On Mon, Jul 30, 2018 at 10:53:53AM +0200, Vlastimil Babka wrote:

On 07/26/2018 06:26 PM, Alexey Dobriyan wrote:

quoted

On Wed, Jul 25, 2018 at 08:53:53AM +0200, Vlastimil Babka wrote:

quoted

I moved the reply to this thread since the "added to -mm tree"
notification Alexey replied to in <20180724182908.GD27053@avx2> has
reduced CC list and is not linked to the patch postings.

On 07/24/2018 08:29 PM, Alexey Dobriyan wrote:

quoted

On Mon, Jul 23, 2018 at 04:55:48PM -0700, akpm@linux-foundation.org wrote:

quoted

The patch titled
     Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file
has been added to the -mm tree.  Its filename is
     mm-proc-pid-smaps_rollup-convert-to-single-value-seq_file.patch

quoted

Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file

The /proc/pid/smaps_rollup file is currently implemented via the
m_start/m_next/m_stop seq_file iterators shared with the other maps files,
that iterate over vma's.  However, the rollup file doesn't print anything
for each vma, only accumulate the stats.

What I don't understand why keep seq_ops then and not do all the work in
->show hook.  Currently /proc/*/smaps_rollup is at ~500 bytes so with
minimum 1 page seq buffer, no buffer resizing is possible.

Hmm IIUC seq_file also provides the buffer and handles feeding the data
from there to the user process, which might have called read() with a smaller
buffer than that. So I would rather not avoid the seq_file infrastructure.
Or you're saying it could be converted to single_open()? Maybe, with more work.

Prefereably yes.

OK here it is. Sending as a new patch instead of delta, as that's easier
to review - the delta is significant. Line stats wise it's the same.
Again a bit less boilerplate thans to no special seq_ops, a bit more
copy/paste in the open and release functions. But I guess it's better
overall.

----8>----
From c6a2eaf3bb3546509d6b7c42f8bcc56cd7e92f90 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <redacted>
Date: Wed, 18 Jul 2018 13:14:30 +0200
Subject: [PATCH] mm: proc/pid/smaps_rollup: convert to single value seq_file

Reviewed-by: Alexey Dobriyan <redacted>