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authorOmar Sandoval <osandov@fb.com>2018-06-08 03:07:02 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-08 03:34:35 +0300
commit93781325da6e07af57a21f111d1f2b9f128fa397 (patch)
tree35542710adcf686003dadb55d3e6ae20036a3d36 /include/linux/sched
parent89fdcd262fd40712da65e922558872a12b203332 (diff)
downloadlinux-93781325da6e07af57a21f111d1f2b9f128fa397.tar.xz
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 <osandov@fb.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/sched')
-rw-r--r--include/linux/sched/mm.h4
1 files changed, 4 insertions, 0 deletions
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