From patchwork Wed Aug 28 10:19:41 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aleksa Sarai X-Patchwork-Id: 13781062 Received: from mout-p-201.mailbox.org (mout-p-201.mailbox.org [80.241.56.171]) (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 AF72B158DCD; Wed, 28 Aug 2024 10:20:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724840418; cv=none; b=lQ+I5FIWSNJfQEcM5nWKCfSKxAIAY/AusZsdS8WN2LsalCtXk7z20+Gx5Di6KVuUoOTIvy9jPnv8UHhcDL1Qck/rQEhkyqqmjFd4cn8/tKEudiSDPB4sDZCirI3hHxFD8Nzv67hGNhDa5+WzDXtDLT1M7i/KchlFsPeXMgd4J4c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724840418; c=relaxed/simple; bh=59C1j5eCmqZob8jEIShtx6eoNd5luED/6NCiA7rxG+U=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=ulnHC68ayMrgB9HkuMxhK8+HVkLErV7CstwDLA1KA0wHMPCEYPB0+q3pdBIenvWXJV5wwqAAMSxaRvK/g0++CTqKeS/V6GUA8FWWQW+XVQH9ILtF9bPM7yyZgEkaeJBoRUM0Dd+9HKqpWx5MRs6DnVJca0ElXW7I5beiHGTI+q8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com; spf=pass smtp.mailfrom=cyphar.com; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b=HVmx42q7; arc=none smtp.client-ip=80.241.56.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cyphar.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b="HVmx42q7" Received: from smtp202.mailbox.org (smtp202.mailbox.org [10.196.197.202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-201.mailbox.org (Postfix) with ESMTPS id 4Wv0ln3Jsfz9sm9; Wed, 28 Aug 2024 12:20:05 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1724840405; 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: content-transfer-encoding:content-transfer-encoding; bh=lAXYyraN7ZXI7ooTWwWvHdZefjdmGcmzLAz3G34pbEg=; b=HVmx42q7LKdSUqNjcYJckrDgSJg/vx4YHLXt/MyMJDnWK1lrauhvMKWsTVwfHIirTFsZ+G oYALAAWMGq+0EINNslOHWu9jFLK+xq5iwNyp7mzDrI3xF8tqP/rK6dmabAk4FzGm+ZLqTQ t/rEnlKpBBCg5LSg7S9+GUPDZC4Lhj3tvFjVm8QOzRkFtl4nVi9P2D80qBBTbaaHIOm9Xh s+rAEEcUevtnEk6jl/F1HPGfRArblLbjl8Ho5QB4FxY9DtQ/JaaBw8U99yk5U7/9E1otqR SFYS6urnNvWaIYcBTZPElQJ2jFk6rtZiamOXcRzcYNIkrzP8P23uH6FyEx2uhg== From: Aleksa Sarai Subject: [PATCH RESEND v3 0/2] fhandle: expose u64 mount id to name_to_handle_at(2) Date: Wed, 28 Aug 2024 20:19:41 +1000 Message-Id: <20240828-exportfs-u64-mount-id-v3-0-10c2c4c16708@cyphar.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAL35zmYC/3XNsU7DMBAG4FepPHPIZ+dK3KlDuzLQETHEzpl4a BzZadSqyrvXhAEQyvjf/ffdXWROgbPYbe4i8RRyiH0J+mkjXNf0nwyhLVkoqSpJSMDXIabRZ7h sKzjHSz+WBhi2lhzVlrQT5XZI7MN1cd/F2/F0fD2IjzLvQh5jui3vJly237KSK/KEgOCJfGsUk q15725D16RnF88LOanfjF5j1BdjvCHj8YUt/mP0D1NLXGM0SLBM7VbVGquq+cPM8/wA7MPBIVE BAAA= To: Alexander Viro , Christian Brauner , Jan Kara , Chuck Lever , Jeff Layton , Amir Goldstein , Alexander Aring , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter Cc: Christoph Hellwig , Josef Bacik , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-perf-users@vger.kernel.org, Aleksa Sarai X-Developer-Signature: