From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Tino Lehnig <tino.lehnig@contabo.de>,
stable@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH 1/2] zram: remove BD_CAP_SYNCHRONOUS_IO with writeback feature
Date: Fri, 3 Aug 2018 11:52:30 +0900 [thread overview]
Message-ID: <20180803025230.GA502@jagdpanzerIV> (raw)
In-Reply-To: <20180803023929.GA7500@jagdpanzerIV>
On (08/03/18 11:39), Sergey Senozhatsky wrote:
> [..]
>
> > A reader looking at this would wonder "why the heck are we doing that".
> > Adding a code comment would help them.
>
> The interesting thing here is that include/linux/backing-dev.h
> BDI_CAP_SYNCHRONOUS_IO comment says
>
> "Device is so fast that asynchronous IO would be inefficient."
>
> Which is not the reason why BDI_CAP_SYNCHRONOUS_IO is used by ZRAM.
> Probably, the comment needs to be updated as well.
>
> Both SWP_SYNCHRONOUS_IO and BDI_CAP_SYNCHRONOUS_IO tend to pivot
> "efficiency" [looking at the comments], but in ZRAM's case the whole
> reason to use SYNC IO is a race condition and user-after-free that
^ASYNC IO
-ss
next prev parent reply other threads:[~2018-08-03 2:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-02 5:11 [PATCH 1/2] zram: remove BD_CAP_SYNCHRONOUS_IO with writeback feature Minchan Kim
2018-08-02 21:13 ` Andrew Morton
2018-08-03 2:39 ` Sergey Senozhatsky
2018-08-03 2:52 ` Sergey Senozhatsky [this message]
2018-08-03 3:00 ` Minchan Kim
2018-08-03 4:13 ` Sergey Senozhatsky
2018-08-03 4:51 ` Minchan Kim
2018-08-03 5:23 ` Sergey Senozhatsky
2018-08-03 5:45 ` Sergey Senozhatsky
2018-08-03 2:51 ` Minchan Kim
2018-08-03 23:28 ` Andrew Morton
2018-08-05 23:15 ` Minchan Kim
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