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Date: Fri, 29 Sep 2017 02:17:32 +0200 From: Jens Axboe <axboe@...nel.dk> To: Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz> Subject: Re: [PATCH 10/12] writeback: only allow one inflight and pending full flush On 09/28/2017 11:44 PM, Linus Torvalds wrote: > On Thu, Sep 28, 2017 at 2:41 PM, Andrew Morton > <akpm@...ux-foundation.org> wrote: >> >> test_and_set_bit()? > > If there aren't any atomicity concerns (either because of higher-level > locking, or because racing and having two people set the bit is fine), > it can be better to do them separately if the test_bit() is the common > case and you can avoid dirtying a cacheline that way. > > But yeah, if that is the case, it might be worth documenting, because > test_and_set_bit() is the more obviously appropriate "there can be > only one" model. It is documented though, but maybe not well enough... I've actually had to document/explain it enough times now, that it might be worth making a general construct. Though it has to be used carefully, so perhaps it's better contained as separate use cases. -- Jens Axboe
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