From patchwork Wed Sep 18 14:01:21 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miao Wang via B4 Relay X-Patchwork-Id: 13806912 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 70C2918C01A; Wed, 18 Sep 2024 14:01:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726668109; cv=none; b=r7bkamgowVshbckU4qBmmjjezjGr32bl24K8LdwiMm732vROmAwYoGVoJ6av2L6f17hIY4lOw6I7RoSjjo4S3WQQXgorLWFF1oVkRvuiYdF511UvP5DymS1kS4dfdPyHQvvsi9HB3Kl9Jl0bxzB3WIPupT+BM0rOWX0Az26xnGI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726668109; c=relaxed/simple; bh=SrjfI6AJkMF7a6Yl8Mz1p1+x5RAggVoecp0mMtBpEhc=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TyAaLgxzSochXk3NITAIq15XTFYMCXG8eOot4xV65Yeyx15GBOEmjnWDiu7zOsw9zvdQ0uuNCgeudbialVJ6tS+KPMd9mIrLlmu++ofrZKxhw3xX+UgVfhzjGXSBVvOgBhwHoi5voM/tk/yvV2JFdkS0Xw9W1pw467BHBTt/O3Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HBgm5reN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HBgm5reN" Received: by smtp.kernel.org (Postfix) with ESMTPS id 4D5CEC4CECE; Wed, 18 Sep 2024 14:01:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1726668109; bh=SrjfI6AJkMF7a6Yl8Mz1p1+x5RAggVoecp0mMtBpEhc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=HBgm5reNAr+rZxQOxQgZlwIG7owMM6OIIndSPYrnOYTFZTjsn/Xl1mT3KwQ82a1oD iCtitZNTEGR289ZXEki5QerBnBXtHCyHzraG0vGyOKGcoEuddzJ7EIA6UokyTDn0S1 3OqQo/xamrKYqfgf9jMp952jfdUruZ37e5ng+pBUko+iVaiycBgNS9p1GI6+gimMIb QLlndbGT8Z9ZET+QVZbhEfcZvQ12dyGhpypKZOfrEY7mPMuSJ+g/YneIUvq2qO0+I2 mOSoGyd9DJALZNLnbULB6Xf9qwL8GhnYy4V/yh/Qk5d3iehIgx4meE5MwYvd5O9Wfy BQvtxxy6LYF8w== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F084CCD1A5; Wed, 18 Sep 2024 14:01:49 +0000 (UTC) From: Miao Wang via B4 Relay Date: Wed, 18 Sep 2024 22:01:21 +0800 Subject: [PATCH v6.10 3/3] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240918-statx-stable-linux-6-10-y-v1-3-8364a071074f@gmail.com> References: <20240918-statx-stable-linux-6-10-y-v1-0-8364a071074f@gmail.com> In-Reply-To: <20240918-statx-stable-linux-6-10-y-v1-0-8364a071074f@gmail.com> To: Greg Kroah-Hartman , stable@vger.kernel.org Cc: Xi Ruoyao , Mateusz Guzik , Christian Brauner , Alexander Viro , Jan Kara , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , linux-fsdevel@vger.kernel.org, stable@vger.kernel.org, Miao Wang X-Mailer: b4 0.14.1 X-Developer-Signature: v=1; a=openpgp-sha256; l=8249; i=shankerwangmiao@gmail.com; h=from:subject:message-id; bh=9J/bYSPlXIhi6E9ZB6fXyrlVsF3FwIjzHhYa5Djr6II=; b=owEBbQKS/ZANAwAKAbAx48p7/tluAcsmYgBm6t1KfUnRmp/RO24B5ffmTM9lmVdAkJCLpExWt CDy7GA9pmSJAjMEAAEKAB0WIQREqPWPgPJBxluezBOwMePKe/7ZbgUCZurdSgAKCRCwMePKe/7Z budqEACnpGoT7Y0FlY2Hs2G5q/h3SoXGRAespgXTTIeFpKmWPIKeNlPnWKtyyLBIQTJMIzuABmQ VzY5fSizUDOH9hKyt6w2la06glIjq+0UXn8xpQUZwCY0zUfn/vHVNdzBjOx3KtHitTdyLERDw9x rLEOxCLye+X7wq+570ufY/bTjkPfWrWiTZjxHWkmYdgwo/MbGPj1CEJ/KS/vRFhVrTC3xxaRhkJ hpYc2qhM3KxOkpADfedtQijQYxjWDIfrqmx457NgeQrMdcNIk/Z2yUzkLs/MUqZ0+AVpeuaWkxK 9CkMzKARdApRrZ2Eoy/J5y4Xw/L+3Glrd3jkDnQWQeMmxnU7izK0tQIaxf6LvABRKeUnsWcDU1c IEBTTuB7dtDCyrAfY9QoKR7Q8CD5yM3QkHoULr0zOu8i0f4zNduz/y5/OB4LyieLTqj2JPs0dGe yuzRacpyxh0AugoGlfqW6awB+WxfZaJO6JF+hVpIl3npdRa3nttd4utogGk1j9WsQSAptX25o4k dT56Ivbok6mxkw+XEQk3Pz/NActtImZppXw64YHomixrU92Evjh2u6loAHgDa/tpeNMcvZ6qwue Fx2F/nGdWmho/X5BqYo1E3EeaBl8SqDlOYpKbiQmo4AAMhbzmY1a3yFtpQd3BJQfNVOpXMaNSr9 glbBWJcrl9U+YWg== X-Developer-Key: i=shankerwangmiao@gmail.com; a=openpgp; fpr=6FAEFF06B7D212A774C60BFDFA0D166D6632EF4A X-Endpoint-Received: by B4 Relay for shankerwangmiao@gmail.com/default with auth_id=189 X-Original-From: Miao Wang Reply-To: shankerwangmiao@gmail.com From: Mateusz Guzik commit 0ef625b upstream. The newly used helper also checks for empty ("") paths. NULL paths with any flag value other than AT_EMPTY_PATH go the usual route and end