bdi: Add bdi->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. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -185,6 +185,8 @@ struct bdi_writeback {
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};
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};
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struct backing_dev_info {
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struct backing_dev_info {
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u64 id;
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struct rb_node rb_node; /* keyed by ->id */
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struct list_head bdi_list;
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struct list_head bdi_list;
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unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
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unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
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unsigned long io_pages; /* max allowed IO size */
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unsigned long io_pages; /* max allowed IO size */
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@ -24,6 +24,7 @@ static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
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return bdi;
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return bdi;
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}
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}
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struct backing_dev_info *bdi_get_by_id(u64 id);
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void bdi_put(struct backing_dev_info *bdi);
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void bdi_put(struct backing_dev_info *bdi);
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__printf(2, 3)
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__printf(2, 3)
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@ -1,6 +1,7 @@
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// SPDX-License-Identifier: GPL-2.0-only
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// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/wait.h>
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#include <linux/wait.h>
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#include <linux/rbtree.h>
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#include <linux/backing-dev.h>
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#include <linux/backing-dev.h>
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#include <linux/kthread.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/freezer.h>
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@ -22,10 +23,12 @@ EXPORT_SYMBOL_GPL(noop_backing_dev_info);
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static struct class *bdi_class;
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static struct class *bdi_class;
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/*
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/*
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* bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
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* bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
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* locking.
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* reader side locking.
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*/
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*/
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DEFINE_SPINLOCK(bdi_lock);
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DEFINE_SPINLOCK(bdi_lock);
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static u64 bdi_id_cursor;
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static struct rb_root bdi_tree = RB_ROOT;
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LIST_HEAD(bdi_list);
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LIST_HEAD(bdi_list);
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/* bdi_wq serves all asynchronous writeback tasks */
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/* bdi_wq serves all asynchronous writeback tasks */
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@ -859,9 +862,58 @@ struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
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}
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}
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EXPORT_SYMBOL(bdi_alloc_node);
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EXPORT_SYMBOL(bdi_alloc_node);
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static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
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{
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struct rb_node **p = &bdi_tree.rb_node;
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struct rb_node *parent = NULL;
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struct backing_dev_info *bdi;
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lockdep_assert_held(&bdi_lock);
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while (*p) {
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parent = *p;
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bdi = rb_entry(parent, struct backing_dev_info, rb_node);
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if (bdi->id > id)
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p = &(*p)->rb_left;
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else if (bdi->id < id)
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p = &(*p)->rb_right;
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else
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break;
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}
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if (parentp)
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*parentp = parent;
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return p;
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}
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/**
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* bdi_get_by_id - lookup and get bdi from its id
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* @id: bdi id to lookup
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*
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* Find bdi matching @id and get it. Returns NULL if the matching bdi
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* doesn't exist or is already unregistered.
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*/
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struct backing_dev_info *bdi_get_by_id(u64 id)
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{
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struct backing_dev_info *bdi = NULL;
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struct rb_node **p;
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spin_lock_bh(&bdi_lock);
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p = bdi_lookup_rb_node(id, NULL);
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if (*p) {
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bdi = rb_entry(*p, struct backing_dev_info, rb_node);
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bdi_get(bdi);
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}
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spin_unlock_bh(&bdi_lock);
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return bdi;
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}
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int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
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int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
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{
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{
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struct device *dev;
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struct device *dev;
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struct rb_node *parent, **p;
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if (bdi->dev) /* The driver needs to use separate queues per device */
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if (bdi->dev) /* The driver needs to use separate queues per device */
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return 0;
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return 0;
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@ -877,7 +929,15 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
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set_bit(WB_registered, &bdi->wb.state);
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set_bit(WB_registered, &bdi->wb.state);
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spin_lock_bh(&bdi_lock);
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spin_lock_bh(&bdi_lock);
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bdi->id = ++bdi_id_cursor;
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p = bdi_lookup_rb_node(bdi->id, &parent);
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rb_link_node(&bdi->rb_node, parent, p);
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rb_insert_color(&bdi->rb_node, &bdi_tree);
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list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
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list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
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spin_unlock_bh(&bdi_lock);
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spin_unlock_bh(&bdi_lock);
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trace_writeback_bdi_register(bdi);
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trace_writeback_bdi_register(bdi);
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@ -918,6 +978,7 @@ EXPORT_SYMBOL(bdi_register_owner);
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static void bdi_remove_from_list(struct backing_dev_info *bdi)
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static void bdi_remove_from_list(struct backing_dev_info *bdi)
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{
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{
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spin_lock_bh(&bdi_lock);
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spin_lock_bh(&bdi_lock);
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rb_erase(&bdi->rb_node, &bdi_tree);
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list_del_rcu(&bdi->bdi_list);
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list_del_rcu(&bdi->bdi_list);
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spin_unlock_bh(&bdi_lock);
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spin_unlock_bh(&bdi_lock);
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