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[49.179.0.188]) by smtp.gmail.com with ESMTPSA id jh21-20020a170903329500b001ae6fe84244sm1912225plb.243.2023.05.31.16.00.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 May 2023 16:00:27 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1q4Unp-006Hhv-1I; Thu, 01 Jun 2023 09:00:25 +1000 Date: Thu, 1 Jun 2023 09:00:25 +1000 From: Dave Chinner To: Qi Zheng Cc: akpm@linux-foundation.org, tkhai@ya.ru, roman.gushchin@linux.dev, vbabka@suse.cz, viro@zeniv.linux.org.uk, brauner@kernel.org, djwong@kernel.org, hughd@google.com, paulmck@kernel.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, Qi Zheng Subject: Re: [PATCH 3/8] fs: move list_lru_destroy() to destroy_super_work() Message-ID: References: <20230531095742.2480623-1-qi.zheng@linux.dev> <20230531095742.2480623-4-qi.zheng@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230531095742.2480623-4-qi.zheng@linux.dev> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, May 31, 2023 at 09:57:37AM +0000, Qi Zheng wrote: > From: Kirill Tkhai > > The patch makes s_dentry_lru and s_inode_lru be destroyed > later from the workqueue. This is preparation to split > unregister_shrinker(super_block::s_shrink) in two stages, > and to call finalize stage from destroy_super_work(). > > Note, that generic filesystem shrinker unregistration > is safe to be split in two stages right after this > patch, since super_cache_count() and super_cache_scan() > have a deal with s_dentry_lru and s_inode_lru only. > > But there are two exceptions: XFS and SHMEM, which > define .nr_cached_objects() and .free_cached_objects() > callbacks. These two do not allow us to do the splitting > right after this patch. They touch fs-specific data, > which is destroyed earlier, than destroy_super_work(). > So, we can't call unregister_shrinker_delayed_finalize() > from destroy_super_work() because of them, and next > patches make preparations to make this possible. > > Signed-off-by: Kirill Tkhai > Signed-off-by: Qi Zheng > --- > fs/super.c | 17 +++++------------ > 1 file changed, 5 insertions(+), 12 deletions(-) > > diff --git a/fs/super.c b/fs/super.c > index 8d8d68799b34..2ce4c72720f3 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -159,6 +159,11 @@ static void destroy_super_work(struct work_struct *work) > destroy_work); > int i; > > + WARN_ON(list_lru_count(&s->s_dentry_lru)); > + WARN_ON(list_lru_count(&s->s_inode_lru)); > + list_lru_destroy(&s->s_dentry_lru); > + list_lru_destroy(&s->s_inode_lru); > + > for (i = 0; i < SB_FREEZE_LEVELS; i++) > percpu_free_rwsem(&s->s_writers.rw_sem[i]); > kfree(s); > @@ -177,8 +182,6 @@ static void destroy_unused_super(struct super_block *s) > if (!s) > return; > up_write(&s->s_umount); > - list_lru_destroy(&s->s_dentry_lru); > - list_lru_destroy(&s->s_inode_lru); > security_sb_free(s); > put_user_ns(s->s_user_ns); > kfree(s->s_subtype); > @@ -287,8 +290,6 @@ static void __put_super(struct super_block *s) > { > if (!--s->s_count) { > list_del_init(&s->s_list); > - WARN_ON(s->s_dentry_lru.node); > - WARN_ON(s->s_inode_lru.node); Why are you removing the wanrings from here? Regardless of where we tear down the lru lists, they *must* be empty here otherwise we have a memory leak. Hence I don't think these warnings should be moved at all. Cheers, Dave. -- Dave Chinner david@fromorbit.com