| Message ID | 20150703221223.GH5273@mtj.duckdns.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri 03-07-15 18:12:23, Tejun Heo wrote: > Hello, Jan. > > So, something like the following. It depends on other changes so > won't apply as-is. I'll repost it as part of a patchset once -rc1 > drops. > > Thanks! > > ------ 8< ------ > wb_writeback_work->single_wait/done are used for the wait mechanism > for synchronous wb_work (wb_writeback_work) items which are issued > when bdi_split_work_to_wbs() fails to allocate memory for asynchronous > wb_work items; however, there's no reason to use a separate wait > mechanism for this. bdi_split_work_to_wbs() can simply use on-stack > fallback wb_work item and separate wb_completion to wait for it. > > This patch removes wb_work->single_wait/done and the related code and > make bdi_split_work_to_wbs() use on-stack fallback wb_work and > wb_completion instead. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Suggested-by: Jan Kara <jack@suse.cz> Thanks! The patch looks good. You can add: Reviewed-by: Jan Kara <jack@suse.com> Honza > --- > fs/fs-writeback.c | 116 +++++++++++++----------------------------------------- > 1 file changed, 30 insertions(+), 86 deletions(-) > > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -53,8 +53,6 @@ struct wb_writeback_work { > unsigned int for_background:1; > unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ > unsigned int auto_free:1; /* free on completion */ > - unsigned int single_wait:1; > - unsigned int single_done:1; > enum wb_reason reason; /* why was writeback initiated? */ > > struct list_head list; /* pending work list */ > @@ -181,11 +179,8 @@ static void wb_queue_work(struct bdi_wri > trace_writeback_queue(wb->bdi, work); > > spin_lock_bh(&wb->work_lock); > - if (!test_bit(WB_registered, &wb->state)) { > - if (work->single_wait) > - work->single_done = 1; > + 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); > @@ -737,32 +732,6 @@ int inode_congested(struct inode *inode, > EXPORT_SYMBOL_GPL(inode_congested); > > /** > - * wb_wait_for_single_work - wait for completion of a single bdi_writeback_work > - * @bdi: bdi the work item was issued to > - * @work: work item to wait for > - * > - * Wait for the completion of @work which was issued to one of @bdi's > - * bdi_writeback's. The caller must have set @work->single_wait before > - * issuing it. This wait operates independently fo > - * wb_wait_for_completion() and also disables automatic freeing of @work. > - */ > -static void wb_wait_for_single_work(struct backing_dev_info *bdi, > - struct wb_writeback_work *work) > -{ > - if (WARN_ON_ONCE(!work->single_wait)) > - return; > - > - wait_event(bdi->wb_waitq, work->single_done); > - > - /* > - * Paired with smp_wmb() in wb_do_writeback() and ensures that all > - * modifications to @work prior to assertion of ->single_done is > - * visible to the caller once this function returns. > - */ > - smp_rmb(); > -} > - > -/** > * wb_split_bdi_pages - split nr_pages to write according to bandwidth > * @wb: target bdi_writeback to split @nr_pages to > * @nr_pages: number of pages to write for the whole bdi > @@ -791,38 +760,6 @@ static long wb_split_bdi_pages(struct bd > } > > /** > - * wb_clone_and_queue_work - clone a wb_writeback_work and issue it to a wb > - * @wb: target bdi_writeback > - * @base_work: source wb_writeback_work > - * > - * Try to make a clone of @base_work and issue it to @wb. If cloning > - * succeeds, %true is returned; otherwise, @base_work is issued directly > - * and %false is returned. In the latter case, the caller is required to > - * wait for @base_work's completion using wb_wait_for_single_work(). > - * > - * A clone is auto-freed on completion. @base_work never is. > - */ > -static bool wb_clone_and_queue_work(struct bdi_writeback *wb, > - struct wb_writeback_work *base_work) > -{ > - struct wb_writeback_work *work; > - > - work = kmalloc(sizeof(*work), GFP_ATOMIC); > - if (work) { > - *work = *base_work; > - work->auto_free = 1; > - work->single_wait = 0; > - } else { > - work = base_work; > - work->auto_free = 0; > - work->single_wait = 1; > - } > - work->single_done = 0; > - wb_queue_work(wb, work); > - return work != base_work; > -} > - > -/** > * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi > * @bdi: target backing_dev_info > * @base_work: wb_writeback_work to issue > @@ -837,7 +774,6 @@ static void bdi_split_work_to_wbs(struct > struct wb_writeback_work *base_work, > bool skip_if_busy) > { > - long nr_pages = base_work->nr_pages; > int next_memcg_id = 0; > struct bdi_writeback *wb; > struct wb_iter iter; > @@ -849,17 +785,39 @@ static void bdi_split_work_to_wbs(struct > restart: > rcu_read_lock(); > bdi_for_each_wb(wb, bdi, &iter, next_memcg_id) { > + DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done); > + struct wb_writeback_work fallback_work; > + struct wb_writeback_work *work; > + long nr_pages; > + > if (!wb_has_dirty_io(wb) || > (skip_if_busy && writeback_in_progress(wb))) > continue; > > - base_work->nr_pages = wb_split_bdi_pages(wb, nr_pages); > - if (!wb_clone_and_queue_work(wb, base_work)) { > - next_memcg_id = wb->memcg_css->id + 1; > - rcu_read_unlock(); > - wb_wait_for_single_work(bdi, base_work); > - goto restart; > + nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages); > + > + work = kmalloc(sizeof(*work), GFP_ATOMIC); > + if (work) { > + *work = *base_work; > + work->nr_pages = nr_pages; > + work->auto_free = 1; > + wb_queue_work(wb, work); > + continue; > } > + > + /* alloc failed, execute synchronously using on-stack fallback */ > + work = &fallback_work; > + *work = *base_work; > + work->nr_pages = nr_pages; > + work->auto_free = 0; > + work->done = &fallback_work_done; > + > + wb_queue_work(wb, work); > + > + next_memcg_id = wb->memcg_css->id + 1; > + rcu_read_unlock(); > + wb_wait_for_completion(bdi, &fallback_work_done); > + goto restart; > } > rcu_read_unlock(); > } > @@ -901,8 +859,6 @@ static void bdi_split_work_to_wbs(struct > if (bdi_has_dirty_io(bdi) && > (!skip_if_busy || !writeback_in_progress(&bdi->wb))) { > base_work->auto_free = 0; > - base_work->single_wait = 0; > - base_work->single_done = 0; > wb_queue_work(&bdi->wb, base_work); > } > } > @@ -1793,26 +1749,14 @@ static long wb_do_writeback(struct bdi_w > set_bit(WB_writeback_running, &wb->state); > while ((work = get_next_work_item(wb)) != NULL) { > struct wb_completion *done = work->done; > - bool need_wake_up = false; > > trace_writeback_exec(wb->bdi, work); > > wrote += wb_writeback(wb, work); > > - if (work->single_wait) { > - WARN_ON_ONCE(work->auto_free); > - /* paired w/ rmb in wb_wait_for_single_work() */ > - smp_wmb(); > - work->single_done = 1; > - need_wake_up = true; > - } else if (work->auto_free) { > + if (work->auto_free) > kfree(work); > - } > - > if (done && atomic_dec_and_test(&done->cnt)) > - need_wake_up = true; > - > - if (need_wake_up) > wake_up_all(&wb->bdi->wb_waitq); > } >
--- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -53,8 +53,6 @@ struct wb_writeback_work { unsigned int for_background:1; unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ unsigned int auto_free:1; /* free on completion */ - unsigned int single_wait:1; - unsigned int single_done:1; enum wb_reason reason; /* why was writeback initiated? */ struct list_head list; /* pending work list */ @@ -181,11 +179,8 @@ static void wb_queue_work(struct bdi_wri trace_writeback_queue(wb->bdi, work); spin_lock_bh(&wb->work_lock); - if (!test_bit(WB_registered, &wb->state)) { - if (work->single_wait) - work->single_done = 1; + 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); @@ -737,32 +732,6 @@ int inode_congested(struct inode *inode, EXPORT_SYMBOL_GPL(inode_congested); /** - * wb_wait_for_single_work - wait for completion of a single bdi_writeback_work - * @bdi: bdi the work item was issued to - * @work: work item to wait for - * - * Wait for the completion of @work which was issued to one of @bdi's - * bdi_writeback's. The caller must have set @work->single_wait before - * issuing it. This wait operates independently fo - * wb_wait_for_completion() and also disables automatic freeing of @work. - */ -static void wb_wait_for_single_work(struct backing_dev_info *bdi, - struct wb_writeback_work *work) -{ - if (WARN_ON_ONCE(!work->single_wait)) - return; - - wait_event(bdi->wb_waitq, work->single_done); - - /* - * Paired with smp_wmb() in wb_do_writeback() and ensures that all - * modifications to @work prior to assertion of ->single_done is - * visible to the caller once this function returns. - */ - smp_rmb(); -} - -/** * wb_split_bdi_pages - split nr_pages to write according to bandwidth * @wb: target bdi_writeback to split @nr_pages to * @nr_pages: number of pages to write for the whole bdi @@ -791,38 +760,6 @@ static long wb_split_bdi_pages(struct bd } /** - * wb_clone_and_queue_work - clone a wb_writeback_work and issue it to a wb - * @wb: target bdi_writeback - * @base_work: source wb_writeback_work - * - * Try to make a clone of @base_work and issue it to @wb. If cloning - * succeeds, %true is returned; otherwise, @base_work is issued directly - * and %false is returned. In the latter case, the caller is required to - * wait for @base_work's completion using wb_wait_for_single_work(). - * - * A clone is auto-freed on completion. @base_work never is. - */ -static bool wb_clone_and_queue_work(struct bdi_writeback *wb, - struct wb_writeback_work *base_work) -{ - struct wb_writeback_work *work; - - work = kmalloc(sizeof(*work), GFP_ATOMIC); - if (work) { - *work = *base_work; - work->auto_free = 1; - work->single_wait = 0; - } else { - work = base_work; - work->auto_free = 0; - work->single_wait = 1; - } - work->single_done = 0; - wb_queue_work(wb, work); - return work != base_work; -} - -/** * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi * @bdi: target backing_dev_info * @base_work: wb_writeback_work to issue @@ -837,7 +774,6 @@ static void bdi_split_work_to_wbs(struct struct wb_writeback_work *base_work, bool skip_if_busy) { - long nr_pages = base_work->nr_pages; int next_memcg_id = 0; struct bdi_writeback *wb; struct wb_iter iter; @@ -849,17 +785,39 @@ static void bdi_split_work_to_wbs(struct restart: rcu_read_lock(); bdi_for_each_wb(wb, bdi, &iter, next_memcg_id) { + DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done); + struct wb_writeback_work fallback_work; + struct wb_writeback_work *work; + long nr_pages; + if (!wb_has_dirty_io(wb) || (skip_if_busy && writeback_in_progress(wb))) continue; - base_work->nr_pages = wb_split_bdi_pages(wb, nr_pages); - if (!wb_clone_and_queue_work(wb, base_work)) { - next_memcg_id = wb->memcg_css->id + 1; - rcu_read_unlock(); - wb_wait_for_single_work(bdi, base_work); - goto restart; + nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages); + + work = kmalloc(sizeof(*work), GFP_ATOMIC); + if (work) { + *work = *base_work; + work->nr_pages = nr_pages; + work->auto_free = 1; + wb_queue_work(wb, work); + continue; } + + /* alloc failed, execute synchronously using on-stack fallback */ + work = &fallback_work; + *work = *base_work; + work->nr_pages = nr_pages; + work->auto_free = 0; + work->done = &fallback_work_done; + + wb_queue_work(wb, work); + + next_memcg_id = wb->memcg_css->id + 1; + rcu_read_unlock(); + wb_wait_for_completion(bdi, &fallback_work_done); + goto restart; } rcu_read_unlock(); } @@ -901,8 +859,6 @@ static void bdi_split_work_to_wbs(struct if (bdi_has_dirty_io(bdi) && (!skip_if_busy || !writeback_in_progress(&bdi->wb))) { base_work->auto_free = 0; - base_work->single_wait = 0; - base_work->single_done = 0; wb_queue_work(&bdi->wb, base_work); } } @@ -1793,26 +1749,14 @@ static long wb_do_writeback(struct bdi_w set_bit(WB_writeback_running, &wb->state); while ((work = get_next_work_item(wb)) != NULL) { struct wb_completion *done = work->done; - bool need_wake_up = false; trace_writeback_exec(wb->bdi, work); wrote += wb_writeback(wb, work); - if (work->single_wait) { - WARN_ON_ONCE(work->auto_free); - /* paired w/ rmb in wb_wait_for_single_work() */ - smp_wmb(); - work->single_done = 1; - need_wake_up = true; - } else if (work->auto_free) { + if (work->auto_free) kfree(work); - } - if (done && atomic_dec_and_test(&done->cnt)) - need_wake_up = true; - - if (need_wake_up) wake_up_all(&wb->bdi->wb_waitq); }
Hello, Jan. So, something like the following. It depends on other changes so won't apply as-is. I'll repost it as part of a patchset once -rc1 drops. Thanks! ------ 8< ------ wb_writeback_work->single_wait/done are used for the wait mechanism for synchronous wb_work (wb_writeback_work) items which are issued when bdi_split_work_to_wbs() fails to allocate memory for asynchronous wb_work items; however, there's no reason to use a separate wait mechanism for this. bdi_split_work_to_wbs() can simply use on-stack fallback wb_work item and separate wb_completion to wait for it. This patch removes wb_work->single_wait/done and the related code and make bdi_split_work_to_wbs() use on-stack fallback wb_work and wb_completion instead. Signed-off-by: Tejun Heo <tj@kernel.org> Suggested-by: Jan Kara <jack@suse.cz> --- fs/fs-writeback.c | 116 +++++++++++++----------------------------------------- 1 file changed, 30 insertions(+), 86 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html