* [PATCH] staging: lustre: Fix unneeded byte-ordering cast @ 2018-03-17 9:15 Justin Skists 2018-03-20 1:06 ` NeilBrown 0 siblings, 1 reply; 3+ messages in thread From: Justin Skists @ 2018-03-17 9:15 UTC (permalink / raw) To: devel; +Cc: Greg Kroah-Hartman, Patrick Farrell, NeilBrown, linux-kernel Fix sparse warning: CHECK drivers/staging//lustre/lnet/lnet/acceptor.c drivers/staging//lustre/lnet/lnet/acceptor.c:243:30: warning: cast to restricted __le32 LNET_PROTO_TCP_MAGIC, as a define, is already CPU byte-ordered when compared to 'magic', so no need for a cast. Signed-off-by: Justin Skists <j.skists@gmail.com> --- drivers/staging/lustre/lnet/lnet/acceptor.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/lustre/lnet/lnet/acceptor.c b/drivers/staging/lustre/lnet/lnet/acceptor.c index fb478e20e204..13e981781b9a 100644 --- a/drivers/staging/lustre/lnet/lnet/acceptor.c +++ b/drivers/staging/lustre/lnet/lnet/acceptor.c @@ -240,7 +240,7 @@ lnet_accept(struct socket *sock, __u32 magic) return -EPROTO; } - if (magic == le32_to_cpu(LNET_PROTO_TCP_MAGIC)) + if (magic == LNET_PROTO_TCP_MAGIC) str = "'old' socknal/tcpnal"; else str = "unrecognised"; -- 2.16.2 _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] staging: lustre: Fix unneeded byte-ordering cast 2018-03-17 9:15 [PATCH] staging: lustre: Fix unneeded byte-ordering cast Justin Skists @ 2018-03-20 1:06 ` NeilBrown 2018-03-20 15:50 ` Justin Skists 0 siblings, 1 reply; 3+ messages in thread From: NeilBrown @ 2018-03-20 1:06 UTC (permalink / raw) To: Justin Skists, devel; +Cc: Greg Kroah-Hartman, Patrick Farrell, linux-kernel [-- Attachment #1.1: Type: text/plain, Size: 2203 bytes --] On Sat, Mar 17 2018, Justin Skists wrote: > Fix sparse warning: > > CHECK drivers/staging//lustre/lnet/lnet/acceptor.c > drivers/staging//lustre/lnet/lnet/acceptor.c:243:30: warning: cast to > restricted __le32 > > LNET_PROTO_TCP_MAGIC, as a define, is already CPU byte-ordered when > compared to 'magic', so no need for a cast. > > Signed-off-by: Justin Skists <j.skists@gmail.com> > --- > drivers/staging/lustre/lnet/lnet/acceptor.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/staging/lustre/lnet/lnet/acceptor.c b/drivers/staging/lustre/lnet/lnet/acceptor.c > index fb478e20e204..13e981781b9a 100644 > --- a/drivers/staging/lustre/lnet/lnet/acceptor.c > +++ b/drivers/staging/lustre/lnet/lnet/acceptor.c > @@ -240,7 +240,7 @@ lnet_accept(struct socket *sock, __u32 magic) > return -EPROTO; > } > > - if (magic == le32_to_cpu(LNET_PROTO_TCP_MAGIC)) > + if (magic == LNET_PROTO_TCP_MAGIC) > str = "'old' socknal/tcpnal"; > else > str = "unrecognised"; This code is almost completely irrelevant (it just choose which error message to use when failing), but we may as well get it right and I cannot see why your change is a fix. "magic" was passed as an argument from lnet_acceptor() to lnet_accept(), and lnet_acceptor() got it by reading bytes off the network with lnet_sock_read(). My knowledge is far from complete, but from what I've seen, lustre sends data in host-byte-order on the sender, and expects the receiver to determine which byte-order that is (often by looking at a "magic" word like this) and do any byte-swap that is necessary. While I agree that LNET_PROTO_TCP_MAGIC is in host-byte-order so calling le32_to_cpu() on it makes no sense, I don't agree that "magic" is also host byte-ordered. I suspect a more correct fix would be to use lnet_accept_magic(magic, LNET_PROTO_TCP_MAGIC) as the condition of the if(). This is consistent with other code that tests magic, and it is consistent with the general understanding that "magic" should be in host-byte-order for the peer which sent the message. Could you resubmit with that change? Thanks, NeilBrown [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 832 bytes --] [-- Attachment #2: Type: text/plain, Size: 169 bytes --] _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] staging: lustre: Fix unneeded byte-ordering cast 2018-03-20 1:06 ` NeilBrown @ 2018-03-20 15:50 ` Justin Skists 0 siblings, 0 replies; 3+ messages in thread From: Justin Skists @ 2018-03-20 15:50 UTC (permalink / raw) To: NeilBrown; +Cc: devel, Greg Kroah-Hartman, Patrick Farrell, linux-kernel On 20 March 2018 at 01:06, NeilBrown <neilb@suse.com> wrote: > On Sat, Mar 17 2018, Justin Skists wrote: > >> Fix sparse warning: >> >> CHECK drivers/staging//lustre/lnet/lnet/acceptor.c >> drivers/staging//lustre/lnet/lnet/acceptor.c:243:30: warning: cast to >> restricted __le32 >> >> LNET_PROTO_TCP_MAGIC, as a define, is already CPU byte-ordered when >> compared to 'magic', so no need for a cast. >> >> Signed-off-by: Justin Skists <j.skists@gmail.com> >> --- >> drivers/staging/lustre/lnet/lnet/acceptor.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/staging/lustre/lnet/lnet/acceptor.c b/drivers/staging/lustre/lnet/lnet/acceptor.c >> index fb478e20e204..13e981781b9a 100644 >> --- a/drivers/staging/lustre/lnet/lnet/acceptor.c >> +++ b/drivers/staging/lustre/lnet/lnet/acceptor.c >> @@ -240,7 +240,7 @@ lnet_accept(struct socket *sock, __u32 magic) >> return -EPROTO; >> } >> >> - if (magic == le32_to_cpu(LNET_PROTO_TCP_MAGIC)) >> + if (magic == LNET_PROTO_TCP_MAGIC) >> str = "'old' socknal/tcpnal"; >> else >> str = "unrecognised"; > > This code is almost completely irrelevant (it just choose which error > message to use when failing), but we may as well get it right and I > cannot see why your change is a fix. I admit that the change is trivial, and, in hindsight, the word fix is a little "strong". The rationale was that the if-statement, as it was, probably wouldn't work as intented on big-endian systems. I chose this sparse warning to test the waters, as it was an isolated change, before I thought about proposing a bigger change: There are quite a few sparse warning in regards to struct lnet_hdr with regards to __u32 vs. __le32 (etc.) restricted castings. > I suspect a more correct fix would be to use > lnet_accept_magic(magic, LNET_PROTO_TCP_MAGIC) > as the condition of the if(). This is consistent with other code that > tests magic, and it is consistent with the general understanding that > "magic" should be in host-byte-order for the peer which sent the > message. > > Could you resubmit with that change? I agree that your suggestion is a much better fix. As Greg has already accepted the patch in question into staging-next, would the correct course of action be for me to submit a new patch with a "fixes" tag based on staging-next? Or would Greg prefer to drop the previous one for a fresh v2? Regards, Justin. _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-03-20 15:50 UTC | newest] Thread overview: 3+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2018-03-17 9:15 [PATCH] staging: lustre: Fix unneeded byte-ordering cast Justin Skists 2018-03-20 1:06 ` NeilBrown 2018-03-20 15:50 ` Justin Skists
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