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.
v2: Fix typos in kerneldoc (Randy)
Acked-by: Vlastimil Babka vbabka@suse.cz Acked-by: Paul E. McKenney paulmck@kernel.org Reviewed-by: Jason Gunthorpe jgg@nvidia.com Cc. Randy Dunlap rdunlap@infradead.org Cc: Paul E. McKenney paulmck@kernel.org Cc: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Ingo Molnar mingo@kernel.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Sebastian Andrzej Siewior bigeasy@linutronix.de Cc: Michel Lespinasse walken@google.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Waiman Long longman@redhat.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Randy Dunlap rdunlap@infradead.org Cc: linux-mm@kvack.org Cc: linux-fsdevel@vger.kernel.org Cc: Dave Chinner david@fromorbit.com Cc: Qian Cai cai@lca.pw Cc: linux-xfs@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" willy@infradead.org Signed-off-by: Daniel Vetter daniel.vetter@intel.com --- 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 6d7c6a5056ba..37b981247e5d 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -500,10 +500,7 @@ 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);