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From: "Chen, Tim C" <tim.c.chen@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Yang Shi <yang.shi@linux.alibaba.com>
Cc: "Huang, Ying" <ying.huang@intel.com>,
	"minchan@kernel.org" <minchan@kernel.org>,
	"daniel.m.jordan@oracle.com" <daniel.m.jordan@oracle.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [v5 PATCH 1/2] mm: swap: check if swap backing device is congested or not
Date: Thu, 10 Jan 2019 23:40:01 +0000	[thread overview]
Message-ID: <045D8A5597B93E4EBEDDCBF1FC15F5097E16F8E2@fmsmsx121.amr.corp.intel.com> (raw)
In-Reply-To: <20190110153147.1baf4c88bf0dd3b8a78aad08@linux-foundation.org>

> >
> > +	if (si->flags & (SWP_BLKDEV | SWP_FS)) {
> 
> I re-read your discussion with Tim and I must say the reasoning behind this
> test remain foggy.

I was worried that the dereference

inode = si->swap_file->f_mapping->host;

is not always safe for corner cases.

So the test makes sure that the dereference is valid.

> 
> What goes wrong if we just remove it?

If the dereference to get inode is always safe, we can remove it.


Thanks.

Tim

  reply	other threads:[~2019-01-10 23:40 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-03 19:27 Yang Shi
2019-01-03 19:27 ` [v5 PATCH 2/2] mm: swap: add comment for swap_vma_readahead Yang Shi
2019-01-04  2:25   ` Huang, Ying
2019-01-04  2:25     ` Huang, Ying
2019-01-10 20:49 ` [v5 PATCH 1/2] mm: swap: check if swap backing device is congested or not Yang Shi
2019-01-10 23:20 ` Andrew Morton
2019-01-10 23:31 ` Andrew Morton
2019-01-10 23:40   ` Chen, Tim C [this message]
2019-01-11  0:56   ` Yang Shi

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