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Commit 2fefd558 authored by Zhao Lei's avatar Zhao Lei Committed by David Sterba
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btrfs: reada: limit max works count 



Reada creates 2 works for each level of tree recursively.

In case of a tree having many levels, the number of created works
is 2^level_of_tree.
Actually we don't need so many works in parallel, this patch limits
max works to BTRFS_MAX_MIRRORS * 2.

The per-fs works_counter will be also used for btrfs_reada_wait() to
check is there are background workers.

Signed-off-by: default avatarZhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 895a11b8

fs/btrfs/ctree.h

+3 −0
Original line number Diff line number Diff line
@@ -1822,6 +1822,9 @@ struct btrfs_fs_info { 
	spinlock_t reada_lock;

	struct radix_tree_root reada_tree;



	/* readahead works cnt */

	atomic_t reada_works_cnt;



	/* Extent buffer radix tree */

	spinlock_t buffer_lock;

	struct radix_tree_root buffer_radix;

fs/btrfs/disk-io.c

+1 −0
Original line number Diff line number Diff line
@@ -2603,6 +2603,7 @@ int open_ctree(struct super_block *sb, 
	atomic_set(&fs_info->nr_async_bios, 0);

	atomic_set(&fs_info->defrag_running, 0);

	atomic_set(&fs_info->qgroup_op_seq, 0);

	atomic_set(&fs_info->reada_works_cnt, 0);

	atomic64_set(&fs_info->tree_mod_seq, 0);

	fs_info->sb = sb;

	fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE;

fs/btrfs/reada.c

+8 −1
Original line number Diff line number Diff line
@@ -748,6 +748,8 @@ static void reada_start_machine_worker(struct btrfs_work *work) 
	set_task_ioprio(current, BTRFS_IOPRIO_READA);

	__reada_start_machine(fs_info);

	set_task_ioprio(current, old_ioprio);



	atomic_dec(&fs_info->reada_works_cnt);

}



static void __reada_start_machine(struct btrfs_fs_info *fs_info)
@@ -779,8 +781,12 @@ static void __reada_start_machine(struct btrfs_fs_info *fs_info) 
	 * enqueue to workers to finish it. This will distribute the load to

	 * the cores.

	 */

	for (i = 0; i < 2; ++i)

	for (i = 0; i < 2; ++i) {

		reada_start_machine(fs_info);

		if (atomic_read(&fs_info->reada_works_cnt) >

		    BTRFS_MAX_MIRRORS * 2)

			break;

	}

}



static void reada_start_machine(struct btrfs_fs_info *fs_info)
@@ -797,6 +803,7 @@ static void reada_start_machine(struct btrfs_fs_info *fs_info) 
	rmw->fs_info = fs_info;



	btrfs_queue_work(fs_info->readahead_workers, &rmw->work);

	atomic_inc(&fs_info->reada_works_cnt);

}



#ifdef DEBUG