Date:	Wed, 14 May 2008 13:50:43 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Andrew Morton <akpm@...ux-foundation.org>, sct@...hat.com,
	adilger@...sterfs.com
Cc:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	Jan Kara <jack@...e.cz>, Josef Bacik <jbacik@...hat.com>,
	Mingming Cao <cmm@...ibm.com>,
	Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>,
	sugita <yumiko.sugita.yf@...achi.com>
Subject: [PATCH 4/4] jbd: fix error handling for checkpoint io (rebased)

Subject: [PATCH 4/4] jbd: fix error handling for checkpoint io

When a checkpointing IO fails, current JBD code doesn't check the
error and continue journaling.  This means latest metadata can be
lost from both the journal and filesystem.

This patch leaves the failed metadata blocks in the journal space
and aborts journaling in the case of log_do_checkpoint().
To achieve this, we need to do:

1. don't remove the failed buffer from the checkpoint list where in
   the case of __try_to_free_cp_buf() because it may be released or
   overwritten by a later transaction
2. log_do_checkpoint() is the last chance, remove the failed buffer
   from the checkpoint list and abort journaling
3. when checkpointing fails, don't update the journal super block to
   prevent the journalled contents from being cleaned
4. when checkpointing fails, don't clear the needs_recovery flag,
   otherwise the journalled contents are ignored and cleaned in the
   recovery phase
5. if the recovery fails, keep the needs_recovery flag

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
---
 fs/ext3/ioctl.c     |   12 ++++----
 fs/ext3/super.c     |   13 +++++++--
 fs/jbd/checkpoint.c |   59 ++++++++++++++++++++++++++++++++++--------
 fs/jbd/journal.c    |   21 +++++++++-----
 fs/jbd/recovery.c   |    7 +++-
 include/linux/jbd.h |    7 ++++
 6 files changed, 91 insertions(+), 28 deletions(-)

Index: linux-2.6.26-rc2/fs/jbd/checkpoint.c
===================================================================
--- linux-2.6.26-rc2.orig/fs/jbd/checkpoint.c
+++ linux-2.6.26-rc2/fs/jbd/checkpoint.c
@@ -93,7 +93,8 @@ static int __try_to_free_cp_buf(struct j
 	int ret = 0;
 	struct buffer_head *bh = jh2bh(jh);
 
-	if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) {
+	if (jh->b_jlist == BJ_None && !buffer_locked(bh) &&
+	    !buffer_dirty(bh) && buffer_uptodate(bh)) {
 		JBUFFER_TRACE(jh, "remove from checkpoint list");
 		ret = __journal_remove_checkpoint(jh) + 1;
 		jbd_unlock_bh_state(bh);
@@ -140,6 +141,25 @@ void __log_wait_for_space(journal_t *jou
 }
 
 /*
+ * We couldn't write back some metadata buffers to the filesystem.
+ * To avoid unwritten-back metadata buffers from losing, set
+ * JFS_CP_ABORT flag and make sure that the journal space isn't
+ * cleaned.  This function also aborts journaling.
+ */
+static void __journal_abort_checkpoint(journal_t *journal, int errno)
+{
+	if (is_checkpoint_aborted(journal))
+		return;
+
+	spin_lock(&journal->j_state_lock);
+	journal->j_flags |= JFS_CP_ABORT;
+	spin_unlock(&journal->j_state_lock);
+	printk(KERN_WARNING "JBD: Checkpointing failed.  Some metadata blocks "
+	       "are still old.\n");
+	journal_abort(journal, errno);
+}
+
+/*
  * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
  * The caller must restart a list walk.  Wait for someone else to run
  * jbd_unlock_bh_state().
@@ -160,21 +180,25 @@ static void jbd_sync_bh(journal_t *journ
  * buffers. Note that we take the buffers in the opposite ordering
  * from the one in which they were submitted for IO.
  *
+ * Return 0 on success, and return <0 if some buffers have failed
+ * to be written out.
+ *
  * Called with j_list_lock held.
  */
-static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
+static int __wait_cp_io(journal_t *journal, transaction_t *transaction)
 {
 	struct journal_head *jh;
 	struct buffer_head *bh;
 	tid_t this_tid;
 	int released = 0;
+	int ret = 0;
 
