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/[email protected]/
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 <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Cc. Randy Dunlap <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Dave Chinner <[email protected]>
Cc: Qian Cai <[email protected]>
Cc: [email protected]
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
---
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);
--
2.29.2