linux-kernel - Re: [PATCH 8/8] net: sunrpc: Replace CURRENT_TIME by current_fs

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Message-ID: <CABeXuvq6Fxcj15Zo9F7tPUN+-Jw7nOPcH8AHKP29Q+6R4mqmRQ@mail.gmail.com>
Date:	Mon, 22 Feb 2016 21:17:29 +0530
From:	Deepa Dinamani <deepa.kernel@...il.com>
To:	Trond Myklebust <trond.myklebust@...marydata.com>
Cc:	Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
	y2038@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Jeff Layton <jlayton@...chiereds.net>,
	Anna Schumaker <anna.schumaker@...app.com>,
	"David S. Miller" <davem@...emloft.net>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Network Devel Mailing List <netdev@...r.kernel.org>
Subject: Re: [PATCH 8/8] net: sunrpc: Replace CURRENT_TIME by current_fs_time()

On Mon, Feb 22, 2016 at 9:04 PM, Trond Myklebust
<trond.myklebust@...marydata.com> wrote:
> On Mon, Feb 22, 2016 at 10:17 AM, Deepa Dinamani <deepa.kernel@...il.com> wrote:
>>
>> CURRENT_TIME macro is not appropriate for filesystems as it
>> doesn't use the right granularity for filesystem timestamps.
>> Use current_fs_time() instead.
>>
>> Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
>> Cc: "J. Bruce Fields" <bfields@...ldses.org>
>> Cc: Jeff Layton <jlayton@...chiereds.net>
>> Cc: Trond Myklebust <trond.myklebust@...marydata.com>
>> Cc: Anna Schumaker <anna.schumaker@...app.com>
>> Cc: "David S. Miller" <davem@...emloft.net>
>> Cc: linux-nfs@...r.kernel.org
>> Cc: netdev@...r.kernel.org
>> ---
>>  net/sunrpc/rpc_pipe.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
>> index 31789ef..bab3187 100644
>> --- a/net/sunrpc/rpc_pipe.c
>> +++ b/net/sunrpc/rpc_pipe.c
>> @@ -477,7 +477,9 @@ rpc_get_inode(struct super_block *sb, umode_t mode)
>>                 return NULL;
>>         inode->i_ino = get_next_ino();
>>         inode->i_mode = mode;
>> -       inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
>> +       inode->i_atime = current_fs_time(sb);
>> +       inode->i_mtime = inode->i_atime;
>> +       inode->i_ctime = inode->i_atime;
>>         switch (mode & S_IFMT) {
>>         case S_IFDIR:
>>                 inode->i_fop = &simple_dir_operations;
>
> Why would we care? This is a pseudo-fs. There is no expectation w.r.t.
> timestamp accuracy or resolution.

CURRENT_TIME is not y2038 safe.
We are switching all vfs timestamps to use 64 bit time.
And, deleting all references to CURRENT_TIME.
So CURRENT_TIME users will be replaced by either ktime_get_* apis
or current_fs_time_* apis.

There is going to be another series (based on
https://lkml.org/lkml/2016/2/12/76)
which switches vfs time to 64 bit.

This means [a,c,m] times in struct inode, struct attr and struct kstat
will be changed to use timespec64.

Even though this is a psuedo-fs, we choose to use filesystem apis
rather than ktime_get_* apis as current_fs_time_* apis will switch time
data types together with vfs.

-Deepa