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    Subject[PATCH AUTOSEL for 4.4 053/115] reiserfs: Make cancel_old_flush() reliable
    Date
    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 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
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