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Date: Mon, 20 Apr 2020 14:22:11 -0400 From: Daniel Jordan <daniel.m.jordan@...cle.com> To: Michel Lespinasse <walken@...gle.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>, Laurent Dufour <ldufour@...ux.ibm.com>, Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>, Liam Howlett <Liam.Howlett@...cle.com>, Jerome Glisse <jglisse@...hat.com>, Davidlohr Bueso <dave@...olabs.net>, David Rientjes <rientjes@...gle.com>, Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>, Jason Gunthorpe <jgg@...pe.ca>, Daniel Jordan <daniel.m.jordan@...cle.com> Subject: Re: [PATCH v4 07/10] mmap locking API: add mmap_read_trylock_non_owner() On Tue, Apr 14, 2020 at 05:43:50PM -0700, Michel Lespinasse wrote: > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 11d41f0c7005..998968659892 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -317,7 +316,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > * with build_id. > */ > if (!user || !current || !current->mm || irq_work_busy || > - mmap_read_trylock(current->mm) == 0) { > + !mmap_read_trylock_non_owner(current->mm)) { > /* cannot access current->mm, fall back to ips */ > for (i = 0; i < trace_nr; i++) { > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > @@ -342,16 +341,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > } > > if (!work) { > - mmap_read_unlock(current->mm); > + mmap_read_unlock_non_owner(current->mm); These 'non_owner' calls are not intuitive because current _is the owner, so the v3 version seems better, even if it adds a special wrapper for rwsem_release. Though it makes some sense if you think, "we're consistently using the non_owner APIs because there's a legitimate use somewhere else," so I'm fine either way. Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>
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