Re: [PATCH 1/1] writeback fix bdi thread race in mark_inode_dirty

[Jens Axboe <axboe@kernel.dk>]

On Fri, Jul 19 2013, Srinivas Eeda wrote:
> In __mark_inode_dirty, a process checks !wb_has_dirty_io outside of list_lock
> spinlock. This could cause a race, where process sees that list has dirty io
> and decides not wake up bdi thread and waits for spinlock to add to dirty list.
> Right at this time bdi_writeback_workfn finished write-back on last inode.
> It sees the list is empty and ends. Process could now get the spinlock and
> add inode to dirty list and doesn't wakeup bdi thread. Future calls to
> __mark_inode_dirty also do not wake up the thread because list is not empty
> any more.
> 
> Fix is to get wb.list_lock spinlock before checking the dirty list

With Jan's ack, lets add this for the current cycle. Should go into
stable as well, imho.

-- 
Jens Axboe