From: Jens Axboe <axboe@suse.de>
To: Zhihui Zhang <bf20761@binghamton.edu>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Re-drive buffer head more than once
Date: Fri, 2 May 2003 10:16:34 +0200 [thread overview]
Message-ID: <20030502081633.GC1012@suse.de> (raw)
In-Reply-To: <Pine.SOL.L4.44.0305011246180.28401-100000@bingsun2.cc.binghamton.edu>
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
prev parent reply other threads:[~2003-05-02 8:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-01 16:52 Re-drive buffer head more than once Zhihui Zhang
2003-05-02 8:16 ` Jens Axboe [this message]
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