 	this_tid = transaction->t_tid;
 restart:
 	/* Did somebody clean up the transaction in the meanwhile? */
 	if (journal->j_checkpoint_transactions != transaction ||
 			transaction->t_tid != this_tid)
-		return;
+		return ret;
 	while (!released && transaction->t_checkpoint_io_list) {
 		jh = transaction->t_checkpoint_io_list;
 		bh = jh2bh(jh);
@@ -194,6 +218,9 @@ restart:
 			spin_lock(&journal->j_list_lock);
 			goto restart;
 		}
+		if (unlikely(!buffer_uptodate(bh)))
+			ret = -EIO;
+
 		/*
 		 * Now in whatever state the buffer currently is, we know that
 		 * it has been written out and so we can drop it from the list
@@ -203,6 +230,8 @@ restart:
 		journal_remove_journal_head(bh);
 		__brelse(bh);
 	}
+
+	return ret;
 }
 
 #define NR_BATCH	64
@@ -226,7 +255,8 @@ __flush_batch(journal_t *journal, struct
  * Try to flush one buffer from the checkpoint list to disk.
  *
  * Return 1 if something happened which requires us to abort the current
- * scan of the checkpoint list.
+ * scan of the checkpoint list.  Return <0 if the buffer has failed to
+ * be written out.
  *
  * Called with j_list_lock held and drops it if 1 is returned
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
@@ -256,6 +286,9 @@ static int __process_buffer(journal_t *j
 		log_wait_commit(journal, tid);
 		ret = 1;
 	} else if (!buffer_dirty(bh)) {
+		ret = 1;
+		if (unlikely(!buffer_uptodate(bh)))
+			ret = -EIO;
 		J_ASSERT_JH(jh, !buffer_jbddirty(bh));
 		BUFFER_TRACE(bh, "remove from checkpoint");
 		__journal_remove_checkpoint(jh);
@@ -263,7 +296,6 @@ static int __process_buffer(journal_t *j
 		jbd_unlock_bh_state(bh);
 		journal_remove_journal_head(bh);
 		__brelse(bh);
-		ret = 1;
 	} else {
 		/*
 		 * Important: we are about to write the buffer, and
@@ -318,6 +350,7 @@ int log_do_checkpoint(journal_t *journal
 	 * OK, we need to start writing disk blocks.  Take one transaction
 	 * and write it.
 	 */
+	result = 0;
 	spin_lock(&journal->j_list_lock);
 	if (!journal->j_checkpoint_transactions)
 		goto out;
@@ -334,7 +367,7 @@ restart:
 		int batch_count = 0;
 		struct buffer_head *bhs[NR_BATCH];
 		struct journal_head *jh;
-		int retry = 0;
+		int retry = 0, err;
 
 		while (!retry && transaction->t_checkpoint_list) {
 			struct buffer_head *bh;
@@ -347,6 +380,8 @@ restart:
 				break;
 			}
 			retry = __process_buffer(journal, jh, bhs,&batch_count);
+			if (retry < 0)
+				result = retry;
 			if (!retry && (need_resched() ||
 				spin_needbreak(&journal->j_list_lock))) {
 				spin_unlock(&journal->j_list_lock);
@@ -371,14 +406,18 @@ restart:
 		 * Now we have cleaned up the first transaction's checkpoint
 		 * list. Let's clean up the second one
 		 */
-		__wait_cp_io(journal, transaction);
+		err = __wait_cp_io(journal, transaction);
+		if (!result)
+			result = err;
 	}
 out:
 	spin_unlock(&journal->j_list_lock);
-	result = cleanup_journal_tail(journal);
 	if (result < 0)
-		return result;
-	return 0;
+		__journal_abort_checkpoint(journal, result);
+	else
+		result = cleanup_journal_tail(journal);
+
+	return (result < 0) ? result : 0;
 }
 
