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/vmscan.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 9270a4370d54..0e67b477ecef 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3318,11 +3318,15 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) .may_unmap = 1, .may_swap = 1, }; + + __fs_reclaim_acquire(); + count_vm_event(PAGEOUTRUN); do { unsigned long nr_reclaimed = sc.nr_reclaimed; bool raise_priority = true; + bool ret; sc.reclaim_idx = classzone_idx; @@ -3395,7 +3399,10 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) wake_up_all(&pgdat->pfmemalloc_wait); /* Check if kswapd should be suspending */ - if (try_to_freeze() || kthread_should_stop()) + __fs_reclaim_release(); + ret = try_to_freeze(); + __fs_reclaim_acquire(); + if (ret || kthread_should_stop()) break; /* @@ -3412,6 +3419,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) out: snapshot_refaults(NULL, pgdat); + __fs_reclaim_release(); /* * Return the order kswapd stopped reclaiming at as * prepare_kswapd_sleep() takes it into account. If another caller @@ -3600,9 +3608,7 @@ kswapd_try_sleep: */ trace_mm_vmscan_kswapd_wake(pgdat->node_id, classzone_idx, alloc_order); - fs_reclaim_acquire(GFP_KERNEL); reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx); - fs_reclaim_release(GFP_KERNEL); if (reclaim_order < alloc_order) goto kswapd_try_sleep; } @@ -3684,16 +3690,16 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim) unsigned long nr_reclaimed; unsigned int noreclaim_flag; - noreclaim_flag = memalloc_noreclaim_save(); fs_reclaim_acquire(sc.gfp_mask); + noreclaim_flag = memalloc_noreclaim_save(); reclaim_state.reclaimed_slab = 0; p->reclaim_state = &reclaim_state; nr_reclaimed = do_try_to_free_pages(zonelist, &sc); p->reclaim_state = NULL; - fs_reclaim_release(sc.gfp_mask); memalloc_noreclaim_restore(noreclaim_flag); + fs_reclaim_release(sc.gfp_mask); return nr_reclaimed; } @@ -3870,6 +3876,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in }; cond_resched(); + fs_reclaim_acquire(sc.gfp_mask); /* * We need to be able to allocate from the reserves for RECLAIM_UNMAP * and we also need to be able to write out pages for RECLAIM_WRITE @@ -3877,7 +3884,6 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in */ noreclaim_flag = memalloc_noreclaim_save(); p->flags |= PF_SWAPWRITE; - fs_reclaim_acquire(sc.gfp_mask); reclaim_state.reclaimed_slab = 0; p->reclaim_state = &reclaim_state; @@ -3892,9 +3898,9 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in } p->reclaim_state = NULL; - fs_reclaim_release(gfp_mask); current->flags &= ~PF_SWAPWRITE; memalloc_noreclaim_restore(noreclaim_flag); + fs_reclaim_release(sc.gfp_mask); return sc.nr_reclaimed >= nr_pages; } -- cgit v1.2.3