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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: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Zhao Lei 2016-01-07 18:38:48 +08:00 committed by David Sterba
parent 895a11b868
commit 2fefd5583f
3 changed files with 12 additions and 1 deletions
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3
fs/btrfs/ctree.h
View File

@ -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;

1
fs/btrfs/disk-io.c
View File

@ -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;

9
fs/btrfs/reada.c
View File

@ -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