1. 26 4月, 2007 39 次提交
  2. 25 4月, 2007 1 次提交
    • J
      cfq-iosched: fix alias + front merge bug · 5044eed4
      Jens Axboe 提交于
      There's a really rare and obscure bug in CFQ, that causes a crash in
      cfq_dispatch_insert() due to rq == NULL.  One example of the resulting
      oops is seen here:
      
      	http://lkml.org/lkml/2007/4/15/41
      
      Neil correctly diagnosed the situation for how this can happen: if two
      concurrent requests with the exact same sector number (due to direct IO
      or aliasing between MD and the raw device access), the alias handling
      will add the request to the sortlist, but next_rq remains NULL.
      
      Read the more complete analysis at:
      
      	http://lkml.org/lkml/2007/4/25/57
      
      This looks like it requires md to trigger, even though it should
      potentially be possible to due with O_DIRECT (at least if you edit the
      kernel and doctor some of the unplug calls).
      
      The fix is to move the ->next_rq update to when we add a request to the
      rbtree. Then we remove the possibility for a request to exist in the
      rbtree code, but not have ->next_rq correctly updated.
      Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5044eed4