Messages in this thread | | | Date | Mon, 3 Feb 2014 14:47:20 +0100 | Subject | Re: [PATCH -next 2/2] bcache: Use max_t() when comparing different types | From | Geert Uytterhoeven <> |
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On Wed, Jan 15, 2014 at 12:06 PM, Joe Perches <joe@perches.com> wrote: > On Wed, 2014-01-15 at 10:06 +0100, Geert Uytterhoeven wrote: >> drivers/md/bcache/btree.c: In function ‘insert_u64s_remaining’: >> drivers/md/bcache/btree.c:1816: warning: comparison of distinct pointer types lacks a cast > [] >> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c > [] >> @@ -1813,7 +1813,7 @@ static size_t insert_u64s_remaining(struct btree *b) >> if (b->keys.ops->is_extents) >> ret -= KEY_MAX_U64S; >> >> - return max(ret, 0L); >> + return max_t(ssize_t, ret, 0L); > > why not > return max(ret, 0);
Indeed, that also works, on both 32-bit and 64-bit. Will resend, now all the issues moved from -next to Linus' tree.
> I think it odd that: > > drivers/md/bcache/bset.h:static inline size_t bch_btree_keys_u64s_remaining(struct btree_keys *b) > > and: > > static size_t insert_u64s_remaining(struct btree *b) > { > ssize_t ret = bch_btree_keys_u64s_remaining(&b->keys); > > /* > * Might land in the middle of an existing extent and have to split it > */ > if (b->keys.ops->is_extents) > ret -= KEY_MAX_U64S; > > return max(ret, 0L); > } > > so the only use of that size_t inline is cast to ssize_t
If the value returned by bch_btree_keys_u64s_remaining() is smaller than KEY_MAX_U64S, it must stay negative after the subtraction, instead of wrapping around to a big positive number. That's why ret is ssize_t and not size_t.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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