• Guoqing Jiang's avatar
    md: set MD_CHANGE_PENDING in a atomic region · 85ad1d13
    Guoqing Jiang authored
    Some code waits for a metadata update by:
    
    1. flagging that it is needed (MD_CHANGE_DEVS or MD_CHANGE_CLEAN)
    2. setting MD_CHANGE_PENDING and waking the management thread
    3. waiting for MD_CHANGE_PENDING to be cleared
    
    If the first two are done without locking, the code in md_update_sb()
    which checks if it needs to repeat might test if an update is needed
    before step 1, then clear MD_CHANGE_PENDING after step 2, resulting
    in the wait returning early.
    
    So make sure all places that set MD_CHANGE_PENDING are atomicial, and
    bit_clear_unless (suggested by Neil) is introduced for the purpose.
    
    Cc: Martin Kepplinger <martink@posteo.de>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: Sasha Levin <sasha.levin@oracle.com>
    Cc: <linux-kernel@vger.kernel.org>
    Reviewed-by: 's avatarNeilBrown <neilb@suse.com>
    Signed-off-by: 's avatarGuoqing Jiang <gqjiang@suse.com>
    Signed-off-by: 's avatarShaohua Li <shli@fb.com>
    85ad1d13
bitops.h 6.33 KB