linux-kernel - [PATCH AUTOSEL for 4.4 053/115] reiserfs: Make cancel_old

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Date:   Sat, 3 Mar 2018 22:31:19 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Jan Kara <jack@...e.cz>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.4 053/115] reiserfs: Make cancel_old_flush()
 reliable

From: Jan Kara <jack@...e.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@...e.cz>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 fs/reiserfs/journal.c  |  2 +-
 fs/reiserfs/reiserfs.h |  1 +
 fs/reiserfs/super.c    | 21 +++++++++++++++------
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index 9d6486d416a3..a72097b625ef 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -1961,7 +1961,7 @@ static int do_journal_release(struct reiserfs_transaction_handle *th,
 	 * 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);
 
diff --git a/fs/reiserfs/reiserfs.h b/fs/reiserfs/reiserfs.h
index 5dcf3ab83886..6ca00471afbf 100644
--- a/fs/reiserfs/reiserfs.h
+++ b/fs/reiserfs/reiserfs.h
@@ -2948,6 +2948,7 @@ int reiserfs_allocate_list_bitmaps(struct super_block *s,
 				   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);
diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index f9f3be50081a..ee095246da4e 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -90,7 +90,9 @@ static void flush_old_commits(struct work_struct *work)
 	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 super_block *s)
 	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_block *s)
 
 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;
 }
 
@@ -2187,7 +2196,7 @@ 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))
-- 
2.14.1