Messages in this thread | | | Date | Thu, 11 Aug 2011 09:26:34 -0400 | From | Chris Metcalf <> | Subject | Re: [PATCH] nfs: fix a couple of minor portability issues |
| |
On 8/10/2011 6:02 PM, Boaz Harrosh wrote: > On 08/10/2011 10:56 AM, Chris Metcalf wrote: >> Building on tilepro revealed two minor portability issues: the >> blocklayout.c file used prefetchw() without #include <linux/prefetch.h>, >> and the nfs4filelayout.c file used do_div() on an s64 not a u64. >> This change fixes those two issues so the NFS code builds on tilepro. >> >> [...] >> diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c >> index e8915d4..6976a72 100644 >> --- a/fs/nfs/nfs4filelayout.c >> +++ b/fs/nfs/nfs4filelayout.c >> @@ -48,13 +48,13 @@ filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg, >> loff_t offset) >> { >> u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count; >> - u64 tmp; >> + u64 tmp, uoff; >> >> offset -= flseg->pattern_offset; >> - tmp = offset; >> + tmp = uoff = offset; >> do_div(tmp, stripe_width); >> >> - return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit); >> + return tmp * flseg->stripe_unit + do_div(uoff, flseg->stripe_unit); > For proper u64 divisions it is best to use the div_u64 (and div64_u64) and not > use do_div. (And please don't add an unnecessary variable, just use a cast)
You can't use a cast with do_div() or you get errors about non-lvalues.
And the context here is that we want the remainder, not the divided result, so we'd need a temporary variable anyway if we were going to use a routine from math64.h, presumably div_u64_rem(). But that's just an inline wrapper around do_div() anyway, so it's no more efficient, and not obviously any less "cluttered" in the source code here. The original code author (who I'm adding belatedly to this email) may have a stronger opinion.
I'm not the author or maintainer of this code, I just want it to compile without warning on 32-bit architectures :-)
-- Chris Metcalf, Tilera Corp. http://www.tilera.com
| |