linux-kernel - Re: [PATCH 01/21] fs: Replace CURRENT_TIME_SEC with current_fs

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Message-ID: <CABeXuvp9MV720nFVHfEOdL0q11xadKezThpsh+5wd1O5KYk6Yg@mail.gmail.com>
Date:	Fri, 10 Jun 2016 22:03:14 -0700
From:	Deepa Dinamani <deepa.kernel@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Bob Copeland <me@...copeland.com>,
	Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	y2038@...ts.linaro.org, Artem Bityutskiy <dedekind1@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	Evgeniy Dushistov <dushistov@...l.ru>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
	David Howells <dhowells@...hat.com>,
	linux-afs@...ts.infradead.org,
	"Tigran A. Aivazian" <tigran@...azian.fsnet.co.uk>,
	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Jan Kara <jack@...e.cz>, Jan Harkes <jaharkes@...cmu.edu>,
	coda@...cmu.edu, linux-karma-devel@...ts.sourceforge.net,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 01/21] fs: Replace CURRENT_TIME_SEC with current_fs_time()

On Fri, Jun 10, 2016 at 3:21 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Wednesday, June 8, 2016 10:04:45 PM CEST Deepa Dinamani wrote:
>> CURRENT_TIME_SEC is not y2038 safe. current_fs_time() will
>> be transitioned to use 64 bit time along with vfs in a
>> separate patch.
>> There is no plan to transistion CURRENT_TIME_SEC to use
>> y2038 safe time interfaces.
>>
>> current_fs_time() will also be extended to use superblock
>> range checking parameters when range checking is introduced.
>>
>> This works because alloc_super() fills in the the s_time_gran
>> in super block to NSEC_PER_SEC.
>>
>> Also note that filesystem specific times like the birthtime,
>> creation time that were using same interfaces to obtain time
>> retain same logistics.
>>
>> Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
>
> one question:
>
> In an earlier version, you had a small optimization to
> use ktime_get_real_seconds() instead of current_kernel_time()
> when the granularity is seconds.
>
> Do you still plan to send that one, or did you decide we don't
> need it?

I was actually planning to use get_seconds() instead of current_kernel_time().
And, transition both along with vfs to y2038 safe apis.
Difference between ktime_get_real_seconds() and current_kernel_time64()
is not much because they both require sequence counter.

It didn't make sense to me to optimize current_fs_time() for seconds
only, and not optimize for 1ns granularity also.
I plan to make changes to the function depending on how we end up
using timespec_trunc()
after the addition of range checking.

Thanks for the guidance on inclusion of reviewers. I'll follow this
approach when I post v2 of the series.

-Deepa