[3.16.y-ckt stable] Patch "ext4, jbd2: ensure entering into panic after recording an error in superblock" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ext4, jbd2: ensure entering into panic after recording an error in superblock

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt21.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 6769a9270be72ce63d6139495790175a9250787c Mon Sep 17 00:00:00 2001
From: Daeho Jeong <daeho.jeong at samsung.com>
Date: Sun, 18 Oct 2015 17:02:56 -0400
Subject: ext4, jbd2: ensure entering into panic after recording an error in
 superblock

commit 4327ba52afd03fc4b5afa0ee1d774c9c5b0e85c5 upstream.

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 <hobin.woo at samsung.com>
Signed-off-by: Daeho Jeong <daeho.jeong at samsung.com>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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 a8f6f6a358ce..9b9168705e16 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -405,9 +405,13 @@ 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)					\
@@ -596,8 +600,12 @@ 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 8c649c3f0a80..39c3c2c64740 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2088,8 +2088,12 @@ 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 385593d748f6..e137e962834b 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