Commit f0fad8a5 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

writeback: merely wakeup flusher thread if work allocation fails for WB_SYNC_NONE

Since it's an opportunistic writeback and not a data integrity action,
don't punt to blocking writeback. Just wakeup the thread and it will
flush old data.
Acked-by: default avatarJan Kara <>
Signed-off-by: default avatarChristoph Hellwig <>
Signed-off-by: default avatarJens Axboe <>
parent 1fe06ad8
......@@ -75,13 +75,6 @@ static inline void bdi_work_init(struct bdi_work *work,
work->state = WS_USED;
static inline void bdi_work_init_on_stack(struct bdi_work *work,
struct writeback_control *wbc)
bdi_work_init(work, wbc);
work->state |= WS_ONSTACK;
* writeback_in_progress - determine whether there is writeback in progress
* @bdi: the device's backing_dev_info structure.
......@@ -207,34 +200,23 @@ static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
void bdi_start_writeback(struct writeback_control *wbc)
const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
struct bdi_work work_stack, *work = NULL;
if (!must_wait)
work = bdi_alloc_work(wbc);
* WB_SYNC_NONE is opportunistic writeback. If this allocation fails,
* bdi_queue_work() will wake up the thread and flush old data. This
* should ensure some amount of progress in freeing memory.
if (wbc->sync_mode != WB_SYNC_ALL) {
struct bdi_work *w = bdi_alloc_work(wbc);
if (!work) {
work = &work_stack;
bdi_work_init_on_stack(work, wbc);
bdi_queue_work(wbc->bdi, w);
} else {
struct bdi_work work;
bdi_queue_work(wbc->bdi, work);
bdi_work_init(&work, wbc);
work.state |= WS_ONSTACK;
* If the sync mode is WB_SYNC_ALL, block waiting for the work to
* complete. If not, we only need to wait for the work to be started,
* if we allocated it on-stack. We use the same mechanism, if the
* wait bit is set in the bdi_work struct, then threads will not
* clear pending until after they are done.
* Note that work == &work_stack if must_wait is true, so we don't
* need to do call_rcu() here ever, since the completion path will
* have done that for us.
if (must_wait || work == &work_stack) {
if (work != &work_stack)
call_rcu(&work->rcu_head, bdi_work_free);
bdi_queue_work(wbc->bdi, &work);
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