Messages in this thread | | | Subject | Re: __make_request() bug and a fix variant | From | Arjan van de Ven <> | Date | Sat, 20 Sep 2003 17:47:34 +0200 |
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On Sat, 2003-09-20 at 17:36, Andrew Zabolotny wrote: > On Sat, 20 Sep 2003 13:37:37 +0200 > Jens Axboe <axboe@suse.de> wrote: > > > I dunno if you were the one posting this issue here some months ago? > No, it wasn't me :-) > > > Show me a regular kernel path that passes invalid b_reqnext to > > __make_request? That would be a bug, indeed, but I've never heard of > > such a bug. Most likely it's a bug in your driver, not initialising > > b_reqnext. > I have been calling bread() which was causing me troubles. bread does > not accept a buffer_head from outside, it gets a new one and returns it. > So I don't have any control over b_reqnext field - the bug happens > inside bread() between these lines: > > bh = getblk(dev, block, size); > /* here bh_reqnext is already junk. In fact, I partially solved this > problem by making my own clone of bread() and setting b_reqnext > to NULL right here. But unfortunately, there is no guarantee we'll > fix all invalid buffer_heads - maybe some remain in the pool and > will be returned to other innocent drivers requesting them. */ > if (buffer_uptodate(bh)) > return bh; > /* and now ll_rw_block will try to merge the bh with those already in > the queue, and if it will take the ELEVATOR_NO_MERGE path, bh_reqnext > will still remain junk. */ > ll_rw_block(READ, 1, &bh); > > > You can see the initialisor for buffer_heads is > > init_buffer_head, which memsets the entire buffer_head. When a > > buffer_head is detached from the request list, b_reqnext is cleared > > too. > Ah, so I was correct that __make_request expects b_reqnext to be already > set to NULL. In this case the bug should be somewhere else - in some > code that returns buffer_head's back to the pool of buffers. > > Interesting that right before the driver crashes in bread() I call > grok_partitions. I think the bug is somewhere there. I will do a new > debug session at Monday (the code that breaks is at work), so I will > post new details if I find any.
it may help if you post the url to your full driver code here; others may help you debugging.... [unhandled content-type:application/pgp-signature] | |