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Commit 34f8fe50 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5b9cce4c

include/linux/backing-dev-defs.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

include/linux/backing-dev.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

mm/backing-dev.c

+63 −2
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only



#include <linux/wait.h>

#include <linux/rbtree.h>

#include <linux/backing-dev.h>

#include <linux/kthread.h>

#include <linux/freezer.h>
@@ -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);