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Sat, 11 Apr 2026 21:39:48 -0700 (PDT) Received: from fedora ([2601:644:937c:6c90::f8b0]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2d561bde70csm13449412eec.15.2026.04.11.21.39.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Apr 2026 21:39:48 -0700 (PDT) Date: Sat, 11 Apr 2026 21:39:45 -0700 From: Vishal Moola To: Matthew Brost Cc: intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, David Hildenbrand , Oscar Salvador , Andrew Morton , Balbir Singh , linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/zone_device: Do not touch device folio after calling ->folio_free() Message-ID: References: <20260410230346.4009855-1-matthew.brost@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260410230346.4009855-1-matthew.brost@intel.com> X-Rspamd-Queue-Id: 20D8580008 X-Stat-Signature: wzah565otg8ia9ixwtr5zisop7hs96h9 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1775968789-518007 X-HE-Meta: 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 W44ychAk 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 10, 2026 at 04:03:46PM -0700, Matthew Brost wrote: > The contents of a device folio can immediately change after calling > ->folio_free(), as the folio may be reallocated by a driver with a > different order. Instead of touching the folio again to extract the > pgmap, use the local stack variable when calling percpu_ref_put_many(). > > Cc: David Hildenbrand > Cc: Oscar Salvador > Cc: Andrew Morton > Cc: Balbir Singh > Cc: linux-mm@kvack.org > Cc: linux-cxl@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Fixes: d245f9b4ab80 ("mm/zone_device: support large zone device private folios") > Signed-off-by: Matthew Brost With the cc-stable: Reviewed-by: Vishal Moola > --- > Stack trace: > > [ 631.875165] [IGT] xe_exec_system_allocator: starting subtest threads-many-new-prefetch > [ 632.282992] Oops: general protection fault, probably for non-canonical address 0x900000000000000: 0000 [#1] SMP NOPTI > [ 632.293469] CPU: 8 UID: 0 PID: 59267 Comm: xe_exec_system_ Not tainted 7.0.0-rc7-xe+ #281 PREEMPT(full) > [ 632.316023] RIP: 0010:free_zone_device_folio+0x149/0x240 > [ 632.339782] RSP: 0000:ffffc90023d1fd00 EFLAGS: 00010206 > [ 632.344947] RAX: 0900000000000000 RBX: 0000000000000001 RCX: 0000000094472d4d > [ 632.351991] RDX: ffffffff8155c76f RSI: 000000006f2213bf RDI: 000000008e84943a > [ 632.359042] RBP: ffffea0ff4030001 R08: 0000000000000000 R09: 0000000000000001 > [ 632.366094] R10: 0000000000000028 R11: 0000000000000000 R12: ffff88811828e400 > [ 632.373145] R13: 0000000000000000 R14: 000fffffc0000000 R15: 0000000000100073 > [ 632.380194] FS: 00007f2f0fdfe6c0(0000) GS:ffff88890a7e7000(0000) knlGS:0000000000000000 > [ 632.388186] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 632.393870] CR2: 00007f2f002e90f8 CR3: 0000000106708002 CR4: 0000000000f70ef0 > [ 632.400919] PKRU: 55555554 > [ 632.403605] Call Trace: > [ 632.406039] > [ 632.408131] do_swap_page+0x146d/0x18c0 > [ 632.411938] ? __pte_offset_map+0x3e/0x190 > [ 632.415994] __handle_mm_fault+0x6e8/0x8d0 > [ 632.420053] handle_mm_fault+0xbf/0x250 > [ 632.423855] ? lock_mm_and_find_vma+0x41/0x6f0 > [ 632.428256] do_user_addr_fault+0x168/0x690 > [ 632.432399] exc_page_fault+0x74/0x200 > [ 632.436117] asm_exc_page_fault+0x26/0x30 > [ 632.440092] RIP: 0033:0x5587554ff70d > [ 632.462142] RSP: 002b:00007f2f0fdfc970 EFLAGS: 00010246 > [ 632.467308] RAX: 0000000000003fc0 RBX: 00007f2f082e1fc0 RCX: 00007f2f12b3287d > [ 632.474355] RDX: 0000000000000000 RSI: 00000000c048644a RDI: 0000000000000003 > [ 632.481404] RBP: 00007f2f082e1fc0 R08: 00007f2f0fdfc958 R09: 0000000000000066 > [ 632.488450] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 > [ 632.495495] R13: 00007f2f082de000 R14: 0000000000c00002 R15: 00007f2f1319e000 > [ 632.502547] > --- > mm/memremap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memremap.c b/mm/memremap.c > index ac7be07e3361..053842d45cb1 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -454,7 +454,7 @@ void free_zone_device_folio(struct folio *folio) > if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->folio_free)) > break; > pgmap->ops->folio_free(folio); > - percpu_ref_put_many(&folio->pgmap->ref, nr); > + percpu_ref_put_many(&pgmap->ref, nr); > break; > > case MEMORY_DEVICE_GENERIC: > -- > 2.34.1 >