From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:41050 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732701AbfHBP1k (ORCPT ); Fri, 2 Aug 2019 11:27:40 -0400 Date: Fri, 2 Aug 2019 11:27:37 -0400 From: Brian Foster Subject: Re: [PATCH 02/24] shrinkers: use will_defer for GFP_NOFS sensitive shrinkers Message-ID: <20190802152737.GB60893@bfoster> References: <20190801021752.4986-1-david@fromorbit.com> <20190801021752.4986-3-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190801021752.4986-3-david@fromorbit.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dave Chinner Cc: linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org On Thu, Aug 01, 2019 at 12:17:30PM +1000, Dave Chinner wrote: > From: Dave Chinner > > For shrinkers that currently avoid scanning when called under > GFP_NOFS contexts, conver them to use the new ->will_defer flag > rather than checking and returning errors during scans. > > This makes it very clear that these shrinkers are not doing any work > because of the context limitations, not because there is no work > that can be done. > > Signed-off-by: Dave Chinner > --- > drivers/staging/android/ashmem.c | 8 ++++---- > fs/gfs2/glock.c | 5 +++-- > fs/gfs2/quota.c | 6 +++--- > fs/nfs/dir.c | 6 +++--- > fs/super.c | 6 +++--- > fs/xfs/xfs_buf.c | 4 ++++ > fs/xfs/xfs_qm.c | 11 ++++++++--- > net/sunrpc/auth.c | 5 ++--- > 8 files changed, 30 insertions(+), 21 deletions(-) > ... > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c > index ca0849043f54..6e0f76532535 100644 > --- a/fs/xfs/xfs_buf.c > +++ b/fs/xfs/xfs_buf.c > @@ -1680,6 +1680,10 @@ xfs_buftarg_shrink_count( > { > struct xfs_buftarg *btp = container_of(shrink, > struct xfs_buftarg, bt_shrinker); > + > + if (!(sc->gfp_mask & __GFP_FS)) > + sc->will_defer = true; > + > return list_lru_shrink_count(&btp->bt_lru, sc); > } This hunk looks like a behavior change / bug fix..? The rest of the patch converts existing logic to bail out of scans to use the new count time defer mechanism. The change is probably fine, but I think we should have a separate patch to introduce this behavior in the first place (which BTW could be sent as a standalone patch and just picked up by this on eventual rebase). Brian > > diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c > index 5e7a37f0cf84..13c842e8f13b 100644 > --- a/fs/xfs/xfs_qm.c > +++ b/fs/xfs/xfs_qm.c > @@ -502,9 +502,6 @@ xfs_qm_shrink_scan( > unsigned long freed; > int error; > > - if ((sc->gfp_mask & (__GFP_FS|__GFP_DIRECT_RECLAIM)) != (__GFP_FS|__GFP_DIRECT_RECLAIM)) > - return 0; > - > INIT_LIST_HEAD(&isol.buffers); > INIT_LIST_HEAD(&isol.dispose); > > @@ -534,6 +531,14 @@ xfs_qm_shrink_count( > struct xfs_quotainfo *qi = container_of(shrink, > struct xfs_quotainfo, qi_shrinker); > > + /* > + * __GFP_DIRECT_RECLAIM is used here to avoid blocking kswapd > + */ > + if ((sc->gfp_mask & (__GFP_FS|__GFP_DIRECT_RECLAIM)) != > + (__GFP_FS|__GFP_DIRECT_RECLAIM)) { > + sc->will_defer = true; > + } > + > return list_lru_shrink_count(&qi->qi_lru, sc); > } > > diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c > index cdb05b48de44..6babcbac4a00 100644 > --- a/net/sunrpc/auth.c > +++ b/net/sunrpc/auth.c > @@ -527,9 +527,6 @@ static unsigned long > rpcauth_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) > > { > - if ((sc->gfp_mask & GFP_KERNEL) != GFP_KERNEL) > - return SHRINK_STOP; > - > /* nothing left, don't come back */ > if (list_empty(&cred_unused)) > return SHRINK_STOP; > @@ -541,6 +538,8 @@ static unsigned long > rpcauth_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc) > > { > + if ((sc->gfp_mask & GFP_KERNEL) != GFP_KERNEL) > + sc->will_defer = true; > return number_cred_unused * sysctl_vfs_cache_pressure / 100; > } > > -- > 2.22.0 >