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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jan Kara <jack@suse.cz>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 107/241] reiserfs: Make cancel_old_flush() reliable
Date:   Mon, 19 Mar 2018 19:06:12 +0100
Message-Id: <20180319180755.624505421@linuxfoundation.org>
In-Reply-To: <20180319180751.172155436@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@suse.cz>


[ Upstream commit 71b0576bdb862e964a82c73327cdd1a249c53e67 ]

Currently canceling of delayed work that flushes old data using
cancel_old_flush() does not prevent work from being requeued. Thus
in theory new work can be queued after cancel_old_flush() from
reiserfs_freeze() has run. This will become larger problem once
flush_old_commits() can requeue the work itself.

Fix the problem by recording in sbi->work_queue that flushing work is
canceled and should not be requeued.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/reiserfs/journal.c  |    2 +-
 fs/reiserfs/reiserfs.h |    1 +
 fs/reiserfs/super.c    |   21 +++++++++++++++------
 3 files changed, 17 insertions(+), 7 deletions(-)

--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -1959,7 +1959,7 @@ static int do_journal_release(struct rei
 	 * will be requeued because superblock is being shutdown and doesn't
 	 * have MS_ACTIVE set.
 	 */
-	cancel_delayed_work_sync(&REISERFS_SB(sb)->old_work);
+	reiserfs_cancel_old_flush(sb);
 	/* wait for all commits to finish */
 	cancel_delayed_work_sync(&SB_JOURNAL(sb)->j_work);
 
--- a/fs/reiserfs/reiserfs.h
+++ b/fs/reiserfs/reiserfs.h
@@ -2948,6 +2948,7 @@ int reiserfs_allocate_list_bitmaps(struc
 				   struct reiserfs_list_bitmap *, unsigned int);
 
 void reiserfs_schedule_old_flush(struct super_block *s);
+void reiserfs_cancel_old_flush(struct super_block *s);
 void add_save_link(struct reiserfs_transaction_handle *th,
 		   struct inode *inode, int truncate);
 int remove_save_link(struct inode *inode, int truncate);
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -90,7 +90,9 @@ static void flush_old_commits(struct wor
 	s = sbi->s_journal->j_work_sb;
 
 	spin_lock(&sbi->old_work_lock);
-	sbi->work_queued = 0;
+	/* Avoid clobbering the cancel state... */
+	if (sbi->work_queued == 1)
+		sbi->work_queued = 0;
 	spin_unlock(&sbi->old_work_lock);
 
 	reiserfs_sync_fs(s, 1);
@@ -117,21 +119,22 @@ void reiserfs_schedule_old_flush(struct
 	spin_unlock(&sbi->old_work_lock);
 }
 
-static void cancel_old_flush(struct super_block *s)
+void reiserfs_cancel_old_flush(struct super_block *s)
 {
 	struct reiserfs_sb_info *sbi = REISERFS_SB(s);
 
-	cancel_delayed_work_sync(&REISERFS_SB(s)->old_work);
 	spin_lock(&sbi->old_work_lock);
-	sbi->work_queued = 0;
+	/* Make sure no new flushes will be queued */
+	sbi->work_queued = 2;
 	spin_unlock(&sbi->old_work_lock);
+	cancel_delayed_work_sync(&REISERFS_SB(s)->old_work);
 }
 
 static int reiserfs_freeze(struct super_block *s)
 {
 	struct reiserfs_transaction_handle th;
 
-	cancel_old_flush(s);
+	reiserfs_cancel_old_flush(s);
 
 	reiserfs_write_lock(s);
 	if (!(s->s_flags & MS_RDONLY)) {
@@ -152,7 +155,13 @@ static int reiserfs_freeze(struct super_
 
 static int reiserfs_unfreeze(struct super_block *s)
 {
+	struct reiserfs_sb_info *sbi = REISERFS_SB(s);
+
 	reiserfs_allow_writes(s);
+	spin_lock(&sbi->old_work_lock);
+	/* Allow old_work to run again */
+	sbi->work_queued = 0;
+	spin_unlock(&sbi->old_work_lock);
 	return 0;
 }
 
@@ -2194,7 +2203,7 @@ error_unlocked:
 	if (sbi->commit_wq)
 		destroy_workqueue(sbi->commit_wq);
 
-	cancel_delayed_work_sync(&REISERFS_SB(s)->old_work);
+	reiserfs_cancel_old_flush(s);
 
 	reiserfs_free_bitmap_cache(s);
 	if (SB_BUFFER_WITH_SB(s))