 /*
Index: linux-2.6.26-rc2/include/linux/jbd.h
===================================================================
--- linux-2.6.26-rc2.orig/include/linux/jbd.h
+++ linux-2.6.26-rc2/include/linux/jbd.h
@@ -816,6 +816,8 @@ struct journal_s
 #define JFS_FLUSHED	0x008	/* The journal superblock has been flushed */
 #define JFS_LOADED	0x010	/* The journal superblock has been loaded */
 #define JFS_BARRIER	0x020	/* Use IDE barriers */
+#define JFS_CP_ABORT	0x040	/* Checkpointing has failed.  We don't have to
+				 * clean the journal space.  */
 
 /*
  * Function declarations for the journaling transaction and buffer
@@ -1004,6 +1006,11 @@ static inline int is_journal_aborted(jou
 	return journal->j_flags & JFS_ABORT;
 }
 
+static inline int is_checkpoint_aborted(journal_t *journal)
+{
+	return journal->j_flags & JFS_CP_ABORT;
+}
+
 static inline int is_handle_aborted(handle_t *handle)
 {
 	if (handle->h_aborted)
Index: linux-2.6.26-rc2/fs/ext3/ioctl.c
===================================================================
--- linux-2.6.26-rc2.orig/fs/ext3/ioctl.c
+++ linux-2.6.26-rc2/fs/ext3/ioctl.c
@@ -239,7 +239,7 @@ setrsvsz_out:
 	case EXT3_IOC_GROUP_EXTEND: {
 		ext3_fsblk_t n_blocks_count;
 		struct super_block *sb = inode->i_sb;
-		int err;
+		int err, err2;
 
 		if (!capable(CAP_SYS_RESOURCE))
 			return -EPERM;
@@ -254,16 +254,16 @@ setrsvsz_out:
 		}
 		err = ext3_group_extend(sb, EXT3_SB(sb)->s_es, n_blocks_count);
 		journal_lock_updates(EXT3_SB(sb)->s_journal);
-		journal_flush(EXT3_SB(sb)->s_journal);
+		err2 = journal_flush(EXT3_SB(sb)->s_journal);
 		journal_unlock_updates(EXT3_SB(sb)->s_journal);
 group_extend_out:
 		mnt_drop_write(filp->f_path.mnt);
-		return err;
+		return (err) ? err : err2;
 	}
 	case EXT3_IOC_GROUP_ADD: {
 		struct ext3_new_group_data input;
 		struct super_block *sb = inode->i_sb;
-		int err;
+		int err, err2;
 
 		if (!capable(CAP_SYS_RESOURCE))
 			return -EPERM;
@@ -280,11 +280,11 @@ group_extend_out:
 
 		err = ext3_group_add(sb, &input);
 		journal_lock_updates(EXT3_SB(sb)->s_journal);
-		journal_flush(EXT3_SB(sb)->s_journal);
+		err2 = journal_flush(EXT3_SB(sb)->s_journal);
 		journal_unlock_updates(EXT3_SB(sb)->s_journal);
 group_add_out:
 		mnt_drop_write(filp->f_path.mnt);
-		return err;
+		return (err) ? err : err2;
 	}
 
 
Index: linux-2.6.26-rc2/fs/ext3/super.c
===================================================================
--- linux-2.6.26-rc2.orig/fs/ext3/super.c
+++ linux-2.6.26-rc2/fs/ext3/super.c
@@ -395,7 +395,10 @@ static void ext3_put_super (struct super
 	ext3_xattr_put_super(sb);
 	journal_destroy(sbi->s_journal);
 	if (!(sb->s_flags & MS_RDONLY)) {
-		EXT3_CLEAR_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_RECOVER);
+		if (!is_checkpoint_aborted(sbi->s_journal)) {
+			EXT3_CLEAR_INCOMPAT_FEATURE(sb,
+				EXT3_FEATURE_INCOMPAT_RECOVER);
+		}
 		es->s_state = cpu_to_le16(sbi->s_mount_state);
 		BUFFER_TRACE(sbi->s_sbh, "marking dirty");
 		mark_buffer_dirty(sbi->s_sbh);
@@ -2373,7 +2376,13 @@ static void ext3_write_super_lockfs(stru
 
 		/* Now we set up the journal barrier. */
 		journal_lock_updates(journal);
-		journal_flush(journal);
+
+		/*
+		 * We don't want to clear needs_recovery flag when we failed
+		 * to flush the journal.
+		 */
+		if (journal_flush(journal) < 0)
+			return;
 
