(void)
     260                 :            : {
     261                 :            :         u32 new_seq;
     262                 :            : 
     263                 :            :         do {
     264                 :          0 :                 new_seq = prandom_u32();
     265         [ #  # ]:          0 :         } while (new_seq > EXT4_MMP_SEQ_MAX);
     266                 :            : 
     267                 :          0 :         return new_seq;
     268                 :            : }
     269                 :            : 
     270                 :            : /*
     271                 :            :  * Protect the filesystem from being mounted more than once.
     272                 :            :  */
     273                 :          0 : int ext4_multi_mount_protect(struct super_block *sb,
     274                 :            :                                     ext4_fsblk_t mmp_block)
     275                 :            : {
     276                 :          0 :         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
     277                 :          0 :         struct buffer_head *bh = NULL;
     278                 :            :         struct mmp_struct *mmp = NULL;
     279                 :            :         struct mmpd_data *mmpd_data;
     280                 :            :         u32 seq;
     281                 :          0 :         unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
     282                 :            :         unsigned int wait_time = 0;
     283                 :            :         int retval;
     284                 :            : 
     285   [ #  #  #  # ]:          0 :         if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
     286                 :            :             mmp_block >= ext4_blocks_count(es)) {
     287                 :          0 :                 ext4_warning(sb, "Invalid MMP block in superblock");
     288                 :          0 :                 goto failed;
     289                 :            :         }
     290                 :            : 
     291                 :          0 :         retval = read_mmp_block(sb, &bh, mmp_block);
     292         [ #  # ]:          0 :         if (retval)
     293                 :            :                 goto failed;
     294                 :            : 
     295                 :          0 :         mmp = (struct mmp_struct *)(bh->b_data);
     296                 :            : 
     297         [ #  # ]:          0 :         if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
     298                 :            :                 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
     299                 :            : 
     300                 :            :         /*
     301                 :            :          * If check_interval in MMP block is larger, use that instead of
     302                 :            :          * update_interval from the superblock.
     303                 :            :          */
     304         [ #  # ]:          0 :         if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval)
     305                 :            :                 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval);
     306                 :            : 
     307                 :          0 :         seq = le32_to_cpu(mmp->mmp_seq);
     308         [ #  # ]:          0 :         if (seq == EXT4_MMP_SEQ_CLEAN)
     309                 :            :                 goto skip;
     310                 :            : 
     311         [ #  # ]:          0 :         if (seq == EXT4_MMP_SEQ_FSCK) {
     312                 :          0 :                 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
     313                 :          0 :                 goto failed;
     314                 :            :         }
     315                 :            : 
     316                 :          0 :         wait_time = min(mmp_check_interval * 2 + 1,
     317                 :            :                         mmp_check_interval + 60);
     318                 :            : 
     319                 :            :         /* Print MMP interval if more than 20 secs. */
     320         [ #  # ]:          0 :         if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
     321                 :          0 :                 ext4_warning(sb, "MMP interval %u higher than expected, please"
     322                 :            :                              " wait.\n", wait_time * 2);
     323                 :            : 
     324         [ #  # ]:          0 :         if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
     325                 :          0 :                 ext4_warning(sb, "MMP startup interrupted, failing mount\n");
     326                 :          0 :                 goto failed;
     327                 :            :         }
     328                 :            : 
     329                 :          0 :         retval = read_mmp_block(sb, &bh, mmp_block);
     330         [ #  # ]:          0 :         if (retval)
     331                 :            :                 goto failed;
     332                 :          0 :         mmp = (struct mmp_struct *)(bh->b_data);
     333         [ #  # ]:          0 :         if (seq != le32_to_cpu(mmp->mmp_seq)) {
     334                 :          0 :                 dump_mmp_msg(sb, mmp,
     335                 :            :                              "Device is already active on another node.");
     336                 :          0 :                 goto failed;
     337                 :            :         }
     338                 :            : 
     339                 :            : skip:
     340                 :            :         /*
     341                 :            :          * write a new random sequence number.
     342                 :            :          */
     343                 :            :         seq = mmp_new_seq();
     344                 :          0 :         mmp->mmp_seq = cpu_to_le32(seq);
     345                 :            : 
     346                 :          0 :         retval = write_mmp_block(sb, bh);
     347         [ #  # ]:          0 :         if (retval)
     348                 :            :                 goto failed;
     349                 :            : 
     350                 :            :         /*
     351                 :            :          * wait for MMP interval and check mmp_seq.
     352                 :            :          */
     353         [ #  # ]:          0 :         if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
     354                 :          0 :                 ext4_warning(sb, "MMP startup interrupted, failing mount");
     355                 :          0 :                 goto failed;
     356                 :            :         }
     357                 :            : 
     358                 :          0 :         retval = read_mmp_block(sb, &bh, mmp_block);
     359         [ #  # ]:          0 :         if (retval)
     360                 :            :                 goto failed;
     361                 :          0 :         mmp = (struct mmp_struct *)(bh->b_data);
     362         [ #  # ]:          0 :         if (seq != le32_to_cpu(mmp->mmp_seq)) {
     363                 :          0 :                 dump_mmp_msg(sb, mmp,
     364                 :            :                              "Device is already active on another node.");
     365                 :          0 :                 goto failed;
     366                 :            :         }
     367                 :            : 
     368                 :            :         mmpd_data = kmalloc(sizeof(*mmpd_data), GFP_KERNEL);
     369         [ #  # ]:          0 :         if (!mmpd_data) {
     370                 :          0 :                 ext4_warning(sb, "not enough memory for mmpd_data");
     371                 :          0 :                 goto failed;
     372                 :            :         }
     373                 :          0 :         mmpd_data->sb = sb;
     374                 :          0 :         mmpd_data->bh = bh;
     375                 :            : 
     376                 :            :         /*
     377                 :            :          * Start a kernel thread to update the MMP block periodically.
     378                 :            :          */
     379         [ #  # ]:          0 :         EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%.*s",
     380                 :            :                                              (int)sizeof(mmp->mmp_bdevname),
     381                 :            :                                              bdevname(bh->b_bdev,
     382                 :            :                                                       mmp->mmp_bdevname));
     383         [ #  # ]:          0 :         if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
     384                 :          0 :                 EXT4_SB(sb)->s_mmp_tsk = NULL;
     385                 :          0 :                 kfree(mmpd_data);
     386                 :          0 :                 ext4_warning(sb, "Unable to create kmmpd thread for %s.",
     387                 :            :                              sb->s_id);
     388                 :          0 :                 goto failed;
     389                 :            :         }
     390                 :            : 
     391                 :            :         return 0;
     392                 :            : 
     393                 :            : failed:
     394                 :          0 :         brelse(bh);
     395                 :            :         return 1;
     396                 :            : }
     397                 :            : 
     398                 :            : 

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