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(cst-prg-81-171.cust.vodafone.cz. [46.135.81.171]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a724162f037sm337272566b.194.2024.06.25.04.00.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Jun 2024 04:00:56 -0700 (PDT) From: Mateusz Guzik 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 Subject: [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...) Date: Tue, 25 Jun 2024 13:00:28 +0200 Message-ID: <20240625110029.606032-3-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240625110029.606032-1-mjguzik@gmail.com> References: <20240625110029.606032-1-mjguzik@gmail.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The newly used helper also checks for 0-sized buffers. 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). statx with AT_EMPTY_PATH paired with "" or NULL argument as appropriate issued on Sapphire Rapids (ops/s): stock: 4231237 0-check: 5944063 (+40%) NULL path: 6601619 (+11%/+56%) Signed-off-by: Mateusz Guzik --- fs/internal.h | 2 ++ fs/stat.c | 90 ++++++++++++++++++++++++++++++++++-------------- io_uring/statx.c | 23 +++++++------ 3 files changed, 80 insertions(+), 35 deletions(-) diff --git a/fs/internal.h b/fs/internal.h index 1caa6a8f666f..0a018ebcaf49 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -244,6 +244,8 @@ 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 106684034fdb..1214826f3a36 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; } @@ -677,6 +691,29 @@ 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. @@ -696,6 +733,9 @@ SYSCALL_DEFINE5(statx, int ret; struct filename *name; + if (flags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename)) + return do_statx_fd(dfd, flags, mask, buffer); + name = getname_flags(filename, getname_statx_lookup_flags(flags), NULL); ret = do_statx(dfd, name, flags, mask, buffer); putname(name); diff --git a/io_uring/statx.c b/io_uring/statx.c index abb874209caa..fe967ecb1762 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) @@ -36,15 +37,14 @@ 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), - NULL); - - if (IS_ERR(sx->filename)) { - int ret = PTR_ERR(sx->filename); - - sx->filename = NULL; - return ret; + sx->filename = NULL; + if (!(sx->flags == AT_EMPTY_PATH && vfs_empty_path(sx->dfd, path))) { + filename = getname_flags(path, + getname_statx_lookup_flags(sx->flags), + NULL); + if (IS_ERR(filename)) + return PTR_ERR(filename); + sx->filename = filename; } req->flags |= REQ_F_NEED_CLEANUP; @@ -59,7 +59,10 @@ 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; } -- 2.43.0