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SubjectRe: [PATCH] jffs2: Don't add summary entry when MTD write fails
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Hello David:

> > + int ret;
> > +
> > + ret = mtd_writev(c->mtd, vecs, count, to, retlen);
> > +
> > if (!jffs2_is_writebuffered(c)) {
> > if (jffs2_sum_active()) {
> > int res;
> > +
> > + if (ret ||
> > + *retlen != iov_length((struct iovec *)
> vecs, count))
> > + return ret;
> > +
> > res = jffs2_sum_add_kvec(c, vecs, count,
> (uint32_t) to);
> > if (res) {
> > return res;
>
> OK... but perhaps we can dispense with the separate 'ret' and 'res'
> variables and the rats nest of conditions, and do something like:
>
> int ret;
>
> ret = mtd_writev(…);
>
> if (!ret && *retlen == iov_length(…) &&
> !jffs2_is_writebuffered(c) && jffs2_sum_active())
> ret = jffs2_sum_add_kvec(…);
>
> return ret;

While the logic is the same, will the compiler generate the same code?
When CONFIG_JFFS2_SUMMARY is not set, "if (jffs2_sum_active())" means "if
(0)", and I would assume that the compiler removes the whole clause, "if"
and all. However, I am not sure what happens with "if (!ret && whatever &&
0)".

That's why I was taking pains to keep the original control flow intact,
even if it's a rat's nest (it is). If I remember correctly,
jffs2_flash_direct_writev() is called quite often, and I didn't want
performance to suffer. I may be completely wrong here, of course, but then
why wasn't the original source code "if (!jffs2_is_writebuffered(c) &&
jffs2_sum_active())"?

Best regards,
Thomas

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