On Tue 26-03-19 20:59:48, Qian Cai wrote: [...] > Unless there is a brave soul to reimplement the kmemleak to embed it's > metadata into the tracked memory itself in a foreseeable future, this > provides a good balance between enabling kmemleak in a low-memory > situation and not introducing too much hackiness into the existing > code for now. Another approach is to fail back the original allocation > once kmemleak_alloc() failed, but there are too many call sites to > deal with which makes it error-prone. As long as there is an implicit __GFP_NOFAIL then kmemleak is simply broken no matter what other gfp flags you play with. Has anybody looked at some sort of preallocation where gfpflags_allow_blocking context allocate objects into a pool that non-sleeping allocations can eat from? > kmemleak: Cannot allocate a kmemleak_object structure > kmemleak: Kernel memory leak detector disabled > kmemleak: Automatic memory scanning thread ended > RIP: 0010:__alloc_pages_nodemask+0x242a/0x2ab0 > Call Trace: > allocate_slab+0x4d9/0x930 > new_slab+0x46/0x70 > ___slab_alloc+0x5d3/0x9c0 > __slab_alloc+0x12/0x20 > kmem_cache_alloc+0x30a/0x360 > create_object+0x96/0x9a0 > kmemleak_alloc+0x71/0xa0 > kmem_cache_alloc+0x254/0x360 > mempool_alloc_slab+0x3f/0x60 > mempool_alloc+0x120/0x329 > bio_alloc_bioset+0x1a8/0x510 > get_swap_bio+0x107/0x470 > __swap_writepage+0xab4/0x1650 > swap_writepage+0x86/0xe0 > > Signed-off-by: Qian Cai <cai@xxxxxx> > --- > > v4: Update the commit log. > Fix a typo in comments per Christ. > Consolidate the allocation. > v3: Update the commit log. > Simplify the code inspired by graph_trace_open() from ftrace. > v2: Remove the needless checking for NULL objects in slab_post_alloc_hook() > per Catalin. > > mm/kmemleak.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index a2d894d3de07..7f4545ab1f84 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -580,7 +580,16 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, > struct rb_node **link, *rb_parent; > unsigned long untagged_ptr; > > - object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp)); > + /* > + * The tracked memory was allocated successful, if the kmemleak object > + * failed to allocate for some reasons, it ends up with the whole > + * kmemleak disabled, so try it harder. > + */ > + gfp = (in_atomic() || irqs_disabled()) ? > + gfp_kmemleak_mask(gfp) | GFP_ATOMIC : > + gfp_kmemleak_mask(gfp) | __GFP_DIRECT_RECLAIM; The comment for in_atomic says: * Are we running in atomic context? WARNING: this macro cannot * always detect atomic context; in particular, it cannot know about * held spinlocks in non-preemptible kernels. Thus it should not be * used in the general case to determine whether sleeping is possible. * Do not use in_atomic() in driver code. -- Michal Hocko SUSE Labs
