2015-10-12 02:19:06

by Daeho Jeong

Subject: [PATCH v2] ext4, jbd2: ensure entering into panic after recording an error in superblock

If a EXT4 filesystem utilizes JBD2 journaling and an error occurs, the
journaling will be aborted first and the error number will be recorded
into JBD2 superblock and, finally, the system will enter into the
panic state in "errors=panic" option. But, in the rare case, this
sequence is little twisted like the below figure and it will happen
that the system enters into panic state, which means the system reset
in mobile environment, before completion of recording an error in the
journal superblock. In this case, e2fsck cannot recognize that the
filesystem failure occurred in the previous run and the corruption
wouldn't be fixed.

Task A Task B
ext4_handle_error()
-> jbd2_journal_abort()
-> __journal_abort_soft()
-> __jbd2_journal_abort_hard()
| -> journal->j_flags |= JBD2_ABORT;
|
| __ext4_abort()
| -> jbd2_journal_abort()
| | -> __journal_abort_soft()
| | -> if (journal->j_flags & JBD2_ABORT)
| | return;
| -> panic()
|
-> jbd2_journal_update_sb_errno()

Tested-by: Hobin Woo <[email protected]>
Signed-off-by: Daeho Jeong <[email protected]>
Signed-off-by: Theodore Ts'o <[email protected]>
---
fs/ext4/super.c | 12 ++++++++++--
fs/jbd2/journal.c | 6 +++++-
include/linux/jbd2.h | 1 +
3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ca9d4a2..baecf29 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -380,9 +380,13 @@ static void ext4_handle_error(struct super_block *sb)
smp_wmb();
sb->s_flags |= MS_RDONLY;
}
- if (test_opt(sb, ERRORS_PANIC))
+ 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);
+ }
}

#define ext4_error_ratelimit(sb) \
@@ -571,8 +575,12 @@ void __ext4_abort(struct super_block *sb, const char *function,
jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
save_error_info(sb, function, line);
}
- if (test_opt(sb, ERRORS_PANIC))
+ 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 panic from previous error\n");
+ }
}

void __ext4_msg(struct super_block *sb,
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b96bd80..b7ac9f2 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2053,8 +2053,12 @@ static void __journal_abort_soft (journal_t *journal, int errno)

__jbd2_journal_abort_hard(journal);

- if (errno)
+ if (errno) {
jbd2_journal_update_sb_errno(journal);
+ write_lock(&journal->j_state_lock);
+ journal->j_flags |= JBD2_REC_ERR;
+ write_unlock(&journal->j_state_lock);
+ }
}

/**
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 20e7f78..75f2e85 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1007,6 +1007,7 @@ struct journal_s
#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
--
1.7.9.5

2015-10-18 23:38:08

by Theodore Ts'o

Subject: Re: [PATCH v2] ext4, jbd2: ensure entering into panic after recording an error in superblock

On Mon, Oct 12, 2015 at 11:19:19AM +0900, Daeho Jeong wrote:
> If a EXT4 filesystem utilizes JBD2 journaling and an error occurs, the
> journaling will be aborted first and the error number will be recorded
> into JBD2 superblock and, finally, the system will enter into the
> panic state in "errors=panic" option. But, in the rare case, this
> sequence is little twisted like the below figure and it will happen
> that the system enters into panic state, which means the system reset
> in mobile environment, before completion of recording an error in the
> journal superblock. In this case, e2fsck cannot recognize that the
> filesystem failure occurred in the previous run and the corruption
> wouldn't be fixed.
>
> Task A Task B
> ext4_handle_error()
> -> jbd2_journal_abort()
> -> __journal_abort_soft()
> -> __jbd2_journal_abort_hard()
> | -> journal->j_flags |= JBD2_ABORT;
> |
> | __ext4_abort()
> | -> jbd2_journal_abort()
> | | -> __journal_abort_soft()
> | | -> if (journal->j_flags & JBD2_ABORT)
> | | return;
> | -> panic()
> |
> -> jbd2_journal_update_sb_errno()
>
> Tested-by: Hobin Woo <[email protected]>
> Signed-off-by: Daeho Jeong <[email protected]>
> Signed-off-by: Theodore Ts'o <[email protected]>

Applied, thanks.

- Ted