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[122.222.156.169]) by smtp.gmail.com with ESMTPSA id q207-v6sm7409500pgq.11.2018.06.21.19.15.19 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 21 Jun 2018 19:15:21 -0700 (PDT) Date: Fri, 22 Jun 2018 12:15:11 +1000 From: Nicholas Piggin To: Matthew Wilcox Cc: linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , "Aneesh Kumar K.V" , Thiago Jung Bauermann , Ram Pai , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 13/26] ppc: Convert mmu context allocation to new IDA API Message-ID: <20180622121511.00ae9d00@roar.ozlabs.ibm.com> In-Reply-To: <20180621212835.5636-14-willy@infradead.org> References: <20180621212835.5636-1-willy@infradead.org> <20180621212835.5636-14-willy@infradead.org> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Jun 2018 14:28:22 -0700 Matthew Wilcox wrote: > ida_alloc_range is the perfect fit for this use case. Eliminates > a custom spinlock, a call to ida_pre_get and a local check for the > allocated ID exceeding a maximum. > > Signed-off-by: Matthew Wilcox > --- > arch/powerpc/mm/mmu_context_book3s64.c | 44 +++----------------------- > 1 file changed, 4 insertions(+), 40 deletions(-) > > diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c > index f3d4b4a0e561..5a0cf2cc8ba0 100644 > --- a/arch/powerpc/mm/mmu_context_book3s64.c > +++ b/arch/powerpc/mm/mmu_context_book3s64.c > @@ -26,48 +26,16 @@ > #include > #include > > -static DEFINE_SPINLOCK(mmu_context_lock); > static DEFINE_IDA(mmu_context_ida); > > static int alloc_context_id(int min_id, int max_id) > { > - int index, err; > - > -again: > - if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL)) > - return -ENOMEM; > - > - spin_lock(&mmu_context_lock); > - err = ida_get_new_above(&mmu_context_ida, min_id, &index); > - spin_unlock(&mmu_context_lock); > - > - if (err == -EAGAIN) > - goto again; > - else if (err) > - return err; > - > - if (index > max_id) { > - spin_lock(&mmu_context_lock); > - ida_remove(&mmu_context_ida, index); > - spin_unlock(&mmu_context_lock); > - return -ENOMEM; > - } > - > - return index; > + return ida_alloc_range(&mmu_context_ida, min_id, max_id, GFP_KERNEL); > } > > void hash__reserve_context_id(int id) > { > - int rc, result = 0; > - > - do { > - if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL)) > - break; > - > - spin_lock(&mmu_context_lock); > - rc = ida_get_new_above(&mmu_context_ida, id, &result); > - spin_unlock(&mmu_context_lock); > - } while (rc == -EAGAIN); > + int result = ida_alloc_range(&mmu_context_ida, id, id, GFP_KERNEL); > > WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result); > } > @@ -172,9 +140,7 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm) > > void __destroy_context(int context_id) > { > - spin_lock(&mmu_context_lock); > - ida_remove(&mmu_context_ida, context_id); > - spin_unlock(&mmu_context_lock); > + ida_free(&mmu_context_ida, context_id); > } > EXPORT_SYMBOL_GPL(__destroy_context); > > @@ -182,13 +148,11 @@ static void destroy_contexts(mm_context_t *ctx) > { > int index, context_id; > > - spin_lock(&mmu_context_lock); > for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) { > context_id = ctx->extended_id[index]; > if (context_id) > - ida_remove(&mmu_context_ida, context_id); > + ida_free(&mmu_context_ida, context_id); > } > - spin_unlock(&mmu_context_lock); > } > > static void pte_frag_destroy(void *pte_frag) This hunk should be okay because the mmu_context_lock does not protect the extended_id array, right Aneesh? Reviewed-by: Nicholas Piggin Thanks, Nick