block, bfq: return nbytes and not zero from struct cftype .write() method

commit fc8ebd01deeb12728c83381f6ec923e4a192ffd3 upstream.

The value that struct cftype .write() method returns is then directly
returned to userspace as the value returned by write() syscall, so it
should be the number of bytes actually written (or consumed) and not zero.

Returning zero from write() syscall makes programs like /bin/echo or bash
spin.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Fixes: e21b7a0b9887 ("block, bfq: add full hierarchical scheduling and cgroups support")
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 5d53e504acae58d02fa3d8c0b5cef4b625e758aa..4b571f3ea00966d026127fae931ad0398a81b82f 100644 (file)
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -887,7 +887,8 @@ static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
        if (ret)
                return ret;
 
-       return bfq_io_set_weight_legacy(of_css(of), NULL, weight);
+       ret = bfq_io_set_weight_legacy(of_css(of), NULL, weight);
+       return ret ?: nbytes;
 }
 
 static int bfqg_print_stat(struct seq_file *sf, void *v)