On Sat, Sep 14, 2013 at 11:49:51AM +0900, Tetsuo Handa wrote: > Even bad code which has never tested failure case, the authors should already > know that "seq_printf() returns 0 on success case".
It is designed so that not testing failure case is normal approach for the majority of users. > - pos += seq_printf(s, "\tChannel number: %d\n", num_dma_channels); > + seq_puts(s, "DMA engine status\n"); > + seq_printf(s, "\tChannel number: %d\n", num_dma_channels); > > - return pos; > + return seq_overflow(s) : -1 : 0; > > for keeping the functionality. ITYM "for keeping the bug". Read seq_read(), please. Any negative value returned by ->show() is a hard error. It won't be retried with bigger buffer; read(2) will *fail*. With -EINVAL, in your case. We really, really should not return non-zero on overflow. Moreover, returning a _positive_ value (SEQ_SKIP, normally, but any positive will do the same thing) means "silently discard everything ->show() might have produced" Again, the normal return value of ->show() is 0 and that includes the case of overflow. THE ONLY reason to check for overflow early is when subsequent output of ->show() takes long to generate and we want to skip that and have seq_read() do realloc-and-call-show-again immediately. And in that case the right fix is often to get saner iterator and stop shoving everything into a single ->show() call... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
