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[73.93.239.127]) by smtp.gmail.com with ESMTPSA id c6sm396906pgl.38.2020.12.02.10.27.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 10:27:52 -0800 (PST) From: Yang Shi To: guro@fb.com, ktkhai@virtuozzo.com, shakeelb@google.com, david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered Date: Wed, 2 Dec 2020 10:27:20 -0800 Message-Id: <20201202182725.265020-5-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201202182725.265020-1-shy828301@gmail.com> References: <20201202182725.265020-1-shy828301@gmail.com> MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. This approach is fine with nr_deferred atthe shrinker level, but the following patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their shrinker->nr_deferred would always be NULL. This would prevent the shrinkers from unregistering correctly. Introduce a new "state" field to indicate if shrinker is registered or not. We could use the highest bit of flags, but it may be a little bit complicated to extract that bit and the flags is accessed frequently by vmscan (every time shrinker is called). So add a new field in "struct shrinker", we may waster a little bit memory, but it should be very few since there should be not too many registered shrinkers on a normal system. Signed-off-by: Yang Shi --- include/linux/shrinker.h | 4 ++++ mm/vmscan.c | 13 +++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 0f80123650e2..0bb5be88e41d 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -35,6 +35,9 @@ struct shrink_control { #define SHRINK_STOP (~0UL) #define SHRINK_EMPTY (~0UL - 1) + +#define SHRINKER_REGISTERED 0x1 + /* * A callback you can register to apply pressure to ageable caches. * @@ -66,6 +69,7 @@ struct shrinker { long batch; /* reclaim batch size, 0 = default */ int seeks; /* seeks to recreate an obj */ unsigned flags; + unsigned state; /* These are for internal use */ struct list_head list; diff --git a/mm/vmscan.c b/mm/vmscan.c index 457ce04eebf2..0d628299e55c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -378,6 +378,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) if (shrinker->flags & SHRINKER_MEMCG_AWARE) idr_replace(&shrinker_idr, shrinker, shrinker->id); #endif + shrinker->state |= SHRINKER_REGISTERED; up_write(&shrinker_rwsem); } @@ -397,13 +398,17 @@ EXPORT_SYMBOL(register_shrinker); */ void unregister_shrinker(struct shrinker *shrinker) { - if (!shrinker->nr_deferred) - return; - if (shrinker->flags & SHRINKER_MEMCG_AWARE) - unregister_memcg_shrinker(shrinker); down_write(&shrinker_rwsem); + if (!shrinker->state) { + up_write(&shrinker_rwsem); + return; + } list_del(&shrinker->list); + shrinker->state &= ~SHRINKER_REGISTERED; up_write(&shrinker_rwsem); + + if (shrinker->flags & SHRINKER_MEMCG_AWARE) + unregister_memcg_shrinker(shrinker); kfree(shrinker->nr_deferred); shrinker->nr_deferred = NULL; }