On Tue, Apr 24, 2018 at 10:52:41AM +0800, Su Yue wrote:
>
>
> On 01/24/2018 03:42 AM, David Sterba wrote:
> > On Sun, Jan 07, 2018 at 01:54:21PM -0800, Rosen Penev wrote:
> >> As btrfs is specific to Linux, %m can be used instead of strerror(errno)
> >> in format strings. This has some size reduction benefits for embedded
> >> systems.
> >
> > Makes sense.
> >
> >> glibc, musl, and uclibc-ng all support %m as a modifier to printf.
> >> A quick glance at the BIONIC libc source indicates that it has
> >> support for %m as well. BSDs and Windows do not but I do believe
> >> them to be beyond the scope of btrfs-progs.
> >
> > Thanks for checking the compatibility. The %m can be substituted
> > by a wrapper if this becomes a problem in the future.
> >
> It seems a little problem in output now since it's not caused by this
> patch.
>
> $ touch /tmp/tmp
> $ btrfs-image -r /tmp/tmp /tmp/test.img
> ERROR: unable to read cluster: Success
That's probably because there's also 0 in the condition (line 1967):
1966 ret = fread(cluster, BLOCK_SIZE, 1, mdres->in);
1967 if (ret <= 0) {
1968 error("unable to read cluster: %m");
1969 return -EIO;
1970 }
1971 ret = 0;
We'd need to distinguish the < 0 and == 0 cases, and in one we can use
the %m as the errno will be set.
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