[PATCH] ext4, jbd2: abort journal on file data write error under data_err=abort

[Aditya Srivastava <aditya.ansh182@gmail.com>]

From: Aditya Prakash Srivastava <aditya.ansh182@gmail.com>

The "data_err=abort" mount option in ext4 is designed to abort the
journal and force the filesystem into read-only mode if a file data
writeback failure is detected (to prevent silent data loss and stale
data exposure).

However, in standard data=ordered mode, file data writeback is executed
and waited for during transaction commit in
journal_finish_inode_data_buffers(). When
filemap_fdatawait_range_keep_errors() detects and returns a data writeback
error (e.g. -EIO), JBD2 merely prints a warning message and then
discards the error. This results in the transaction committing
successfully, exposing stale/corrupted data and defeating the purpose
of the data_err=abort option.

Fix this by:
1. Defining a new JBD2 configuration flag, JBD2_ABORT_ON_DATA_ERR.
2. In JBD2, if JBD2_ABORT_ON_DATA_ERR is set, abort the transaction commit
   and the journal thread via jbd2_journal_abort() if writeback fails.
3. In ext4, configure JBD2_ABORT_ON_DATA_ERR on the journal based on the
   ext4 "data_err=abort" mount option in ext4_init_journal_params().

Reported-by: Anthony Rebello <arebello@redhat.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=207729
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Aditya Prakash Srivastava <aditya.ansh182@gmail.com>
---
 fs/ext4/super.c      | 4 ++++
 fs/jbd2/commit.c     | 2 ++
 include/linux/jbd2.h | 1 +
 3 files changed, 7 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7283108d7609..de34490a5b68 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5875,6 +5875,10 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
 		journal->j_flags |= JBD2_BARRIER;
 	else
 		journal->j_flags &= ~JBD2_BARRIER;
+	if (test_opt(sb, DATA_ERR_ABORT))
+		journal->j_flags |= JBD2_ABORT_ON_DATA_ERR;
+	else
+		journal->j_flags &= ~JBD2_ABORT_ON_DATA_ERR;
 	/*
 	 * Always enable journal cycle record option, letting the journal
 	 * records log transactions continuously between each mount.
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index d8577725a2fb..49acc9d0809e 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -768,6 +768,8 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 		printk(KERN_WARNING
 			"JBD2: Detected IO errors %d while flushing file data on %s\n",
 			err, journal->j_devname);
+		if (journal->j_flags & JBD2_ABORT_ON_DATA_ERR)
+			jbd2_journal_abort(journal, err);
 		err = 0;
 	}
 
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 7e785aa6d35d..e39679656de6 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1410,6 +1410,7 @@ JBD2_FEATURE_INCOMPAT_FUNCS(fast_commit,	FAST_COMMIT)
 #define JBD2_FLUSHED	0x008	/* The journal superblock has been flushed */
 #define JBD2_LOADED	0x010	/* The journal superblock has been loaded */
 #define JBD2_BARRIER	0x020	/* Use IDE barriers */
+#define JBD2_ABORT_ON_DATA_ERR	0x040	/* Abort the journal on file data write errors */
 #define JBD2_CYCLE_RECORD		0x080	/* Journal cycled record log on
 						 * clean and empty filesystem
 						 * logging area */
-- 
2.47.3