Messages in this thread | | | Date | Fri, 2 May 2003 10:16:34 +0200 | From | Jens Axboe <> | Subject | Re: Re-drive buffer head more than once |
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On Thu, May 01 2003, Zhihui Zhang wrote: > Hi, > > Is it legal to call general_make_request() more than once on the same bh? > What will happen if a previous request is still in the queue, or just > initiated but not finished yet? If I call general_make_request() on the > same buffer 10 times, does it mean the same buffer will *always* be > written 10 times on the disk?
It's not legal to call generic_make_request() on a buffer_head, if you have not acquired the BH_Lock first. The buffer_head will be unlocked on IO completion, so that basically tells you that you cannot issue more than _one_ generic_make_request() on a buffer_head.
If you fail to comply with that, then you will basically corrupt the existing request in the queue where the buffer is attached. You _must_ do a lock_buffer() before calling generic_make_request.
-- Jens Axboe
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