up with -EFAULT to retain compatibility (Rust is abusing calls of the sort to detect availability of statx). This avoids path lookup code, lockref management, memory allocation and in case of NULL path userspace memory access (which can be quite expensive with SMAP on x86_64). Benchmarked with statx(..., AT_EMPTY_PATH, ...) running on Sapphire Rapids, with the "" path for the first two cases and NULL for the last one. Results in ops/s: stock: 4231237 pre-check: 5944063 (+40%) NULL path: 6601619 (+11%/+56%) Signed-off-by: Mateusz Guzik Link: https://lore.kernel.org/r/20240625151807.620812-1-mjguzik@gmail.com Tested-by: Xi Ruoyao [brauner: use path_mounted() and other tweaks] Signed-off-by: Christian Brauner Cc: # 6.10.x Signed-off-by: Miao Wang Tested-by: Xi Ruoyao --- fs/internal.h | 14 ++++++++ fs/namespace.c | 13 ------- fs/stat.c | 111 ++++++++++++++++++++++++++++++++++++++++++--------------- 3 files changed, 97 insertions(+), 41 deletions(-) diff --git a/fs/internal.h b/fs/internal.h index ab2225136f60..f26454c60a98 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -247,6 +247,8 @@ extern const struct dentry_operations ns_dentry_operations; int getname_statx_lookup_flags(int flags); int do_statx(int dfd, struct filename *filename, unsigned int flags, unsigned int mask, struct statx __user *buffer); +int do_statx_fd(int fd, unsigned int flags, unsigned int mask, + struct statx __user *buffer); /* * fs/splice.c: @@ -321,3 +323,15 @@ struct stashed_operations { int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data, struct path *path); void stashed_dentry_prune(struct dentry *dentry); +/** + * path_mounted - check whether path is mounted + * @path: path to check + * + * Determine whether @path refers to the root of a mount. + * + * Return: true if @path is the root of a mount, false if not. + */ +static inline bool path_mounted(const struct path *path) +{ + return path->mnt->mnt_root == path->dentry; +} diff --git a/fs/namespace.c b/fs/namespace.c index e1ced589d835..0134eda41b71 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1846,19 +1846,6 @@ bool may_mount(void) return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); } -/** - * path_mounted - check whether path is mounted - * @path: path to check - * - * Determine whether @path refers to the root of a mount. - * - * Return: true if @path is the root of a mount, false if not. - */ -static inline bool path_mounted(const struct path *path) -{ - return path->mnt->mnt_root == path->dentry; -} - static void warn_mandlock(void) { pr_warn_once("=======================================================\n" diff --git a/fs/stat.c b/fs/stat.c index 0e8558f9c0b3..52fde6fe0086 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -214,6 +214,43 @@ int getname_statx_lookup_flags(int flags) return lookup_flags; } +static int vfs_statx_path(struct path *path, int flags, struct kstat *stat, + u32 request_mask) +{ + int error = vfs_getattr(path, stat, request_mask, flags); + + if (request_mask & STATX_MNT_ID_UNIQUE) { + stat->mnt_id = real_mount(path->mnt)->mnt_id_unique; + stat->result_mask |= STATX_MNT_ID_UNIQUE; + } else { + stat->mnt_id = real_mount(path->mnt)->mnt_id; + stat->result_mask |= STATX_MNT_ID; + } + + if (path_mounted(path)) + stat->attributes |= STATX_ATTR_MOUNT_ROOT; + stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT; + + /* Handle STATX_DIOALIGN for block devices. */ + if (request_mask & STATX_DIOALIGN) { + struct inode *inode = d_backing_inode(path->dentry); + + if (S_ISBLK(inode->i_mode)) + bdev_statx_dioalign(inode, stat); + } + + return error; +} + +static int vfs_statx_fd(int fd, int flags, struct kstat *stat, + u32 request_mask) +{ + CLASS(fd_raw, f)(fd); + if (!f.file) + return -EBADF; + return vfs_statx_path(&f.file->f_path, flags, stat, request_mask); +} + /** * vfs_statx - Get basic and extra attributes by filename * @dfd: A file descriptor representing the base dir for a relative filename @@ -243,36 +280,13 @@ static int vfs_statx(int dfd, struct filename *filename, int flags, retry: error = filename_lookup(dfd, filename, lookup_flags, &path, NULL); if (error) - goto out; - - error = vfs_getattr(&path, stat, request_mask, flags); - - if (request_mask & STATX_MNT_ID_UNIQUE) { - stat->mnt_id = real_mount(path.mnt)->mnt_id_unique; - stat->result_mask |= STATX_MNT_ID_UNIQUE; - } else { - stat->mnt_id = real_mount(path.mnt)->mnt_id; - stat->result_mask |= STATX_MNT_ID; - } - - if (path.mnt->mnt_root == path.dentry) - stat->attributes |= STATX_ATTR_MOUNT_ROOT; - stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT; - - /* Handle STATX_DIOALIGN for block devices. */ - if (request_mask & STATX_DIOALIGN) { - struct inode *inode = d_backing_inode(path.dentry); - - if (S_ISBLK(inode->i_mode)) - bdev_statx_dioalign(inode, stat); - } - + return error; + error = vfs_statx_path(&path, flags, stat, request_mask); path_put(&path); if (retry_estale(error, lookup_flags)) { lookup_flags |= LOOKUP_REVAL; goto retry; } -out: return error; } @@ -666,7 +680,8 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags, if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE) return -EINVAL; - /* STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests + /* + * STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests * from userland. */ mask &= ~STATX_CHANGE_COOKIE; @@ -678,16 +693,41 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags, return cp_statx(&stat, buffer); } +int do_statx_fd(int fd, unsigned int flags, unsigned int mask, + struct statx __user *buffer) +{ + struct kstat stat; + int error; + + if (mask & STATX__RESERVED) + return -EINVAL; + if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE) + return -EINVAL; + + /* + * STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests + * from userland. + */ + mask &= ~STATX_CHANGE_COOKIE; + + error = vfs_statx_fd(fd, flags, &stat, mask); + if (error) + return error; + + return cp_statx(&stat, buffer); +} + /** * sys_statx - System call to get enhanced stats * @dfd: Base directory to pathwalk from *or* fd to stat. - * @filename: File to stat or "" with AT_EMPTY_PATH + * @filename: File to stat or either NULL or "" with AT_EMPTY_PATH * @flags: AT_* flags to control pathwalk. * @mask: Parts of statx struct actually required. * @buffer: Result buffer. * * Note that fstat() can be emulated by setting dfd to the fd of interest, - * supplying "" as the filename and setting AT_EMPTY_PATH in the flags. + * supplying "" (or preferably NULL) as the filename and setting AT_EMPTY_PATH + * in the flags. */ SYSCALL_DEFINE5(statx, int, dfd, const char __user *, filename, unsigned, flags, @@ -695,8 +735,23 @@ SYSCALL_DEFINE5(statx, struct statx __user *, buffer) { int ret; + unsigned lflags; struct filename *name; + /* + * Short-circuit handling of NULL and "" paths. + * + * For a NULL path we require and accept only the AT_EMPTY_PATH flag + * (possibly |'d with AT_STATX flags). + * + * However, glibc on 32-bit architectures implements fstatat as statx + * with the "" pathname and AT_NO_AUTOMOUNT | AT_EMPTY_PATH flags. + * Supporting this results in the uglification below. + */ + lflags = flags & ~(AT_NO_AUTOMOUNT | AT_STATX_SYNC_TYPE); + if (lflags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename)) + return do_statx_fd(dfd, flags & ~AT_NO_AUTOMOUNT, mask, buffer); + name = getname_flags(filename, getname_statx_lookup_flags(flags), NULL); ret = do_statx(dfd, name, flags, mask, buffer); putname(name);