[v3] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)

Message ID	20240625151807.620812-1-mjguzik@gmail.com (mailing list archive)
State	New
Headers	show Received: from mail-ed1-f43.google.com (mail-ed1-f43.google.com [209.85.208.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C9A5176AA2; Tue, 25 Jun 2024 15:18:19 +0000 (UTC) From: Mateusz Guzik <mjguzik@gmail.com> To: brauner@kernel.org Cc: viro@zeniv.linux.org.uk, jack@suse.cz, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, axboe@kernel.dk, torvalds@linux-foundation.org, xry111@xry111.site, loongarch@lists.linux.dev, Mateusz Guzik <mjguzik@gmail.com> Subject: [PATCH v3] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...) Date: Tue, 25 Jun 2024 17:18:06 +0200 Message-ID: <20240625151807.620812-1-mjguzik@gmail.com> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit
Series	[v3] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...) \| expand [v3] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)

diff --git a/fs/internal.h b/fs/internal.h index 84f371193f74..1d820018e6dc 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: diff --git a/fs/stat.c b/fs/stat.c index 5039c34a385d..3778e605eac8 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->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; +} + +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; } @@ -683,16 +697,40 @@ 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, @@ -700,8 +738,23 @@ 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)); ret = do_statx(dfd, name, flags, mask, buffer); putname(name); diff --git a/io_uring/statx.c b/io_uring/statx.c index f7f9b202eec0..2b27af51fc12 100644 --- a/io_uring/statx.c +++ b/io_uring/statx.c @@ -23,6 +23,7 @@ struct io_statx { int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) { struct io_statx *sx = io_kiocb_to_cmd(req, struct io_statx); + struct filename *filename; const char __user *path; if (sqe->buf_index || sqe->splice_fd_in) @@ -36,14 +37,16 @@ int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) sx->buffer = u64_to_user_ptr(READ_ONCE(sqe->addr2)); sx->flags = READ_ONCE(sqe->statx_flags); - sx->filename = getname_flags(path, - getname_statx_lookup_flags(sx->flags)); - - if (IS_ERR(sx->filename)) { - int ret = PTR_ERR(sx->filename); - + if ((sx->flags & (AT_EMPTY_PATH | AT_STATX_SYNC_TYPE)) == + (AT_EMPTY_PATH | AT_STATX_SYNC_TYPE) && + vfs_empty_path(sx->dfd, path)) { sx->filename = NULL; - return ret; + } else { + filename = getname_flags(path, + getname_statx_lookup_flags(sx->flags)); + if (IS_ERR(filename)) + return PTR_ERR(filename); + sx->filename = filename; } req->flags |= REQ_F_NEED_CLEANUP; @@ -58,7 +61,10 @@ int io_statx(struct io_kiocb *req, unsigned int issue_flags) WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); - ret = do_statx(sx->dfd, sx->filename, sx->flags, sx->mask, sx->buffer); + if (sx->filename == NULL) + ret = do_statx_fd(sx->dfd, sx->flags, sx->mask, sx->buffer); + else + ret = do_statx(sx->dfd, sx->filename, sx->flags, sx->mask, sx->buffer); io_req_set_res(req, ret, 0); return IOU_OK; }

[v3] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)

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