From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: mgorman@techsingularity.net, tytso@mit.edu,
adilger.kernel@dilger.ca, dchinner@redhat.com,
akpm@linux-foundation.org, linux-ext4@vger.kernel.org,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] fs: xfs: use BUG_ON if writepage call comes from direct reclaim
Date: Tue, 3 Jul 2018 10:19:20 -0700 [thread overview]
Message-ID: <20180703171920.GC5711@magnolia> (raw)
In-Reply-To: <1530591079-33813-2-git-send-email-yang.shi@linux.alibaba.com>
On Tue, Jul 03, 2018 at 12:11:19PM +0800, Yang Shi wrote:
> direct reclaim doesn't write out filesystem page, only kswapd could do
> this. So, if it is called from direct relaim, it is definitely a bug.
>
> And, Mel Gorman mentioned "Ultimately, this will be a BUG_ON." in commit
> 94054fa3fca1fd78db02cb3d68d5627120f0a1d4 ("xfs: warn if direct reclaim
> tries to writeback pages"),
>
> It has been many years since that commit, so it should be safe to
> elevate WARN_ON to BUG_ON now.
>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Darrick J. Wong <darrick.wong@oracle.com>
> Cc: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> ---
> fs/xfs/xfs_aops.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 8eb3ba3..7efc2d2 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1080,11 +1080,9 @@ static inline int xfs_bio_add_buffer(struct bio *bio, struct buffer_head *bh)
> * allow reclaim from kswapd as the stack usage there is relatively low.
> *
> * This should never happen except in the case of a VM regression so
> - * warn about it.
> + * BUG about it.
> */
> - if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
> - PF_MEMALLOC))
> - goto redirty;
> + BUG_ON((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC);
Ugh, please do not increase the BUG() factor. Even if this happens due
to a regression it's /much/ easier to debug if we don't halt the system.
(IOWs, I decline to take this patch.)
--D
>
> /*
> * Given that we do not allow direct reclaim to call us, we should
> --
> 1.8.3.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2018-07-03 17:19 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-03 4:11 [PATCH 1/2] fs: ext4: use BUG_ON if writepage call comes from direct reclaim Yang Shi
2018-07-03 4:11 ` [PATCH 2/2] fs: xfs: " Yang Shi
2018-07-03 4:37 ` Dave Chinner
2018-07-03 17:19 ` Darrick J. Wong [this message]
2018-07-03 10:39 ` [PATCH 1/2] fs: ext4: " Theodore Y. Ts'o
2018-07-03 17:05 ` Yang Shi
2018-07-03 23:10 ` Yang Shi
2018-07-03 23:43 ` Theodore Y. Ts'o
2018-07-04 14:03 ` Michal Hocko
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