If the completion of a wb_writeback_work can be waited upon by setting its ->done to a struct completion and waiting on it; however, for cgroup writeback support, it's necessary to issue multiple work items to multiple bdi_writebacks and wait for the completion of all. This patch implements wb_completion which can wait for multiple work items and replaces the struct completion with it. It can be defined using DEFINE_WB_COMPLETION_ONSTACK(), used for multiple work items and waited for by wb_wait_for_completion(). Nobody currently issues multiple work items and this patch doesn't introduce any behavior changes. Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> --- fs/fs-writeback.c | 57 +++++++++++++++++++++++++++++++--------- include/linux/backing-dev-defs.h | 2 ++ mm/backing-dev.c | 1 + 3 files changed, 48 insertions(+), 12 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 3c012b8..6527692 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -34,6 +34,10 @@ */ #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10)) +struct wb_completion { + atomic_t cnt; +}; + /* * Passed into wb_writeback(), essentially a subset of writeback_control */ @@ -51,9 +55,21 @@ struct wb_writeback_work { enum wb_reason reason; /* why was writeback initiated? */ struct list_head list; /* pending work list */ - struct completion *done; /* set if the caller waits */ + struct wb_completion *done; /* set if the caller waits */ }; +/* + * If one wants to wait for one or more wb_writeback_works, each work's + * ->done should be set to a wb_completion defined using the following + * macro. Once all work items are issued with wb_queue_work(), the caller + * can wait for the completion of all using wb_wait_for_completion(). Work + * items which are waited upon aren't freed automatically on completion. + */ +#define DEFINE_WB_COMPLETION_ONSTACK(cmpl) \ + struct wb_completion cmpl = { \ + .cnt = ATOMIC_INIT(1), \ + } + static inline struct inode *wb_inode(struct list_head *head) { return list_entry(head, struct inode, i_wb_list); @@ -83,17 +99,34 @@ static void wb_queue_work(struct bdi_writeback *wb, trace_writeback_queue(wb->bdi, work); spin_lock_bh(&wb->work_lock); - if (!test_bit(WB_registered, &wb->state)) { - if (work->done) - complete(work->done); + if (!test_bit(WB_registered, &wb->state)) goto out_unlock; - } + if (work->done) + atomic_inc(&work->done->cnt); list_add_tail(&work->list, &wb->work_list); mod_delayed_work(bdi_wq, &wb->dwork, 0); out_unlock: spin_unlock_bh(&wb->work_lock); } +/** + * wb_wait_for_completion - wait for completion of bdi_writeback_works + * @bdi: bdi work items were issued to + * @done: target wb_completion + * + * Wait for one or more work items issued to @bdi with their ->done field + * set to @done, which should have been defined with + * DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such + * work items are completed. Work items which are waited upon aren't freed + * automatically on completion. + */ +static void wb_wait_for_completion(struct backing_dev_info *bdi, + struct wb_completion *done) +{ + atomic_dec(&done->cnt); /* put down the initial count */ + wait_event(bdi->wb_waitq, !atomic_read(&done->cnt)); +} + #ifdef CONFIG_CGROUP_WRITEBACK /** @@ -1175,7 +1208,7 @@ static long wb_do_writeback(struct bdi_writeback *wb) set_bit(WB_writeback_running, &wb->state); while ((work = get_next_work_item(wb)) != NULL) { - struct completion *done = work->done; + struct wb_completion *done = work->done; trace_writeback_exec(wb->bdi, work); @@ -1183,8 +1216,8 @@ static long wb_do_writeback(struct bdi_writeback *wb) if (work->auto_free) kfree(work); - if (done) - complete(done); + if (done && atomic_dec_and_test(&done->cnt)) + wake_up_all(&wb->bdi->wb_waitq); } /* @@ -1482,7 +1515,7 @@ void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr, enum wb_reason reason) { - DECLARE_COMPLETION_ONSTACK(done); + DEFINE_WB_COMPLETION_ONSTACK(done); struct wb_writeback_work work = { .sb = sb, .sync_mode = WB_SYNC_NONE, @@ -1497,7 +1530,7 @@ void writeback_inodes_sb_nr(struct super_block *sb, return; WARN_ON(!rwsem_is_locked(&sb->s_umount)); wb_queue_work(&bdi->wb, &work); - wait_for_completion(&done); + wb_wait_for_completion(bdi, &done); } EXPORT_SYMBOL(writeback_inodes_sb_nr); @@ -1564,7 +1597,7 @@ EXPORT_SYMBOL(try_to_writeback_inodes_sb); */ void sync_inodes_sb(struct super_block *sb) { - DECLARE_COMPLETION_ONSTACK(done); + DEFINE_WB_COMPLETION_ONSTACK(done); struct wb_writeback_work work = { .sb = sb, .sync_mode = WB_SYNC_ALL, @@ -1582,7 +1615,7 @@ void sync_inodes_sb(struct super_block *sb) WARN_ON(!rwsem_is_locked(&sb->s_umount)); wb_queue_work(&bdi->wb, &work); - wait_for_completion(&done); + wb_wait_for_completion(bdi, &done); wait_sb_inodes(sb); } diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index 4ceda83..bc1b9e7 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -110,6 +110,8 @@ struct backing_dev_info { #ifdef CONFIG_CGROUP_WRITEBACK struct radix_tree_root cgwb_tree; /* radix tree of !root cgroup wbs */ #endif + wait_queue_head_t wb_waitq; + struct device *dev; struct timer_list laptop_mode_wb_timer; diff --git a/mm/backing-dev.c b/mm/backing-dev.c index b4a5d9b..171fffd 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -631,6 +631,7 @@ int bdi_init(struct backing_dev_info *bdi) bdi->max_ratio = 100; bdi->max_prop_frac = FPROP_FRAC_BASE; INIT_LIST_HEAD(&bdi->bdi_list); + init_waitqueue_head(&bdi->wb_waitq); err = wb_init(&bdi->wb, bdi, GFP_KERNEL); if (err) -- 2.1.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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