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authorOmar Sandoval <osandov@fb.com>2018-06-07 17:07:02 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-07 17:34:35 -0700
commit93781325da6e07af57a21f111d1f2b9f128fa397 (patch)
tree35542710adcf686003dadb55d3e6ae20036a3d36 /mm/page_alloc.c
parent89fdcd262fd40712da65e922558872a12b203332 (diff)
downloadlwn-93781325da6e07af57a21f111d1f2b9f128fa397.tar.gz
lwn-93781325da6e07af57a21f111d1f2b9f128fa397.zip
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 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c20
1 files changed, 15 insertions, 5 deletions
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();