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 --- mm/page_alloc.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4fbe211340e0..b93cc79a8db4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3701,7 +3701,7 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla #endif /* CONFIG_COMPACTION */ #ifdef CONFIG_LOCKDEP -struct lockdep_map __fs_reclaim_map = +static struct lockdep_map __fs_reclaim_map = STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map); static bool __need_fs_reclaim(gfp_t gfp_mask) @@ -3726,17 +3726,27 @@ static bool __need_fs_reclaim(gfp_t gfp_mask) return true; } +void __fs_reclaim_acquire(void) +{ + lock_map_acquire(&__fs_reclaim_map); +} + +void __fs_reclaim_release(void) +{ + lock_map_release(&__fs_reclaim_map); +} + void fs_reclaim_acquire(gfp_t gfp_mask) { if (__need_fs_reclaim(gfp_mask)) - lock_map_acquire(&__fs_reclaim_map); + __fs_reclaim_acquire(); } EXPORT_SYMBOL_GPL(fs_reclaim_acquire); void fs_reclaim_release(gfp_t gfp_mask) { if (__need_fs_reclaim(gfp_mask)) - lock_map_release(&__fs_reclaim_map); + __fs_reclaim_release(); } EXPORT_SYMBOL_GPL(fs_reclaim_release); #endif @@ -3754,8 +3764,8 @@ __perform_reclaim(gfp_t gfp_mask, unsigned int order, /* We now go into synchronous reclaim */ cpuset_memory_pressure_bump(); - noreclaim_flag = memalloc_noreclaim_save(); fs_reclaim_acquire(gfp_mask); + noreclaim_flag = memalloc_noreclaim_save(); reclaim_state.reclaimed_slab = 0; current->reclaim_state = &reclaim_state; @@ -3763,8 +3773,8 @@ __perform_reclaim(gfp_t gfp_mask, unsigned int order, ac->nodemask); current->reclaim_state = NULL; - fs_reclaim_release(gfp_mask); memalloc_noreclaim_restore(noreclaim_flag); + fs_reclaim_release(gfp_mask); cond_resched(); -- cgit v1.2.3