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To: Michal Hocko Cc: bpf , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Andrew Morton , Peter Zijlstra , Vlastimil Babka , Sebastian Sewior , Steven Rostedt , Hou Tao , Johannes Weiner , Shakeel Butt , Matthew Wilcox , Thomas Gleixner , Jann Horn , Tejun Heo , linux-mm , Kernel Team Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 9346F14000C X-Rspamd-Server: rspam12 X-Stat-Signature: 7wn4w6aa36g1u3zcrmeau96knrr4rn4x X-Rspam-User: X-HE-Tag: 1734711037-40886 X-HE-Meta: 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 j/41PPcH Y78EItWggDAsdDO7dhoMnXylFtD9zOGsLBWg8y39Qb5ZVBiKbxoxaze61/o0fVPgyVn/t7qm8v1ZehU0rzTkbtrtWrAsaOOKN7iKD2CK3C3oZ+ROgLh2zbGY3at6fOEDqI3/2GRygLz+yjH4SCTf1Ni8y5rQBdYaehO4mb5KjWhZ5wlI0mP0ZTrf2XXiB+cNdZeAcNPH3VUik8tDHDEOPKqQre3hpMfjdbLvzDL7DefXIc0iUjEMx7rUTUngt4SFso1UgSM1xE9OZcx4Wd81fZQm9xIbKOUOEOfjrWr3sFZ6XDuYV7EcFOykO5erxuISaIQbK7vPxRZwFOzaf8gyTn/MnfiprAIRqneKJaDOxKAdkDwVQkR+FUHdLE/PEafBVLB+Hwnx2mh20yW+1wT6WPKsafCxRjlzIg3zYf7BTKUpXcFbRMeiLXrknojhuWbUnGo/GFLmTcRQ+i3g= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Dec 20, 2024 at 12:24=E2=80=AFAM Michal Hocko wro= te: > > > +static inline bool gfpflags_allow_spinning(const gfp_t gfp_flags) > > +{ > > + /* > > + * !__GFP_DIRECT_RECLAIM -> direct claim is not allowed. > > + * !__GFP_KSWAPD_RECLAIM -> it's not safe to wake up kswapd. > > + * All GFP_* flags including GFP_NOWAIT use one or both flags. > > + * try_alloc_pages() is the only API that doesn't specify eithe= r flag. > > I wouldn't be surprised if we had other allocations like that. git grep > is generally not very helpful as many/most allocations use gfp argument > of a sort. I would slightly reword this to be more explicit. > /* > * This is stronger than GFP_NOWAIT or GFP_ATOMIC because > * those are guaranteed to never block on a sleeping lock. > * Here we are enforcing that the allaaction doesn't ever spin > * on any locks (i.e. only trylocks). There is no highlevel > * GFP_$FOO flag for this use try_alloc_pages as the > * regular page allocator doesn't fully support this > * allocation mode. Makes sense. I like this new wording. Will incorporate. > > + */ > > + return !(gfp_flags & __GFP_RECLAIM); > > +} > > + > > #ifdef CONFIG_HIGHMEM > > #define OPT_ZONE_HIGHMEM ZONE_HIGHMEM > > #else > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index f168d223375f..545d345c22de 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -1768,7 +1768,7 @@ static bool consume_stock(struct mem_cgroup > > *memcg, unsigned int nr_pages, > > return ret; > > > > if (!local_trylock_irqsave(&memcg_stock.stock_lock, flags)) { > > - if (gfp_mask & __GFP_TRYLOCK) > > + if (!gfpflags_allow_spinning(gfp_mask)) > > return ret; > > local_lock_irqsave(&memcg_stock.stock_lock, flags); > > } > > > > If that's acceptable then such an approach will work for > > my slub.c reentrance changes too. > > It certainly is acceptable for me. Great. > Do not forget to add another hunk to > avoid charging the full batch in this case. Well. It looks like you spotted the existing bug ? Instead of + if (!gfpflags_allow_blockingk(gfp_mask)) + batch =3D nr_pages; it should be unconditional: + batch =3D nr_pages; after consume_stock() returns false. Consider: stock_pages =3D READ_ONCE(stock->nr_pages); if (memcg =3D=3D READ_ONCE(stock->cached) && stock_pages >=3D nr_pa= ges) { stock_pages =3D=3D 10 nr_pages =3D=3D 20 so after consume_stock() returns false the batch will stay =3D=3D MEMCG_CHARGE_BATCH =3D=3D 64 and page_counter_try_charge(&memcg->memsw, batch,... will charge too much ? and the bug was there for a long time. Johaness, looks like it's mostly your code? Pls help us out.