From: Al Viro <viro@zeniv.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Michael Kerrisk <mtk.manpages@gmail.com>,
shuah@kernel.org, Linux API <linux-api@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-man <linux-man@vger.kernel.org>,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 1/3] readfile: implement readfile syscall
Date: Sat, 4 Jul 2020 21:12:06 +0100 [thread overview]
Message-ID: <20200704201206.GD2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAJfpegusi8BjWFzEi05926d4RsEQvPnRW-w7My=ibBHQ8NgCuw@mail.gmail.com>
On Sat, Jul 04, 2020 at 09:41:09PM +0200, Miklos Szeredi wrote:
> And "If the size of file is smaller than the value provided in count
> then the whole file will be copied into buf", which is simply a lie;
> for example seq_file will happily return a smaller-than-PAGE_SIZE
> chunk if at least one record fits in there. You'll have a very hard
> time explaining that in the man page. So I think there are two
> possible ways forward:
>
> 1) just leave the first explanation (it's an open + read + close
> equivalent) and leave out the rest
>
> 2) add a loop around the vfs_read() in the code.
3) don't bother with the entire thing, until somebody manages to demonstrate
a setup where it does make a real difference (compared to than the obvious
sequence of syscalls, that is). At which point we'll need to figure out
what's going on and deal with the underlying problem of that setup.
next prev parent reply other threads:[~2020-07-04 20:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-04 14:02 [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster Greg Kroah-Hartman
2020-07-04 14:02 ` [PATCH 1/3] readfile: implement readfile syscall Greg Kroah-Hartman
2020-07-04 18:35 ` Geert Uytterhoeven
2020-07-04 19:14 ` Matthew Wilcox
2020-07-04 19:41 ` Miklos Szeredi
2020-07-04 20:12 ` Al Viro [this message]
2020-07-04 20:16 ` Al Viro
2020-07-04 14:02 ` [PATCH 2/3] arch: wire up the " Greg Kroah-Hartman
2020-07-04 18:36 ` Geert Uytterhoeven
2020-07-04 14:02 ` [PATCH 3/3] selftests: add readfile(2) selftests Greg Kroah-Hartman
2020-07-04 18:38 ` Geert Uytterhoeven
2020-07-05 6:55 ` Greg Kroah-Hartman
2020-07-05 11:24 ` Geert Uytterhoeven
2020-07-05 11:36 ` Greg Kroah-Hartman
2020-07-05 1:41 ` Heinrich Schuchardt
2020-07-05 7:34 ` Greg Kroah-Hartman
2020-07-05 9:46 ` Heinrich Schuchardt
2020-07-04 14:02 ` [PATCH] readfile.2: new page describing readfile(2) Greg Kroah-Hartman
2020-07-05 2:54 ` Heinrich Schuchardt
2020-07-04 19:30 ` [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster Al Viro
2020-07-05 11:47 ` Greg Kroah-Hartman
2020-07-06 17:25 ` Dave Martin
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