From: Jan Kara <jack@suse.cz>
To: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com
Subject: Re: [block/for-next] writeback: don't access page->mapping directly in track_foreign_dirty TP
Date: Mon, 2 Sep 2019 10:56:28 +0200 [thread overview]
Message-ID: <20190902085628.GC14207@quack2.suse.cz> (raw)
In-Reply-To: <20190830233954.GC2263813@devbig004.ftw2.facebook.com>
On Fri 30-08-19 16:39:54, Tejun Heo wrote:
> page->mapping may encode different values in it and page_mapping()
> should always be used to access the mapping pointer.
> track_foreign_dirty tracepoint was incorrectly accessing page->mapping
> directly. Use page_mapping() instead. Also, add NULL checks while at
> it.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reported-by: Jan Kara <jack@suse.cz>
> Fixes: 3a8e9ac89e6a ("writeback: add tracepoints for cgroup foreign writebacks")
I can see Jens already picked this up so this is just informative: The patch
now looks good to me.
Honza
> ---
> include/trace/events/writeback.h | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
> index 3dc9fb9e7c78..3a27335fce2c 100644
> --- a/include/trace/events/writeback.h
> +++ b/include/trace/events/writeback.h
> @@ -251,9 +251,12 @@ TRACE_EVENT(track_foreign_dirty,
> ),
>
> TP_fast_assign(
> + struct address_space *mapping = page_mapping(page);
> + struct inode *inode = mapping ? mapping->host : NULL;
> +
> strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
> __entry->bdi_id = wb->bdi->id;
> - __entry->ino = page->mapping->host->i_ino;
> + __entry->ino = inode ? inode->i_ino : 0;
> __entry->memcg_id = wb->memcg_css->id;
> __entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
> __entry->page_cgroup_ino = page->mem_cgroup->css.cgroup->kn->id.ino;
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2019-09-02 9:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 23:39 [block/for-next] writeback: don't access page->mapping directly in track_foreign_dirty TP Tejun Heo
2019-08-31 1:54 ` Jens Axboe
2019-09-02 8:56 ` Jan Kara [this message]
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