On Fri, Oct 13, 2023 at 06:28:33AM +0200, Christoph Hellwig wrote:
> On Thu, Oct 12, 2023 at 03:11:06PM -0700, Darrick J. Wong wrote:
> > Hmm, so you want to go from:
> >
> > union xfs_rtword_ondisk *start, *end, *b;
> >
> > start = b = xfs_rbmblock_wordptr(bp, startword);
> > end = xfs_rbmblock_wordptr(bp, endword);
> >
> > while (b < end) {
> > somevalue = xfs_rtbitmap_getword(mp, b);
> > somevalue |= somemask;
> > xfs_rtbitmap_setword(mp, b, somevalue);
> > b++;
> > }
> >
> > xfs_trans_log_buf(tp, bp, start - bp->b_addr, b - bp->b_addr);
> >
> > to something like:
> >
> > for (word = startword; word <= endword; word++) {
> > somevalue = xfs_rtbitmap_getword(mp, b);
> > somevalue |= somemask;
> > xfs_rtbitmap_setword(mp, bp, word, somevalue);
> > }
> > xfs_rtbitmap_log_buf(tp, bp, startword, endword);
>
> Yes. (although xfs_rtbitmap_log_buf can't just take the words directly
> of course, and the xfs_rtbitmap_getword needs word and not the now
> not existing b).
>
> > I think that could be done with relatively little churn, though it's
> > unfortunate that the second version does 2x(shift + addition) each time
> > it goes through the loop instead of the pointer increment that the first
> > version does.
>
> I don't really think it matter compared to all the other overhead,
> and it keeps a much nicer API.
<nod> I suppose one could go the horrid iter function route to get
around the multiply, though at this point there's an awful lot of code
to do something very simple:
struct xfs_rbmword_cur {
struct xfs_buf *bp;
xfs_rtword_t *wordptr;
unsigned int endword;
unsigned int word;
};
static inline bool
xfs_rtbitmap_word_iter(
struct xfs_rbmword_cur *cur,
xfs_rtword_t *val)
{
if (cur->word >= cur->endword)
return false;
if (!cur->wordptr)
cur->wordptr = xfs_rbmblock_wordptr(cur->bp, cur->word);
*val = *cur->wordptr;
cur->word++;
cur->wordptr++;
return true;
}
static inline void
xfs_rtbitmap_word_set(
struct xfs_rbmword_cur *cur,
xfs_rtword_t val)
{
*(cur->wordptr - 1) = val;
}
Usage:
struct xfs_rbword_cur cur = {
.bp = bp,
.word = startword,
.endword = endword,
};
xfs_rtword_t val;
while (xfs_rtbitmap_word_iter(&cur, &val)) {
val |= somemask;
xfs_rtbitmap_word_set(cur, val);
}
xfs_rtbitmap_log_buf(tp, bp, startword, endword);
--D
