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Date: Tue, 3 Jul 2018 10:19:20 -0700 From: "Darrick J. Wong" <darrick.wong@...cle.com> To: Yang Shi <yang.shi@...ux.alibaba.com> Cc: mgorman@...hsingularity.net, tytso@....edu, adilger.kernel@...ger.ca, dchinner@...hat.com, akpm@...ux-foundation.org, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/2] fs: xfs: use BUG_ON if writepage call comes from direct reclaim 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@...hsingularity.net> > Cc: Darrick J. Wong <darrick.wong@...cle.com> > Cc: Dave Chinner <dchinner@...hat.com> > Signed-off-by: Yang Shi <yang.shi@...ux.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@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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