Commit 7b97d868 authored by zhangyi (F)'s avatar zhangyi (F) Committed by Theodore Ts'o

ext4, jbd2: ensure panic by fix a race between jbd2 abort and ext4 error handlers

In the ext4 filesystem with errors=panic, if one process is recording
errno in the superblock when invoking jbd2_journal_abort() due to some
error cases, it could be raced by another __ext4_abort() which is
setting the SB_RDONLY flag but missing panic because errno has not been
recorded.

jbd2_journal_commit_transaction()
 jbd2_journal_abort()
  journal->j_flags |= JBD2_ABORT;
  jbd2_journal_update_sb_errno()
                                    | ext4_journal_check_start()
                                    |  __ext4_abort()
                                    |   sb->s_flags |= SB_RDONLY;
                                    |   if (!JBD2_REC_ERR)
                                    |        return;
  journal->j_flags |= JBD2_REC_ERR;

Finally, it will no longer trigger panic because the filesystem has
already been set read-only. Fix this by introduce j_abort_mutex to make
sure journal abort is completed before panic, and remove JBD2_REC_ERR
flag.

Fixes: 4327ba52 ("ext4, jbd2: ensure entering into panic after recording an error in superblock")
Signed-off-by: default avatarzhangyi (F) <yi.zhang@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200609073540.3810702-1-yi.zhang@huawei.comSigned-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 88ee9d57
......@@ -522,9 +522,6 @@ static void ext4_handle_error(struct super_block *sb)
smp_wmb();
sb->s_flags |= SB_RDONLY;
} else if (test_opt(sb, ERRORS_PANIC)) {
if (EXT4_SB(sb)->s_journal &&
!(EXT4_SB(sb)->s_journal->j_flags & JBD2_REC_ERR))
return;
panic("EXT4-fs (device %s): panic forced after error\n",
sb->s_id);
}
......@@ -725,23 +722,20 @@ void __ext4_abort(struct super_block *sb, const char *function,
va_end(args);
if (sb_rdonly(sb) == 0) {
ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED;
if (EXT4_SB(sb)->s_journal)
jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
/*
* Make sure updated value of ->s_mount_flags will be visible
* before ->s_flags update
*/
smp_wmb();
sb->s_flags |= SB_RDONLY;
if (EXT4_SB(sb)->s_journal)
jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
}
if (test_opt(sb, ERRORS_PANIC) && !system_going_down()) {
if (EXT4_SB(sb)->s_journal &&
!(EXT4_SB(sb)->s_journal->j_flags & JBD2_REC_ERR))
return;
if (test_opt(sb, ERRORS_PANIC) && !system_going_down())
panic("EXT4-fs panic from previous error\n");
}
}
void __ext4_msg(struct super_block *sb,
......
......@@ -1140,6 +1140,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
init_waitqueue_head(&journal->j_wait_commit);
init_waitqueue_head(&journal->j_wait_updates);
init_waitqueue_head(&journal->j_wait_reserved);
mutex_init(&journal->j_abort_mutex);
mutex_init(&journal->j_barrier);
mutex_init(&journal->j_checkpoint_mutex);
spin_lock_init(&journal->j_revoke_lock);
......@@ -1402,7 +1403,8 @@ static int jbd2_write_superblock(journal_t *journal, int write_flags)
printk(KERN_ERR "JBD2: Error %d detected when updating "
"journal superblock for %s.\n", ret,
journal->j_devname);
jbd2_journal_abort(journal, ret);
if (!is_journal_aborted(journal))
jbd2_journal_abort(journal, ret);
}
return ret;
......@@ -2153,6 +2155,13 @@ void jbd2_journal_abort(journal_t *journal, int errno)
{
transaction_t *transaction;
/*
* Lock the aborting procedure until everything is done, this avoid
* races between filesystem's error handling flow (e.g. ext4_abort()),
* ensure panic after the error info is written into journal's
* superblock.
*/
mutex_lock(&journal->j_abort_mutex);
/*
* ESHUTDOWN always takes precedence because a file system check
* caused by any other journal abort error is not required after
......@@ -2167,6 +2176,7 @@ void jbd2_journal_abort(journal_t *journal, int errno)
journal->j_errno = errno;
jbd2_journal_update_sb_errno(journal);
}
mutex_unlock(&journal->j_abort_mutex);
return;
}
......@@ -2188,10 +2198,7 @@ void jbd2_journal_abort(journal_t *journal, int errno)
* layer could realise that a filesystem check is needed.
*/
jbd2_journal_update_sb_errno(journal);
write_lock(&journal->j_state_lock);
journal->j_flags |= JBD2_REC_ERR;
write_unlock(&journal->j_state_lock);
mutex_unlock(&journal->j_abort_mutex);
}
/**
......
......@@ -765,6 +765,11 @@ struct journal_s
*/
int j_errno;
/**
* @j_abort_mutex: Lock the whole aborting procedure.
*/
struct mutex j_abort_mutex;
/**
* @j_sb_buffer: The first part of the superblock buffer.
*/
......@@ -1247,7 +1252,6 @@ JBD2_FEATURE_INCOMPAT_FUNCS(csum3, CSUM_V3)
#define JBD2_ABORT_ON_SYNCDATA_ERR 0x040 /* Abort the journal on file
* data write error in ordered
* mode */
#define JBD2_REC_ERR 0x080 /* The errno in the sb has been recorded */
/*
* Function declarations for the journaling transaction and buffer
......
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