From 95d6c701f4ca7c44dc148d664f604541266a2333 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Mon, 14 Dec 2020 19:08:34 -0800 Subject: [PATCH] mm: extract might_alloc() debug check MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Extracted from slab.h, which seems to have the most complete version including the correct might_sleep() check. Roll it out to slob.c. Motivated by a discussion with Paul about possibly changing call_rcu behaviour to allocate memory, but only roughly every 500th call. There are a lot fewer places in the kernel that care about whether allocating memory is allowed or not (due to deadlocks with reclaim code) than places that care whether sleeping is allowed. But debugging these also tends to be a lot harder, so nice descriptive checks could come in handy. I might have some use eventually for annotations in drivers/gpu. Note that unlike fs_reclaim_acquire/release gfpflags_allow_blocking does not consult the PF_MEMALLOC flags. But there is no flag equivalent for GFP_NOWAIT, hence this check can't go wrong due to memalloc_no*_save/restore contexts. Willy is working on a patch series which might change this: https://lore.kernel.org/linux-mm/20200625113122.7540-7-willy@infradead.org/ I think best would be if that updates gfpflags_allow_blocking(), since there's a ton of callers all over the place for that already. Link: https://lkml.kernel.org/r/20201125162532.1299794-3-daniel.vetter@ffwll.ch Signed-off-by: Daniel Vetter Acked-by: Vlastimil Babka Acked-by: Paul E. McKenney Reviewed-by: Jason Gunthorpe Cc: Randy Dunlap Cc: Paul E. McKenney Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Vlastimil Babka Cc: Mathieu Desnoyers Cc: Sebastian Andrzej Siewior Cc: Michel Lespinasse Cc: Daniel Vetter Cc: Waiman Long Cc: Thomas Gleixner Cc: Randy Dunlap Cc: Dave Chinner Cc: Qian Cai Cc: "Matthew Wilcox (Oracle)" Cc: Christian König Cc: Ingo Molnar Cc: Jason Gunthorpe Cc: Maarten Lankhorst Cc: Thomas Hellström (Intel) Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched/mm.h | 16 ++++++++++++++++ mm/slab.h | 5 +---- mm/slob.c | 6 ++---- 3 files changed, 19 insertions(+), 8 deletions(-) diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index d5ece7a9a403..a11a61b5226f 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -180,6 +180,22 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { } static inline void fs_reclaim_release(gfp_t gfp_mask) { } #endif +/** + * might_alloc - Mark possible allocation sites + * @gfp_mask: gfp_t flags that would be used to allocate + * + * Similar to might_sleep() and other annotations, this can be used in functions + * that might allocate, but often don't. Compiles to nothing without + * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking. + */ +static inline void might_alloc(gfp_t gfp_mask) +{ + fs_reclaim_acquire(gfp_mask); + fs_reclaim_release(gfp_mask); + + might_sleep_if(gfpflags_allow_blocking(gfp_mask)); +} + /** * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope. * diff --git a/mm/slab.h b/mm/slab.h index 65f4647f1286..54faf9a623f9 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -510,10 +510,7 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, { flags &= gfp_allowed_mask; - fs_reclaim_acquire(flags); - fs_reclaim_release(flags); - - might_sleep_if(gfpflags_allow_blocking(flags)); + might_alloc(flags); if (should_failslab(s, flags)) return NULL; diff --git a/mm/slob.c b/mm/slob.c index 7cc9805c8091..8d4bfa46247f 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -474,8 +474,7 @@ __do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller) gfp &= gfp_allowed_mask; - fs_reclaim_acquire(gfp); - fs_reclaim_release(gfp); + might_alloc(gfp); if (size < PAGE_SIZE - minalign) { int align = minalign; @@ -597,8 +596,7 @@ static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node) flags &= gfp_allowed_mask; - fs_reclaim_acquire(flags); - fs_reclaim_release(flags); + might_alloc(flags); if (c->size < PAGE_SIZE) { b = slob_alloc(c->size, flags, c->align, node, 0);