This patch should resolve the following bug.
=========================================================
[ INFO: possible irq lock inversion dependency detected ]
3.13.0-rc5.f2fs+ #6 Not tainted
---------------------------------------------------------
kswapd0/41 just changed the state of lock:
(&sbi->gc_mutex){+.+.-.}, at: [<ffffffffa030503e>] f2fs_balance_fs+0xae/0xd0 [f2fs]
but this lock took another, RECLAIM_FS-READ-unsafe lock in the past:
(&sbi->cp_rwsem){++++.?}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Chain exists of:
&sbi->gc_mutex --> &sbi->cp_mutex --> &sbi->cp_rwsem
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&sbi->cp_rwsem);
local_irq_disable();
lock(&sbi->gc_mutex);
lock(&sbi->cp_mutex);
<Interrupt>
lock(&sbi->gc_mutex);
*** DEADLOCK ***
This bug is due to the f2fs_balance_fs call in f2fs_write_data_page.
If f2fs_write_data_page is triggered by wbc->for_reclaim via kswapd, it should
not call f2fs_balance_fs which tries to get a mutex grabbed by original syscall
flow.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
c33ec32692