[PATCH AUTOSEL for 4.9 110/219] reiserfs: Make cancel_old_flush() reliable

Sasha Levin
2018-03-03T22:34:37Z

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>
---
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 bc2dde2423c2..76108185854e 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -1959,7 +1959,7 @@ 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 e101d70d2327..dec6c93044fa 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;
}

@@ -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))
--
2.14.1