From: Michal Hocko <mhocko@kernel.org>
To: NeilBrown <neilb@suse.de>
Cc: Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@infradead.org>,
Trond Myklebust <trondmy@hammerspace.com>,
"Anna.Schumaker@Netapp.com" <Anna.Schumaker@netapp.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-nfs@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2 - v2] MM: Discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead.
Date: Mon, 6 Apr 2020 09:41:19 +0200 [thread overview]
Message-ID: <20200406074119.GG19426@dhcp22.suse.cz> (raw)
In-Reply-To: <87pnclwjvr.fsf@notabene.neil.brown.name>
On Mon 06-04-20 10:14:16, Neil Brown wrote:
> On Fri, Apr 03 2020, Michal Hocko wrote:
>
> > On Fri 03-04-20 11:42:20, Jan Kara wrote:
> > [...]
> >> > diff --git a/mm/vmstat.c b/mm/vmstat.c
> >> > index 78d53378db99..d1291537bbb9 100644
> >> > --- a/mm/vmstat.c
> >> > +++ b/mm/vmstat.c
> >> > @@ -1162,7 +1162,6 @@ const char * const vmstat_text[] = {
> >> > "nr_file_hugepages",
> >> > "nr_file_pmdmapped",
> >> > "nr_anon_transparent_hugepages",
> >> > - "nr_unstable",
> >> > "nr_vmscan_write",
> >> > "nr_vmscan_immediate_reclaim",
> >> > "nr_dirtied",
> >>
> >> This is probably the most tricky to deal with given how /proc/vmstat is
> >> formatted. OTOH for this file there's good chance we'd get away with just
> >> deleting nr_unstable line because there are entries added to it in the
> >> middle (e.g. in 60fbf0ab5da1 last September) and nobody complained yet.
> >>
> >> What do mm people think? How were changes to vmstat counters handled in the
> >> past?
> >
> > Adding new counters in the middle seems to be generally OK. I would be
> > more worried about removing counters though. So if we can simply print a
> > phone value at the very end then this should be a reasonable workaround.
>
> At the very end?
> Do you mean not have "nr_unstable 0" appear at all, but having "dummy 0"
> appear at the end just so that the number of lines doesn't decrease?
> Am I misunderstanding?
Sorry for not being clear. I meant semething like
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 78d53378db99..836e3f7a7aff 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1705,8 +1705,16 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
{
(*pos)++;
- if (*pos >= NR_VMSTAT_ITEMS)
+ if (*pos >= NR_VMSTAT_ITEMS) {
+ /*
+ * deprecated counters which are no longer represented
+ * in vmstat arrays. We just lie about them to be always
+ * 0 to not break userspace which might expect them in
+ * int the output.
+ */
+ seq_puts(m, "nr_unstable 0")
return NULL;
+ }
return (unsigned long *)m->private + *pos;
}
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-04-06 7:41 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 3:25 [PATCH/RFC] MM: fix writeback for NFS NeilBrown
2020-04-01 23:52 ` Writeback fixes " NeilBrown
2020-04-01 23:53 ` [PATCH 1/2] MM: replace PF_LESS_THROTTLE with PF_LOCAL_THROTTLE NeilBrown
2020-04-01 23:54 ` [PATCH 2/2] Deprecate NR_UNSTABLE_NFS, use NR_WRITEBACK NeilBrown
2020-04-02 15:10 ` Christoph Hellwig
2020-04-02 22:35 ` [PATCH 2/2 - v2] MM: Discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead NeilBrown
2020-04-03 9:42 ` Jan Kara
2020-04-03 11:03 ` Michal Hocko
2020-04-06 0:14 ` NeilBrown
2020-04-06 7:41 ` Michal Hocko [this message]
2020-04-06 23:28 ` NeilBrown
2020-04-07 7:33 ` Michal Hocko
2020-04-02 19:55 ` [PATCH 2/2] Deprecate NR_UNSTABLE_NFS, use NR_WRITEBACK Jan Kara
2020-04-02 16:35 ` [PATCH 1/2] MM: replace PF_LESS_THROTTLE with PF_LOCAL_THROTTLE Jan Kara
2020-04-03 15:15 ` Michal Hocko
2020-04-03 21:40 ` NeilBrown
2020-04-06 7:44 ` Michal Hocko
2020-04-06 9:36 ` Jan Kara
2020-04-06 10:57 ` Michal Hocko
2020-04-06 11:58 ` NeilBrown
2020-04-02 4:26 ` Hillf Danton
2020-04-02 4:57 ` NeilBrown
2020-04-06 3:58 ` Hillf Danton
2020-04-06 23:42 ` Writeback fixes for NFS - V2 NeilBrown
2020-04-06 23:43 ` [PATCH 1/2] MM: replace PF_LESS_THROTTLE with PF_LOCAL_THROTTLE NeilBrown
2020-04-07 16:10 ` Chuck Lever
2020-04-16 0:29 ` Writeback fixes for NFS - V3 NeilBrown
2020-04-16 0:30 ` [PATCH 1/2 V3] MM: replace PF_LESS_THROTTLE with PF_LOCAL_THROTTLE NeilBrown
2020-04-16 6:54 ` Christoph Hellwig
2020-04-16 15:19 ` Jan Kara
2020-04-21 2:22 ` NeilBrown
2020-04-22 12:46 ` Jan Kara
2020-05-13 7:16 ` NeilBrown
2020-05-13 7:17 ` [PATCH 1/2 V4] " NeilBrown
2020-05-15 11:10 ` Jan Kara
2020-06-01 0:46 ` Writeback fixes for NFS NeilBrown
2020-06-01 0:48 ` [PATCH 1/2] MM: replace PF_LESS_THROTTLE with PF_LOCAL_THROTTLE NeilBrown
2020-06-01 0:49 ` [PATCH 2/2] MM: Discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead NeilBrown
2020-05-13 7:18 ` [PATCH 2/2 V4] " NeilBrown
2020-05-15 9:59 ` Jan Kara
2020-04-16 0:31 ` [PATCH 2/2 V3] " NeilBrown
2020-04-16 6:56 ` Christoph Hellwig
2020-04-16 15:24 ` Jan Kara
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200406074119.GG19426@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=Anna.Schumaker@netapp.com \
--cc=akpm@linux-foundation.org \
--cc=hch@infradead.org \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nfs@vger.kernel.org \
--cc=neilb@suse.de \
--cc=trondmy@hammerspace.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).