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Mon, 26 Aug 2019 09:07:08 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::d081]) by smtp.gmail.com with ESMTPSA id r15sm6633892qtp.94.2019.08.26.09.07.07 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Aug 2019 09:07:07 -0700 (PDT) From: Tejun Heo To: axboe@kernel.dk, jack@suse.cz, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, guro@fb.com, akpm@linux-foundation.org, Tejun Heo Subject: [PATCH 2/5] bdi: Add bdi->id Date: Mon, 26 Aug 2019 09:06:53 -0700 Message-Id: <20190826160656.870307-3-tj@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190826160656.870307-1-tj@kernel.org> References: <20190826160656.870307-1-tj@kernel.org> 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: There currently is no way to universally identify and lookup a bdi without holding a reference and pointer to it. This patch adds an non-recycling bdi->id and implements bdi_get_by_id() which looks up bdis by their ids. This will be used by memcg foreign inode flushing. I left bdi_list alone for simplicity and because while rb_tree does support rcu assignment it doesn't seem to guarantee lossless walk when walk is racing aginst tree rebalance operations. Signed-off-by: Tejun Heo Reviewed-by: Jan Kara --- include/linux/backing-dev-defs.h | 2 + include/linux/backing-dev.h | 1 + mm/backing-dev.c | 65 +++++++++++++++++++++++++++++++- 3 files changed, 66 insertions(+), 2 deletions(-) diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index 8fb740178d5d..1075f2552cfc 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -185,6 +185,8 @@ struct bdi_writeback { }; struct backing_dev_info { + u64 id; + struct rb_node rb_node; /* keyed by ->id */ struct list_head bdi_list; unsigned long ra_pages; /* max readahead in PAGE_SIZE units */ unsigned long io_pages; /* max allowed IO size */ diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 02650b1253a2..84cdcfbc763f 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -24,6 +24,7 @@ static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi) return bdi; } +struct backing_dev_info *bdi_get_by_id(u64 id); void bdi_put(struct backing_dev_info *bdi); __printf(2, 3) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index e8e89158adec..612aa7c5ddbd 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-only #include +#include #include #include #include @@ -22,10 +23,12 @@ EXPORT_SYMBOL_GPL(noop_backing_dev_info); static struct class *bdi_class; /* - * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side - * locking. + * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU + * reader side locking. */ DEFINE_SPINLOCK(bdi_lock); +static u64 bdi_id_cursor; +static struct rb_root bdi_tree = RB_ROOT; LIST_HEAD(bdi_list); /* bdi_wq serves all asynchronous writeback tasks */ @@ -859,9 +862,58 @@ struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id) } EXPORT_SYMBOL(bdi_alloc_node); +static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp) +{ + struct rb_node **p = &bdi_tree.rb_node; + struct rb_node *parent = NULL; + struct backing_dev_info *bdi; + + lockdep_assert_held(&bdi_lock); + + while (*p) { + parent = *p; + bdi = rb_entry(parent, struct backing_dev_info, rb_node); + + if (bdi->id > id) + p = &(*p)->rb_left; + else if (bdi->id < id) + p = &(*p)->rb_right; + else + break; + } + + if (parentp) + *parentp = parent; + return p; +} + +/** + * bdi_get_by_id - lookup and get bdi from its id + * @id: bdi id to lookup + * + * Find bdi matching @id and get it. Returns NULL if the matching bdi + * doesn't exist or is already unregistered. + */ +struct backing_dev_info *bdi_get_by_id(u64 id) +{ + struct backing_dev_info *bdi = NULL; + struct rb_node **p; + + spin_lock_bh(&bdi_lock); + p = bdi_lookup_rb_node(id, NULL); + if (*p) { + bdi = rb_entry(*p, struct backing_dev_info, rb_node); + bdi_get(bdi); + } + spin_unlock_bh(&bdi_lock); + + return bdi; +} + int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) { struct device *dev; + struct rb_node *parent, **p; if (bdi->dev) /* The driver needs to use separate queues per device */ return 0; @@ -877,7 +929,15 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) set_bit(WB_registered, &bdi->wb.state); spin_lock_bh(&bdi_lock); + + bdi->id = ++bdi_id_cursor; + + p = bdi_lookup_rb_node(bdi->id, &parent); + rb_link_node(&bdi->rb_node, parent, p); + rb_insert_color(&bdi->rb_node, &bdi_tree); + list_add_tail_rcu(&bdi->bdi_list, &bdi_list); + spin_unlock_bh(&bdi_lock); trace_writeback_bdi_register(bdi); @@ -918,6 +978,7 @@ EXPORT_SYMBOL(bdi_register_owner); static void bdi_remove_from_list(struct backing_dev_info *bdi) { spin_lock_bh(&bdi_lock); + rb_erase(&bdi->rb_node, &bdi_tree); list_del_rcu(&bdi->bdi_list); spin_unlock_bh(&bdi_lock);