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Date: Tue, 25 Jun 2024 22:09:10 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: brauner@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
io-uring@...r.kernel.org, axboe@...nel.dk, torvalds@...ux-foundation.org,
xry111@...111.site, loongarch@...ts.linux.dev
Subject: Re: [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)
On Tue, Jun 25, 2024 at 7:01 PM Mateusz Guzik <mjguzik@...il.com> wrote:
>
> 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 <mjguzik@...il.com>
Hi, Ruoyao,
I'm a bit confused. Ii this patch a replacement of your recent patch?
Huacai
> ---
> 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
>
>
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