Re: [PATCH v3 1/2] file-posix: probe discard alignment on Linux block devices

[Eric Blake]

On Mon, Apr 14, 2025 at 04:12:13PM -0400, Stefan Hajnoczi wrote:
> Populate the pdiscard_alignment block limit so the block layer is able
> align discard requests correctly.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  block/file-posix.c | 67 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 66 insertions(+), 1 deletion(-)
> 

> +static int get_sysfs_u32_val(struct stat *st, const char *attribute,
> +                             uint32_t *u32)
> +{
> +    g_autofree char *str = NULL;
> +    const char *end;
> +    unsigned int val;
> +    int ret;
> +
> +    ret = get_sysfs_str_val(st, attribute, &str);
> +    if (ret < 0) {
> +        return ret;
> +    }
> +
> +    /* The file is ended with '\n', pass 'end' to accept that. */
> +    ret = qemu_strtoui(str, &end, 10, &val);
> +    if (ret == 0 && end && *end == '\0') {

This doesn't match the comment.  If we expect the file contents to end
in \n, then this should be checking *end == '\n', not '\0'.

> +        *u32 = val;
> +    }
> +    return ret;
> +}
>  #endif
>  

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org