On Thu, Dec 13, 2012 at 11:25:29AM +1100, NeilBrown wrote:
>
>
> commit 5604b35a61e22930873ffc4e9971002f578e7978
> nfs-utils: Increase the stdio file buffer size for procfs files
>
> changed writes to some sysfs files to be line buffered (_IOLBF) where
> they weren't before. While this probably makes sense, it introduced a bug.
>
> With fully buffered streams, you don't expect to get an error until you
> call fflush().
> With line buffered streams you can get the error from fprintf() et al.
>
> qword_eol() only tests the return from fflush(), not from fprintf(). Consequently
> errors were not noticed.
>
> One result of this is that if you export, with crossmnt, a filesystem underneath
> which are mounted non-exportable filesystems (e.g. /proc) then an 'ls -l' on the
> client will block indefinitely waiting for a meaningful 'yes' or 'no' from the
> server, but will never get one.
>
> This patch changes qword_eol to test both fprintf and fflush.
Makes sense to me.--b.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
>
> diff --git a/support/nfs/cacheio.c b/support/nfs/cacheio.c
> index e641c45..61e07a8 100644
> --- a/support/nfs/cacheio.c
> +++ b/support/nfs/cacheio.c
> @@ -162,11 +162,16 @@ int qword_eol(FILE *f)
> {
> int err;
>
> - fprintf(f,"\n");
> - err = fflush(f);
> - if (err) {
> - xlog_warn("qword_eol: fflush failed: errno %d (%s)",
> + err = fprintf(f,"\n");
> + if (err < 0) {
> + xlog_warn("qword_eol: fprintf failed: errno %d (%s)",
> errno, strerror(errno));
> + } else {
> + err = fflush(f);
> + if (err) {
> + xlog_warn("qword_eol: fflush failed: errno %d (%s)",
> + errno, strerror(errno));
> + }
> }
> /*
> * We must send one line (and one line only) in a single write
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