From nobody Thu Oct 2 23:48:29 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA62833EB12; Tue, 9 Sep 2025 12:42:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757421769; cv=none; b=C+roZeinYzmcrPvWRGhv/pkgTiU4eJ29OTp4oItPh2/KtwRd88ICvJr7orw1TCPe0ojOEZcUHsZBLmk0sI2KLBvwdkDD/m24mqWCYLLe5zUzPnuyrzwImY2tBZfbHx3jdzLEkl0L6wEWp9+3wt3ODQ2NDcy8H3B+71LTxuaQdw0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757421769; c=relaxed/simple; bh=Pt6R1lXQxECu96oquYdgEIA0VrhXv/RzniYpUbGqgSI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BfSvBPLZcjKrFofMzvHnsxnSQMbuoQEATGoYUnFMfnPuxSp8rez1gvXMPIlouhiIXhgR2LzfRjHH58QAe+a8ckkfJZVcq1sjaEnXycC3upwvOY2x3DktKmfoL2hWUVlepkWSK3dmpRQem0XTFwTewf3VF5xl6M11aZ5Uj0qYr78= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=edZhkqCg; arc=none smtp.client-ip=192.198.163.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="edZhkqCg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1757421768; x=1788957768; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Pt6R1lXQxECu96oquYdgEIA0VrhXv/RzniYpUbGqgSI=; b=edZhkqCgIGwrMRURj45eT/Vlax5qHr/z3Y5bu1BApbRSoeWt+N2kx3i0 yTlQ+WTc5coGb5kZDFw4CwzilgnVKC5Mllh+Ht0lNkIIXtSnYkVWg4WFk u4YyCfGcl1wwG2EWPg1R9qDVxj2xa1LqZ5O3ISFPutfRHna99FllhkBw2 tl3qzkPM9JksxrFwJnzB8ZSaB2x3C9uDpABj3UC0ljkNkI8+kpOgCM+8B b+QfI4358wLBIR1ERALyMvM7W1ys/133hxGX+Fn82G4y1KQb0DOoGiJdA u3fQ93WkflEOHII4qm207/QvB7PBs9kxdKw/qE3vUvNoRF0JnO7lv1omC w==; X-CSE-ConnectionGUID: rH2CTtoTSt2oQYL43tHPZA== X-CSE-MsgGUID: rEpL8Fb2S++G/TkNCk70ew== X-IronPort-AV: E=McAfee;i="6800,10657,11547"; a="70399573" X-IronPort-AV: E=Sophos;i="6.18,251,1751266800"; d="scan'208";a="70399573" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2025 05:42:48 -0700 X-CSE-ConnectionGUID: uGyzRG44TECZQRgYsqdZqg== X-CSE-MsgGUID: K7rh66MDRg2kow9aXEBTTw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,251,1751266800"; d="scan'208";a="172667483" Received: from abityuts-desk.ger.corp.intel.com (HELO localhost.localdomain) ([10.245.244.84]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2025 05:42:43 -0700 From: Adrian Hunter To: Peter Zijlstra Cc: Ingo Molnar , Alexander Shishkin , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Mark Rutland , Ian Rogers , Kan Liang , Mathieu Poirier , Miklos Szeredi , Alexander Viro , Christian Brauner , Amir Goldstein , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH 3/3] perf/core: Fix MMAP2 event device with backing files Date: Tue, 9 Sep 2025 15:42:22 +0300 Message-ID: <20250909124222.222945-4-adrian.hunter@intel.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250909124222.222945-1-adrian.hunter@intel.com> References: <20250909124222.222945-1-adrian.hunter@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Organization: Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Some file systems like FUSE-based ones or overlayfs may record the backing file in struct vm_area_struct vm_file, instead of the user file that the user mmapped. That causes perf to misreport the device major/minor numbers of the file system of the file, and the generation of the file, and potentially other inode details. There is an existing helper file_user_inode() for that situation. Use file_user_inode() instead of file_inode() to get the inode for MMAP2 events. Example: Setup: # cd /root # mkdir test ; cd test ; mkdir lower upper work merged # cp `which cat` lower # mount -t overlay overlay -olowerdir=3Dlower,upperdir=3Dupper,workdir= =3Dwork merged # perf record -e cycles:u -- /root/test/merged/cat /proc/self/maps ... 55b2c91d0000-55b2c926b000 r-xp 00018000 00:1a 3419 = /root/test/merged/cat ... [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.004 MB perf.data (5 samples) ] # # stat /root/test/merged/cat File: /root/test/merged/cat Size: 1127792 Blocks: 2208 IO Block: 4096 regular file Device: 0,26 Inode: 3419 Links: 1 Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2025-09-08 12:23:59.453309624 +0000 Modify: 2025-09-08 12:23:59.454309624 +0000 Change: 2025-09-08 12:23:59.454309624 +0000 Birth: 2025-09-08 12:23:59.453309624 +0000 Before: Device reported 00:02 differs from stat output and /proc/self/maps # perf script --show-mmap-events | grep /root/test/merged/cat cat 377 [-01] 243.078558: PERF_RECORD_MMAP2 377/377: [0x= 55b2c91d0000(0x9b000) @ 0x18000 00:02 3419 2068525940]: r-xp /root/test/mer= ged/cat After: Device reported 00:1a is the same as stat output and /proc/self/maps # perf script --show-mmap-events | grep /root/test/merged/cat cat 362 [-01] 127.755167: PERF_RECORD_MMAP2 362/362: [0x= 55ba6e781000(0x9b000) @ 0x18000 00:1a 3419 0]: r-xp /root/test/merged/cat With respect to stable kernels, overlayfs mmap function ovl_mmap() was added in v4.19 but file_user_inode() was not added until v6.8 and never back-ported to stable kernels. FMODE_BACKING that it depends on was added in v6.5. This issue has gone largely unnoticed, so back-porting before v6.8 is probably not worth it, so put 6.8 as the stable kernel prerequisite version, although in practice the next long term kernel is 6.12. Cc: stable@vger.kernel.org # 6.8 Signed-off-by: Adrian Hunter Acked-by: Amir Goldstein --- kernel/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index e203b8d90fd2..9d281785b99e 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9403,7 +9403,7 @@ static void perf_event_mmap_event(struct perf_mmap_ev= ent *mmap_event) flags |=3D MAP_HUGETLB; =20 if (file) { - struct inode *inode; + const struct inode *inode; dev_t dev; =20 buf =3D kmalloc(PATH_MAX, GFP_KERNEL); @@ -9421,7 +9421,7 @@ static void perf_event_mmap_event(struct perf_mmap_ev= ent *mmap_event) name =3D "//toolong"; goto cpy_name; } - inode =3D file_inode(vma->vm_file); + inode =3D file_user_inode(vma->vm_file); dev =3D inode->i_sb->s_dev; ino =3D inode->i_ino; gen =3D inode->i_generation; --=20 2.48.1