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Date:   Thu, 31 Mar 2022 21:46:21 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Jiasheng Jiang <jiasheng@iscas.ac.cn>
Cc:     hch@infradead.org, rpeterso@redhat.com, agruenba@redhat.com,
        cluster-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [Cluster-devel] [PATCH] gfs2: Add check for mempool_alloc
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On Fri, Apr 01, 2022 at 11:37:55AM +0800, Jiasheng Jiang wrote:
> >> Fixes: e8c92ed76900 ("GFS2: Clean up log write code path")
> >> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
> > 
> > Please explain how it could fail to start with.
> 
> I think that for safety, the cost of redundant and harmless
> check is acceptable.
> Also, checking after allocation is a good program pattern.
> Therefore, it should be better to check it although it is
> hard to fail.

Please take a look at the implemetation and documentation of
mempool_alloc again.  Thewhole point of that function is that it will
not fail for allocations that can sleep.