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    Subject[PATCH 3.14 26/44] ocfs2: fix BUG in ocfs2_downconvert_thread_do_work()
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Joseph Qi <joseph.qi@huawei.com>

    commit 209f7512d007980fd111a74a064d70a3656079cf upstream.

    The "BUG_ON(list_empty(&osb->blocked_lock_list))" in
    ocfs2_downconvert_thread_do_work can be triggered in the following case:

    ocfs2dc has firstly saved osb->blocked_lock_count to local varibale
    processed, and then processes the dentry lockres. During the dentry
    put, it calls iput and then deletes rw, inode and open lockres from
    blocked list in ocfs2_mark_lockres_freeing. And this causes the
    variable `processed' to not reflect the number of blocked lockres to be
    processed, which triggers the BUG.

    Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
    Cc: Mark Fasheh <mfasheh@suse.com>
    Cc: Joel Becker <jlbec@evilplan.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ocfs2/dlmglue.c | 10 +++++++---
    1 file changed, 7 insertions(+), 3 deletions(-)

    --- a/fs/ocfs2/dlmglue.c
    +++ b/fs/ocfs2/dlmglue.c
    @@ -3973,9 +3973,13 @@ static void ocfs2_downconvert_thread_do_
    osb->dc_work_sequence = osb->dc_wake_sequence;

    processed = osb->blocked_lock_count;
    - while (processed) {
    - BUG_ON(list_empty(&osb->blocked_lock_list));
    -
    + /*
    + * blocked lock processing in this loop might call iput which can
    + * remove items off osb->blocked_lock_list. Downconvert up to
    + * 'processed' number of locks, but stop short if we had some
    + * removed in ocfs2_mark_lockres_freeing when downconverting.
    + */
    + while (processed && !list_empty(&osb->blocked_lock_list)) {
    lockres = list_entry(osb->blocked_lock_list.next,
    struct ocfs2_lock_res, l_blocked_list);
    list_del_init(&lockres->l_blocked_list);



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