[PATCH RFC 6/8] fs: sandboxfs: add sandbox_fs_get_blocksize()

[Simon Glass]

On Tue, 28 Jun 2022 at 01:28, Qu Wenruo <wqu at suse.com> wrote:
>
> This is to make sandboxfs to report blocksize it supports for
> _fs_read() to handle unaligned read.
>
> Unlike all other fses, sandboxfs can handle unaligned read/write without
> any problem since it's calling read()/write(), which doesn't bother the
> blocksize at all.
>
> This change is mostly to make testing of _fs_read() much easier.
>
> Cc: Simon Glass <sjg at chromium.org>
> Signed-off-by: Qu Wenruo <wqu at suse.com>
> ---
>  arch/sandbox/cpu/os.c  | 11 +++++++++++
>  fs/fs.c                |  2 +-
>  fs/sandbox/sandboxfs.c | 14 ++++++++++++++
>  include/os.h           |  8 ++++++++
>  include/sandboxfs.h    |  1 +
>  5 files changed, 35 insertions(+), 1 deletion(-)

Reviewed-by: Simon Glass <sjg at chromium.org>

with a comment as requested below

>
> diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
> index 5ea54179176c..6c29f29bdd9b 100644
> --- a/arch/sandbox/cpu/os.c
> +++ b/arch/sandbox/cpu/os.c
> @@ -46,6 +46,17 @@ ssize_t os_read(int fd, void *buf, size_t count)
>         return read(fd, buf, count);
>  }
>
> +ssize_t os_get_blocksize(int fd)
> +{
> +       struct stat stat = {0};
> +       int ret;
> +
> +       ret = fstat(fd, &stat);
> +       if (ret < 0)
> +               return -errno;
> +       return stat.st_blksize;
> +}
> +
>  ssize_t os_write(int fd, const void *buf, size_t count)
>  {
>         return write(fd, buf, count);
> diff --git a/fs/fs.c b/fs/fs.c
> index 7e4ead9b790b..337d5711c28c 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -261,7 +261,7 @@ static struct fstype_info fstypes[] = {
>                 .exists = sandbox_fs_exists,
>                 .size = sandbox_fs_size,
>                 .read = fs_read_sandbox,
> -               .get_blocksize = fs_get_blocksize_unsupported,
> +               .get_blocksize = sandbox_fs_get_blocksize,
>                 .write = fs_write_sandbox,
>                 .uuid = fs_uuid_unsupported,
>                 .opendir = fs_opendir_unsupported,
> diff --git a/fs/sandbox/sandboxfs.c b/fs/sandbox/sandboxfs.c
> index 4ae41d5b4db1..130fee088621 100644
> --- a/fs/sandbox/sandboxfs.c
> +++ b/fs/sandbox/sandboxfs.c
> @@ -55,6 +55,20 @@ int sandbox_fs_read_at(const char *filename, loff_t pos, void *buffer,
>         return ret;
>  }
>
> +int sandbox_fs_get_blocksize(const char *filename)
> +{
> +       int fd;
> +       int ret;
> +
> +       fd = os_open(filename, OS_O_RDONLY);
> +       if (fd < 0)
> +               return fd;
> +
> +       ret = os_get_blocksize(fd);
> +       os_close(fd);
> +       return ret;
> +}
> +
>  int sandbox_fs_write_at(const char *filename, loff_t pos, void *buffer,
>                         loff_t towrite, loff_t *actwrite)
>  {
> diff --git a/include/os.h b/include/os.h
> index 10e198cf503e..a864d9ca39b2 100644
> --- a/include/os.h
> +++ b/include/os.h
> @@ -26,6 +26,14 @@ struct sandbox_state;
>   */
>  ssize_t os_read(int fd, void *buf, size_t count);
>
> +/**
> + * Get the optimial blocksize through stat() call.
> + *
> + * @fd:                File descriptor as returned by os_open()
> + * Return:     >=0 for the blocksize. <0 for error.
> + */
> +ssize_t os_get_blocksize(int fd);
> +
>  /**
>   * Access to the OS write() system call
>   *
> diff --git a/include/sandboxfs.h b/include/sandboxfs.h
> index 783dd5c88a73..6937068f7b82 100644
> --- a/include/sandboxfs.h
> +++ b/include/sandboxfs.h
> @@ -32,6 +32,7 @@ void sandbox_fs_close(void);
>  int sandbox_fs_ls(const char *dirname);
>  int sandbox_fs_exists(const char *filename);
>  int sandbox_fs_size(const char *filename, loff_t *size);
> +int sandbox_fs_get_blocksize(const char *filename);

Please add a full comment.

>  int fs_read_sandbox(const char *filename, void *buf, loff_t offset, loff_t len,
>                     loff_t *actread);
>  int fs_write_sandbox(const char *filename, void *buf, loff_t offset,
> --
> 2.36.1
>

Regards,
Simon