v=1; a=openpgp-sha256; l=2969; i=cyphar@cyphar.com; h=from:subject:message-id; bh=59C1j5eCmqZob8jEIShtx6eoNd5luED/6NCiA7rxG+U=; b=owGbwMvMwCWmMf3Xpe0vXfIZT6slMaSd+3l8x1UdNqsKTZbNB3u0nFKzLPpXRGT+uHr4aOp35 dVxKlFPOkpZGMS4GGTFFFm2+XmGbpq/+Eryp5VsMHNYmUCGMHBxCsBE3MUYGTYveS5THVbU//Ll T/m17IKKMwO57rBe05Gx39TwwsQxJY/hn6LHwbNVES7HFrfuCm47db1F9Vb0P/6XcxWPR74wfel yjAEA X-Developer-Key: i=cyphar@cyphar.com; a=openpgp; fpr=C9C370B246B09F6DBCFC744C34401015D1D2D386 Now that we provide a unique 64-bit mount ID interface in statx(2), we can now provide a race-free way for name_to_handle_at(2) to provide a file handle and corresponding mount without needing to worry about racing with /proc/mountinfo parsing or having to open a file just to do statx(2). While this is not necessary if you are using AT_EMPTY_PATH and don't care about an extra statx(2) call, users that pass full paths into name_to_handle_at(2) need to know which mount the file handle comes from (to make sure they don't try to open_by_handle_at a file handle from a different filesystem) and switching to AT_EMPTY_PATH would require allocating a file for every name_to_handle_at(2) call, turning err = name_to_handle_at(-EBADF, "/foo/bar/baz", &handle, &mntid, AT_HANDLE_MNT_ID_UNIQUE); into int fd = openat(-EBADF, "/foo/bar/baz", O_PATH | O_CLOEXEC); err1 = name_to_handle_at(fd, "", &handle, &unused_mntid, AT_EMPTY_PATH); err2 = statx(fd, "", AT_EMPTY_PATH, STATX_MNT_ID_UNIQUE, &statxbuf); mntid = statxbuf.stx_mnt_id; close(fd); Also, this series adds a patch to clarify how AT_* flag allocation should work going forwards. Signed-off-by: Aleksa Sarai --- Resend: - v3: Changes in v3: - Added a patch describing how AT_* flags should be allocated in the future, based on Amir's suggestions. - Included AT_* aliases for RENAME_* flags to further indicate that renameat2(2) is an *at(2) syscall and to indicate that those flags have been allocated already in the per-syscall range. - Switched AT_HANDLE_MNT_ID_UNIQUE to use 0x01 (to reuse (AT_)RENAME_NOREPLACE). - v2: Changes in v2: - Fixed a few minor compiler warnings and a buggy copy_to_user() check. - Rename AT_HANDLE_UNIQUE_MOUNT_ID -> AT_HANDLE_MNT_ID_UNIQUE to match statx. - Switched to using an AT_* bit from 0xFF and defining that range as being "per-syscall" for future usage. - Sync tools/ copy of to include changes. - v1: --- Aleksa Sarai (2): uapi: explain how per-syscall AT_* flags should be allocated fhandle: expose u64 mount id to name_to_handle_at(2) fs/fhandle.c | 29 ++++++-- include/linux/syscalls.h | 2 +- include/uapi/linux/fcntl.h | 81 ++++++++++++++------- tools/perf/trace/beauty/include/uapi/linux/fcntl.h | 84 +++++++++++++++------- 4 files changed, 140 insertions(+), 56 deletions(-) --- base-commit: 766508e7e2c5075eb744cb29b8cef6fa835b0344 change-id: 20240515-exportfs-u64-mount-id-9ebb5c58b53c Best regards,