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Date: Wed, 8 Jul 2015 10:12:49 +0200
From: Jan Kara <jack@suse.cz>
Subject: Re: [PATCH block/for-4.3] writeback: explain why @inode is allowed
 to be NULL for inode_congested()
Message-ID: <20150708081248.GA725@quack.suse.cz>
References: <1432329245-5844-1-git-send-email-tj@kernel.org>
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 <20150630152105.GP7252@quack.suse.cz>
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 <20150703121721.GJ23329@quack.suse.cz>
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To: Tejun Heo <tj@kernel.org>
Cc: Jan Kara <jack@suse.cz>, axboe@kernel.dk, linux-kernel@vger.kernel.org, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, khlebnikov@yandex-team.ru

On Sat 04-07-15 11:12:00, Tejun Heo wrote:
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Suggested-by: Jan Kara <jack@suse.cz>
> ---
> Hello,
> 
> So, something like this.  I'll resend this patch as part of a patch
> series once -rc1 drops.
  Looks good. Thanks!

								Honza

>  fs/fs-writeback.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -700,7 +700,7 @@ void wbc_account_io(struct writeback_con
>  
>  /**
>   * inode_congested - test whether an inode is congested
> - * @inode: inode to test for congestion
> + * @inode: inode to test for congestion (may be NULL)
>   * @cong_bits: mask of WB_[a]sync_congested bits to test
>   *
>   * Tests whether @inode is congested.  @cong_bits is the mask of congestion
> @@ -710,6 +710,9 @@ void wbc_account_io(struct writeback_con
>   * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
>   * associated with @inode is congested; otherwise, the root wb's congestion
>   * state is used.
> + *
> + * @inode is allowed to be NULL as this function is often called on
> + * mapping->host which is NULL for the swapper space.
>   */
>  int inode_congested(struct inode *inode, int cong_bits)
>  {
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

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