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    Subject[PATCH 3.2 133/152] ocfs2/dlm: fix race between convert and migration
    3.2.84-rc1 review patch.  If anyone has any objections, please let me know.

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

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

    commit e6f0c6e6170fec175fe676495f29029aecdf486c upstream.

    Commit ac7cf246dfdb ("ocfs2/dlm: fix race between convert and recovery")
    checks if lockres master has changed to identify whether new master has
    finished recovery or not. This will introduce a race that right after
    old master does umount ( means master will change), a new convert
    request comes.

    In this case, it will reset lockres state to DLM_RECOVERING and then
    retry convert, and then fail with lockres->l_action being set to
    OCFS2_AST_INVALID, which will cause inconsistent lock level between
    ocfs2 and dlm, and then finally BUG.

    Since dlm recovery will clear lock->convert_pending in
    dlm_move_lockres_to_recovery_list, we can use it to correctly identify
    the race case between convert and recovery. So fix it.

    Fixes: ac7cf246dfdb ("ocfs2/dlm: fix race between convert and recovery")
    Link: http://lkml.kernel.org/r/57CE1569.8010704@huawei.com
    Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
    Signed-off-by: Jun Piao <piaojun@huawei.com>
    Cc: Mark Fasheh <mfasheh@suse.de>
    Cc: Joel Becker <jlbec@evilplan.org>
    Cc: Junxiao Bi <junxiao.bi@oracle.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    fs/ocfs2/dlm/dlmconvert.c | 12 ++++++------
    1 file changed, 6 insertions(+), 6 deletions(-)

    --- a/fs/ocfs2/dlm/dlmconvert.c
    +++ b/fs/ocfs2/dlm/dlmconvert.c
    @@ -265,7 +265,6 @@ enum dlm_status dlmconvert_remote(struct
    struct dlm_lock *lock, int flags, int type)
    {
    enum dlm_status status;
    - u8 old_owner = res->owner;

    mlog(0, "type=%d, convert_type=%d, busy=%d\n", lock->ml.type,
    lock->ml.convert_type, res->state & DLM_LOCK_RES_IN_PROGRESS);
    @@ -332,7 +331,6 @@ enum dlm_status dlmconvert_remote(struct

    spin_lock(&res->spinlock);
    res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
    - lock->convert_pending = 0;
    /* if it failed, move it back to granted queue.
    * if master returns DLM_NORMAL and then down before sending ast,
    * it may have already been moved to granted queue, reset to
    @@ -341,12 +339,14 @@ enum dlm_status dlmconvert_remote(struct
    if (status != DLM_NOTQUEUED)
    dlm_error(status);
    dlm_revert_pending_convert(res, lock);
    - } else if ((res->state & DLM_LOCK_RES_RECOVERING) ||
    - (old_owner != res->owner)) {
    - mlog(0, "res %.*s is in recovering or has been recovered.\n",
    - res->lockname.len, res->lockname.name);
    + } else if (!lock->convert_pending) {
    + mlog(0, "%s: res %.*s, owner died and lock has been moved back "
    + "to granted list, retry convert.\n",
    + dlm->name, res->lockname.len, res->lockname.name);
    status = DLM_RECOVERING;
    }
    +
    + lock->convert_pending = 0;
    bail:
    spin_unlock(&res->spinlock);

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