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b=OkoG1IKEfI+0ioKSLycirL/K1vFKFCP9Mg+mXh/2NPhjfxSYxkscRC224VhUrpqlm ut39oY5YVyCTDXOETHlGj/s8vDmquE7/5fhe6KgMqKV6ZvSo5iypocWzgCLhrgLOtq kzv/6mCiBEGDyRknt1D+c2vGg2bza38eJ44Jqt1I= Date: Mon, 22 Apr 2024 14:28:35 -0700 From: Andrew Morton To: Hariom Panthi Cc: urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, maninder1.s@samsung.com, r.thapliyal@samsung.com Subject: Re: [PATCH 1/1] mm: vmalloc: dump page owner info if page is already mapped Message-Id: <20240422142835.3a2fe7740dfc3003b68de305@linux-foundation.org> In-Reply-To: <20240419043910.2156379-1-hariom1.p@samsung.com> References: <20240419043910.2156379-1-hariom1.p@samsung.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 072E7A0011 X-Stat-Signature: 5qing7p17ngj5ycqhed3y1epjrnjd678 X-HE-Tag: 1713821320-729417 X-HE-Meta: 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 sOhDKWF6 osLOR0oS3toLTPSCF63PHQ3HKRnCMc7z3SXEdNReLAHwQePEAlSn6XWhM8HbOlfHnlxYJNPh/XvtyEiYmOCJUcOO6IppQ5E9GrRcPRz3leAzomQy2PBR+Jl9xuN94pYbAe/W6HBCaF4H3ctV7R8/P7w1eIxCROp59MtjqV/7FiZEJXlom3A8fjU1C1voN8zIxiQDNx/MgcAlPq9lspsXp5BLJJSy1AFOp28mpjbtorsizdcok0btGneKKnA== 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: On Fri, 19 Apr 2024 10:09:10 +0530 Hariom Panthi wrote: > In vmap_pte_range, BUG_ON is called when page is already mapped, > It doesn't give enough information to debug further. > Dumping page owner information alongwith BUG_ON will be more useful > in case of multiple page mapping. > > Example: > [ 18.258806] page_owner tracks the page as allocated > [ 18.258970] page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL), pid 81, tgid 81 (insmod), ts 18257811008, free_ts 0 > [ 18.259327] prep_new_page+0xa8/0x10c > [ 18.259455] get_page_from_freelist+0x7f8/0x1248 > [ 18.259591] __alloc_pages+0x164/0x2b4 > [ 18.259703] alloc_pages_mpol+0x88/0x230 > [ 18.259821] alloc_pages+0x4c/0x7c > [ 18.259923] load_module+0x74/0x1af4 > [ 18.260031] __do_sys_init_module+0x190/0x1fc > [ 18.260154] __arm64_sys_init_module+0x1c/0x28 > [ 18.260280] invoke_syscall+0x44/0x108 > [ 18.260394] el0_svc_common.constprop.0+0x40/0xe0 > [ 18.260530] do_el0_svc_compat+0x1c/0x34 > [ 18.260647] el0_svc_compat+0x2c/0x80 > [ 18.260761] el0t_32_sync_handler+0x90/0x140 > [ 18.260887] el0t_32_sync+0x194/0x198 > [ 18.260996] page_owner free stack trace missing > [ 18.261143] ------------[ cut here ]------------ > [ 18.261272] kernel BUG at mm/vmalloc.c:113! > > ... > > @@ -103,7 +105,13 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > if (!pte) > return -ENOMEM; > do { > - BUG_ON(!pte_none(ptep_get(pte))); > + if (!pte_none(ptep_get(pte))) { > + if (pfn_valid(pfn)) { > + page = pfn_to_page(pfn); > + dump_page_owner(page); > + } > + BUG(); > + } Diving straight into dump_page_owner() seems inappropriate. The higher-level dump_page() interface is more typically used. Or, even more common, VM_BUG_ON_PAGE(), but that doesn't look to be a good fit here.