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b=Jnh71ZnLqC9WXN3z6qJc1CKgt7N3C//7qq9exzhPmlknaIdEn2eHqQCs/RQppJeEx kZs6Iy/bADDiN+2S+0ayWEAuQeWUKZAVQUjRzFtLxhOpafXsq83uhpZJZsKQvfcXIo OlCtVmUQf5CD+vF+A9PoL0h3TEYWNGZAVPkksB6cgFwUfOu9a/ShxhTEnnsobZIh0F 3wkDHTfqTKHYLz9z30eVS/lWQZzGMSdX7tZeEBp2MeDh64kcyMSE14JZp0+S34fB2A CwGZwmuI32T3O+UC6MPw4rhPI7QeOIMCLymLmbOzC4OCTO9aDBFE8HFzc3ePOQCdqJ mKe7UI7PvEBLQ== X-Mailer: emacs 29.2 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Michal Hocko , "Huang, Ying" Cc: Andrew Morton , Donet Tom , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen , Mel Gorman , Ben Widawsky , Feng Tang , Andrea Arcangeli , Peter Zijlstra , Ingo Molnar , Rik van Riel , Johannes Weiner , Matthew Wilcox , Mike Kravetz , Vlastimil Babka , Dan Williams , Hugh Dickins , Kefeng Wang , Suren Baghdasaryan Subject: Re: [PATCH 1/3] mm/mempolicy: Use the already fetched local variable In-Reply-To: References: <9c3f7b743477560d1c5b12b8c111a584a2cc92ee.1708097962.git.donettom@linux.ibm.com> <20240218133851.22c22b55460e866a099be5ce@linux-foundation.org> <63a0f7c4-3c3f-4097-9a24-d1e3fc7b6030@linux.ibm.com> <20240219172130.82a16c1ebecbf8ba86a8987d@linux-foundation.org> <21f343fa-84a7-4539-91e2-6fc963dbfb62@kernel.org> <87frxnps8w.fsf@yhuang6-desk2.ccr.corp.intel.com> <7097ff95-6077-4744-a770-b90d224c0c9b@kernel.org> <8734tnppls.fsf@yhuang6-desk2.ccr.corp.intel.com> Date: Sun, 03 Mar 2024 11:47:47 +0530 Message-ID: <875xy3ltys.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: BE42E40005 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: qozxs3b9ng37wgch37sdwyp364o4q3ke X-HE-Tag: 1709446679-491771 X-HE-Meta: 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 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: Michal Hocko writes: > On Tue 20-02-24 15:22:07, Huang, Ying wrote: > [...] >> This isn't an issue now, because mpol_misplaced() are always called with >> PTL held. And, we can still keep thiscpu local variable. > > yes, this is the case but it would be better if we made that assumption > official by lockdep_assert_held > How about this folded into this patch? 2 files changed, 12 insertions(+), 4 deletions(-) mm/memory.c | 6 ++++-- mm/mempolicy.c | 10 ++++++++-- modified mm/memory.c @@ -4879,9 +4879,11 @@ static vm_fault_t do_fault(struct vm_fault *vmf) return ret; } -int numa_migrate_prep(struct folio *folio, struct vm_area_struct *vma, +int numa_migrate_prep(struct folio *folio, struct vm_fault *vmf, unsigned long addr, int page_nid, int *flags) { + struct vm_area_struct *vma = vmf->vma; + folio_get(folio); /* Record the current PID acceesing VMA */ @@ -4893,7 +4895,7 @@ int numa_migrate_prep(struct folio *folio, struct vm_area_struct *vma, *flags |= TNF_FAULT_LOCAL; } - return mpol_misplaced(folio, vma, addr); + return mpol_misplaced(folio, vmf, addr); } static vm_fault_t do_numa_page(struct vm_fault *vmf) modified mm/mempolicy.c @@ -2495,18 +2495,24 @@ static inline bool mpol_preferred_should_numa_migrate(int exec_node, int folio_n * Return: NUMA_NO_NODE if the page is in a node that is valid for this * policy, or a suitable node ID to allocate a replacement folio from. */ -int mpol_misplaced(struct folio *folio, struct vm_area_struct *vma, +int mpol_misplaced(struct folio *folio, struct vm_fault *vmf, unsigned long addr) { struct mempolicy *pol; pgoff_t ilx; struct zoneref *z; int curnid = folio_nid(folio); + struct vm_area_struct *vma = vmf->vma; int thiscpu = raw_smp_processor_id(); - int thisnid = cpu_to_node(thiscpu); + int thisnid = numa_node_id(); int polnid = NUMA_NO_NODE; int ret = NUMA_NO_NODE; + /* + * Make sure ptl is held so that we don't preempt and we + * have a stable smp processor id + */ + lockdep_assert_held(vmf->ptl); pol = get_vma_policy(vma, addr, folio_order(folio), &ilx); if (!(pol->flags & MPOL_F_MOF)) goto out; [back]