Re: [PATCH v2 3/8] vfs: introduce generic_file_rw_checks()

Darrick J. Wong
2019-05-28T16:15:03Z

On Sun, May 26, 2019 at 09:10:54AM +0300, Amir Goldstein wrote:
> Factor out helper with some checks on in/out file that are
> common to clone_file_range and copy_file_range.
>
> Suggested-by: Darrick J. Wong <darrick.wong@oracle.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
> fs/read_write.c | 38 +++++++++++---------------------------
> include/linux/fs.h | 1 +
> mm/filemap.c | 24 ++++++++++++++++++++++++
> 3 files changed, 36 insertions(+), 27 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index b63dcb4e4fe9..f1900bdb3127 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1617,17 +1617,18 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out,
> size_t len, unsigned int flags)
> {
> - struct inode *inode_in = file_inode(file_in);
> - struct inode *inode_out = file_inode(file_out);
> ssize_t ret;
>
> if (flags != 0)
> return -EINVAL;
>
> - if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
> - return -EISDIR;
> - if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
> - return -EINVAL;
> + /* this could be relaxed once a method supports cross-fs copies */
> + if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
> + return -EXDEV;
> +
> + ret = generic_file_rw_checks(file_in, file_out);
> + if (unlikely(ret))
> + return ret;
>
> ret = rw_verify_area(READ, file_in, &pos_in, len);
> if (unlikely(ret))
> @@ -1637,15 +1638,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> if (unlikely(ret))
> return ret;
>
> - if (!(file_in->f_mode & FMODE_READ) ||
> - !(file_out->f_mode & FMODE_WRITE) ||
> - (file_out->f_flags & O_APPEND))
> - return -EBADF;
> -
> - /* this could be relaxed once a method supports cross-fs copies */
> - if (inode_in->i_sb != inode_out->i_sb)
> - return -EXDEV;
> -
> if (len == 0)
> return 0;
>
> @@ -2013,29 +2005,21 @@ loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out,
> loff_t len, unsigned int remap_flags)
> {
> - struct inode *inode_in = file_inode(file_in);
> - struct inode *inode_out = file_inode(file_out);
> loff_t ret;
>
> WARN_ON_ONCE(remap_flags & REMAP_FILE_DEDUP);
>
> - if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
> - return -EISDIR;
> - if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
> - return -EINVAL;
> -
> /*
> * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on
> * the same mount. Practically, they only need to be on the same file
> * system.
> */
> - if (inode_in->i_sb != inode_out->i_sb)
> + if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
> return -EXDEV;
>
> - if (!(file_in->f_mode & FMODE_READ) ||
> - !(file_out->f_mode & FMODE_WRITE) ||
> - (file_out->f_flags & O_APPEND))
> - return -EBADF;
> + ret = generic_file_rw_checks(file_in, file_out);
> + if (ret < 0)
> + return ret;
>
> if (!file_in->f_op->remap_file_range)
> return -EOPNOTSUPP;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index ea17858310ff..89b9b73eb581 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3049,6 +3049,7 @@ extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
> extern int generic_remap_checks(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out,
> loff_t *count, unsigned int remap_flags);
> +extern int generic_file_rw_checks(struct file *file_in, struct file *file_out);
> extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
> extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
> extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c5af80c43d36..798aac92cd76 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3040,6 +3040,30 @@ int generic_remap_checks(struct file *file_in, loff_t pos_in,
> return 0;
> }
>
> +
> +/*
> + * Performs common checks before doing a file copy/clone
> + * from @file_in to @file_out.
> + */
> +int generic_file_rw_checks(struct file *file_in, struct file *file_out)
> +{
> + struct inode *inode_in = file_inode(file_in);
> + struct inode *inode_out = file_inode(file_out);
> +
> + /* Don't copy dirs, pipes, sockets... */
> + if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
> + return -EISDIR;
> + if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
> + return -EINVAL;
> +
> + if (!(file_in->f_mode & FMODE_READ) ||
> + !(file_out->f_mode & FMODE_WRITE) ||
> + (file_out->f_flags & O_APPEND))
> + return -EBADF;
> +
> + return 0;
> +}

/me wishes all these generic vfs io check helpers weren't all being
stuffed into mm/ but that's a refactoring for a different patchset...

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> +
> int pagecache_write_begin(struct file *file, struct address_space *mapping,
> loff_t pos, unsigned len, unsigned flags,
> struct page **pagep, void **fsdata)
> --
> 2.17.1
>