On Mon, Jan 18, 2021 at 07:31:13PM +0100, Christoph Hellwig wrote: > On Mon, Jan 18, 2021 at 06:17:12PM +0000, Matthew Wilcox wrote: > > On Mon, Jan 18, 2021 at 07:13:38PM +0100, Christoph Hellwig wrote: > > > On Thu, Jan 14, 2021 at 07:47:06PM +0000, Matthew Wilcox (Oracle) wrote: > > > > It's often inconvenient to use BIO_MAX_PAGES due to min() requiring the > > > > sign to be the same. Introduce bio_limit() and change BIO_MAX_PAGES to > > > > be unsigned to make it easier for the users. > > > > > > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > > > > > > I like the helper, but I'm not too happy with the naming. Why not > > > something like bio_guess_nr_segs() or similar? > > > > This feels like it's a comment on an entirely different patch, like this one: > > > > https://git.infradead.org/users/willy/pagecache.git/commitdiff/fe9841debe24e15100359acadd0b561bbb2dceb1 > > > > bio_limit() doesn't guess anything, it just clamps the argument to > > BIO_MAX_PAGES (which is itself misnamed; it's BIO_MAX_SEGS now) > > No, it was for thi patch. Yes, it divides and clamps. Which is sort of > a guess as often we might need less of them. That being said I'm not > very fond of my suggestion either, but limit sounds wrong as well. bio_limit() doesn't divide. Some of the callers divide. +static inline unsigned int bio_limit(unsigned int nr_segs) +{ + return min(nr_segs, BIO_MAX_PAGES); +} I'd rather the callers didn't have to worry about this at all (just pass in a number and then deal with however many bvecs you were given), but there are callers which depend on the current if-too-big-return-NULL behaviour, and I don't want to track all of those down and fix them. I chose limit because it's imposing the bio's limit. Could be called bio_clamp(), but the bio also doesn't impose a minimum, so that seemed wrong.
