From patchwork Thu Aug 1 03:52:39 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aleksa Sarai X-Patchwork-Id: 13749516 Received: from mout-p-102.mailbox.org (mout-p-102.mailbox.org [80.241.56.152]) (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 4242413958F; Thu, 1 Aug 2024 03:53:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.152 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722484384; cv=none; b=POihT62L3ckRNSkTgQ5bwClkZfWf9DVwTl3tA1AoUgv3y+LjSdZtLQeR2fSxYiie/TWQWjYphEGDmXvkURRfQq4Ayr1FrR1jIw1Tgch9BxZV5fOfsUTjpoeM1KKRbcz6A01FAY6eZvSUE5DO6eXUhZhigA69LgrzVzF9Vf0p9GQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722484384; c=relaxed/simple; bh=SZh3XCDSFmyPqUeH2ujcUUsjOZ0MyaFTjhvx5nanywQ=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=PW7OH/g3bV7d+QrmbI8mbwlJw/U2gCisRWDpd3Ax3r0b9kDSDbzm0HrN6Gnndxl7BUooY3Ggo2UjmxdwkUKfweRvEZpC1Fz5xOSwqi/x+O5MR+8f/ykHBBduZA+K1sAD/Ujwvv9mboAGjhK/Nzjy4LIxrejLBfJG4uilTgqdp64= 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=ivL4X512; arc=none smtp.client-ip=80.241.56.152 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="ivL4X512" Received: from smtp102.mailbox.org (smtp102.mailbox.org [10.196.197.102]) (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-102.mailbox.org (Postfix) with ESMTPS id 4WZFRX6l72z9skj; Thu, 1 Aug 2024 05:52:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1722484377; 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=o8hmGv4rMCoc1oB9Naj26I2ZF5t/5CBQ9CJf/mNy8IM=; b=ivL4X5127HkvMXRFkM+qZ53mAZaz5PnfrZCUQkyumyNPbBI6YC4cutP4Mi+YvtXtTUyw2O CC2CxZfWFc8uwfqxXU5UApky4pPMpxf/Q4wV7Ved4KbOyKnY+cvTjI0ueDGNOxpiAoDei/ jif0Mf3WWCI+0rBp4PGlpf5fjO5BiKSVxASgf8J++rx3bf5wBtmXwn3X/tZCEBnza6HWtq eKQX+DCyQz+coJ7cFEV03Is54gw6wn/ofRd8p11l39EMzpnaHFSFYvizVQV2cOTxlZQ++m qUV+rYx4VH2kVDHUart8WdjJckC+w5TruDVjAd5684fcTeMgiblNjEMzJgufeg== From: Aleksa Sarai Subject: [PATCH RFC v3 0/2] fhandle: expose u64 mount id to name_to_handle_at(2) Date: Thu, 01 Aug 2024 13:52:39 +1000 Message-Id: <20240801-exportfs-u64-mount-id-v3-0-be5d6283144a@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=H4sIAIcGq2YC/3XNsQ6CMBAG4Fcxna2hhVPqZGLiA7gaB1qu0gFKW mgghHe31kUHxv/uv+8W4tEZ9OS8W4jDYLyxXQz5fkdUU3UvpKaOmfCMFxkwoDj11g3a0/FY0Na O3RAbVKCUoKCUkCsSb3uH2kzJfZD77UqecdgYP1g3p1+BpdWX5dkGGxhlVAPoWnAGssSLmvumc gdl20QG/svkWwz/MEILEJqdULI/Zl3XN49rihAHAQAA 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: 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=2865; i=cyphar@cyphar.com; h=from:subject:message-id; bh=SZh3XCDSFmyPqUeH2ujcUUsjOZ0MyaFTjhvx5nanywQ=; b=owGbwMvMwCWmMf3Xpe0vXfIZT6slMaStZus5xb3xoeZKsfOVITXPWrMM+JXjJyuyzDlWryjZH crwdJZXRykLgxgXg6yYIss2P8/QTfMXX0n+tJINZg4rE8gQBi5OAZiIRQrDP/uzYVsuG+yckpBY LqA4J/Yg20n7mq7syXqvCze1hr5Ve8HI8O9DvOjdHy9Xf5F6orL02/yNiTq37jimxqptmv3HYYn WCg4A 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 Reviewed-by: Josef Bacik --- 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: c7b9563b58a77423d4c6e026ff831a69612b02fc change-id: 20240515-exportfs-u64-mount-id-9ebb5c58b53c Best regards,