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bh=xHOYFA6euJfasLOVVDPvM+vmyipK/73yYjmFYAFFKE0=; b=PDwxfEmInVHV2rxzfi4EKK4xk/ft4DyWznUcKUX7t1p+03s5dYu9W2AcZ4f5nukZJEL1Zm Hq1Y+EyDkI+GG02N3uHS6RJ3D64hMVQ+zonLRO47w8a8wtU/oVsdBpJRV2qxD5gQ/OKEso kQxxVYJK+6gHXVaUiG9Hk5LlaYbW36rvC+lZCgcgb8TzDoRGE87O24L+PlcLjWaYaF+e7/ 2nY5E/tbh5O7+7CKO8ZBL4MkvVL7f1xplGAxT5T+L877FVUMk45qFpvpH84QfLeySPweOr j7fKSCZKtXK96mlpjg+ad+Z0VRLliX6rF1MeJ+LW/4ksfaOGZzFk/Egd4WZIsA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1684938912; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xHOYFA6euJfasLOVVDPvM+vmyipK/73yYjmFYAFFKE0=; b=0gSCGJ9DlPSlWoBQp5BrR7+U9RLX3mBJsmUUmGR/KsrKrMPHoOmvoHI/R9zr/kmv/KqKc0 F14Z7V8rirzOwzBQ== To: Baoquan He Cc: linux-mm@kvack.org, Andrew Morton , Christoph Hellwig , Uladzislau Rezki , Lorenzo Stoakes , Peter Zijlstra Subject: Re: [patch 1/6] mm/vmalloc: Prevent stale TLBs in fully utilized blocks In-Reply-To: References: <20230523135902.517032811@linutronix.de> <20230523140002.575854344@linutronix.de> <87jzwym4yr.ffs@tglx> Date: Wed, 24 May 2023 16:35:11 +0200 Message-ID: <874jo1n6g0.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2C872180012 X-Stat-Signature: o3shzdsdioa7rwpsu35ijofnu4yhn419 X-HE-Tag: 1684938913-427726 X-HE-Meta: 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 1TvBE/65 eS0aJmtEfm+VJ7EtFjceycizI9j4qApACxVUuHjNwlfNxLIQ= 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: On Wed, May 24 2023 at 22:10, Baoquan He wrote: > On 05/24/23 at 11:52am, Thomas Gleixner wrote: >> On Wed, May 24 2023 at 17:32, Baoquan He wrote: >> > On 05/23/23 at 04:02pm, Thomas Gleixner wrote: >> >> @@ -2236,9 +2236,10 @@ static void _vm_unmap_aliases(unsigned l >> >> for_each_possible_cpu(cpu) { >> >> struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu); >> >> struct vmap_block *vb; >> >> + unsigned long idx; >> >> >> >> rcu_read_lock(); >> > >> > Do we need to remove this rcu_read_xx() pair since it marks the RCU >> > read-side critical section on vbq-free list? >> >> And what protects the xarray lookup? > > We have put rcu_read_lock() pair around the xas_find(). And it will find > into xarray for each iteration item. We won't lose the connection to the > next element like list adding or deleting? not very sure, I could be > wrong. > > xa_for_each() > -->xa_for_each_start() > -->xa_for_each_range() > -->xa_find() I know how xarray works. No need to copy the code. rcu_read_lock() inside xa_find() protects the search, but it does not protect the returned entry, which might go away right after xa_find() does rcu_read_unlock(). Thanks, tglx