 		/* Journal blocked and flushed, clear needs_recovery flag. */
 		EXT3_CLEAR_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_RECOVER);
Index: linux-2.6.26-rc2/fs/jbd/journal.c
===================================================================
--- linux-2.6.26-rc2.orig/fs/jbd/journal.c
+++ linux-2.6.26-rc2/fs/jbd/journal.c
@@ -674,7 +674,7 @@ static journal_t * journal_init_common (
 	journal->j_commit_interval = (HZ * JBD_DEFAULT_MAX_COMMIT_AGE);
 
 	/* The journal is marked for error until we succeed with recovery! */
-	journal->j_flags = JFS_ABORT;
+	journal->j_flags = JFS_ABORT | JFS_CP_ABORT;
 
 	/* Set up a default-sized revoke table for the new mount. */
 	err = journal_init_revoke(journal, JOURNAL_REVOKE_DEFAULT_HASH);
@@ -1107,7 +1107,7 @@ int journal_load(journal_t *journal)
 	if (journal_reset(journal))
 		goto recovery_error;
 
-	journal->j_flags &= ~JFS_ABORT;
+	journal->j_flags &= ~(JFS_ABORT | JFS_CP_ABORT);
 	journal->j_flags |= JFS_LOADED;
 	return 0;
 
@@ -1151,7 +1151,8 @@ void journal_destroy(journal_t *journal)
 	journal->j_tail = 0;
 	journal->j_tail_sequence = ++journal->j_transaction_sequence;
 	if (journal->j_sb_buffer) {
-		journal_update_superblock(journal, 1);
+		if (!is_checkpoint_aborted(journal))
+			journal_update_superblock(journal, 1);
 		brelse(journal->j_sb_buffer);
 	}
 
@@ -1333,7 +1334,6 @@ static int journal_convert_superblock_v1
 
 int journal_flush(journal_t *journal)
 {
-	int err = 0;
 	transaction_t *transaction = NULL;
 	unsigned long old_tail;
 
@@ -1356,14 +1356,19 @@ int journal_flush(journal_t *journal)
 		spin_unlock(&journal->j_state_lock);
 	}
 
-	/* ...and flush everything in the log out to disk. */
+	/* ...and flush everything in the log out to disk.
+	 * Even if an error occurs, we don't stop this loop.
+	 * We do checkpoint as much as possible.  */
 	spin_lock(&journal->j_list_lock);
-	while (!err && journal->j_checkpoint_transactions != NULL) {
+	while (journal->j_checkpoint_transactions != NULL) {
 		spin_unlock(&journal->j_list_lock);
-		err = log_do_checkpoint(journal);
+		log_do_checkpoint(journal);
 		spin_lock(&journal->j_list_lock);
 	}
 	spin_unlock(&journal->j_list_lock);
+	if (is_checkpoint_aborted(journal))
+		return -EIO;
+
 	cleanup_journal_tail(journal);
 
 	/* Finally, mark the journal as really needing no recovery.
@@ -1385,7 +1390,7 @@ int journal_flush(journal_t *journal)
 	J_ASSERT(journal->j_head == journal->j_tail);
 	J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
 	spin_unlock(&journal->j_state_lock);
-	return err;
+	return 0;
 }
 
 /**
Index: linux-2.6.26-rc2/fs/jbd/recovery.c
===================================================================
--- linux-2.6.26-rc2.orig/fs/jbd/recovery.c
+++ linux-2.6.26-rc2/fs/jbd/recovery.c
@@ -223,7 +223,7 @@ do {									\
  */
 int journal_recover(journal_t *journal)
 {
-	int			err;
+	int			err, err2;
 	journal_superblock_t *	sb;
 
 	struct recovery_info	info;
@@ -261,7 +261,10 @@ int journal_recover(journal_t *journal)
 	journal->j_transaction_sequence = ++info.end_transaction;
 
 	journal_clear_revoke(journal);
-	sync_blockdev(journal->j_fs_dev);
+	err2 = sync_blockdev(journal->j_fs_dev);
+	if (!err)
+		err = err2;
+
 	return err;
 }
 


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