Hi James, On 09/20/11 16:13, James Bottomley wrote: >> James's suggestion was to fix b) by not freeing elevator >> until blk_release_queue() is called: >> https://lkml.org/lkml/2011/8/10/421 >> But it would hit the same issue that there's no guarantee >> of q->queue_lock validity after blk_cleanup_queue(). >> James's other suggestion was to add a callback mechanism >> for driver to free q->queue_lock. > > Actually, there isn't a problem with this patch: Any driver that > expects blk_cleanup_queue to guarantee last use of the lock has to call > it as the last releaser. If it doesn't, it would oops (or would have > oopsed before we started putting the block guards in). 'q->sysfs_lock' seems to protect the queue access via sysfs. Are you sure it never delay the last put? The separation of blk_cleanup_queue() and blk_release_queue() was introduced with the following commit: commit 483f4afc421435b7cfe5e88f74eea0b73a476d75 Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Date: Sat Mar 18 18:34:37 2006 -0500 [PATCH] fix sysfs interaction and lifetime rules handling for queues I added Al to Cc hoping he knows why elevator_exit() was placed in blk_cleanup_queue() from the first time. Other than the above concern, I have no objection to your patch. >> I was trying to fix a) in the following thread: >> https://lkml.org/lkml/2011/8/18/103 >> but haven't gotten response from James so it seems rejected. > > I think I said quite a few times that this would reintroduce the oops I > was trying to fix. Alan seems to think that there are sufficient guards > just to move the blk_cleanup_queue(), but I'd prefer to get > blk_cleanup_queue() working properly like the del method it's supposed > to be. I think you haven't mentioned what oops would be reintroduced. Thanks, -- Jun'ichi Nomura, NEC Corporation -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
