From 93781325da6e07af57a21f111d1f2b9f128fa397 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Thu, 7 Jun 2018 17:07:02 -0700 Subject: lockdep: fix fs_reclaim annotation While revisiting my Btrfs swapfile series [1], I introduced a situation in which reclaim would lock i_rwsem, and even though the swapon() path clearly made GFP_KERNEL allocations while holding i_rwsem, I got no complaints from lockdep. It turns out that the rework of the fs_reclaim annotation was broken: if the current task has PF_MEMALLOC set, we don't acquire the dummy fs_reclaim lock, but when reclaiming we always check this _after_ we've just set the PF_MEMALLOC flag. In most cases, we can fix this by moving the fs_reclaim_{acquire,release}() outside of the memalloc_noreclaim_{save,restore}(), althought kswapd is slightly different. After applying this, I got the expected lockdep splats. 1: https://lwn.net/Articles/625412/ Link: http://lkml.kernel.org/r/9f8aa70652a98e98d7c4de0fc96a4addcee13efe.1523778026.git.osandov@fb.com Fixes: d92a8cfcb37e ("locking/lockdep: Rework FS_RECLAIM annotation") Signed-off-by: Omar Sandoval Reviewed-by: Andrew Morton Cc: Peter Zijlstra Cc: Tetsuo Handa Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched/mm.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/sched') diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 76a8cb4ef178..44d356f5e47c 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -163,9 +163,13 @@ static inline gfp_t current_gfp_context(gfp_t flags) } #ifdef CONFIG_LOCKDEP +extern void __fs_reclaim_acquire(void); +extern void __fs_reclaim_release(void); extern void fs_reclaim_acquire(gfp_t gfp_mask); extern void fs_reclaim_release(gfp_t gfp_mask); #else +static inline void __fs_reclaim_acquire(void) { } +static inline void __fs_reclaim_release(void) { } static inline void fs_reclaim_acquire(gfp_t gfp_mask) { } static inline void fs_reclaim_release(gfp_t gfp_mask) { } #endif -- cgit v1.2.3-59-g8ed1b