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Message-ID: <1403398834.2177.41.camel@dabdike.int.hansenpartnership.com> Date: Sat, 21 Jun 2014 18:00:34 -0700 From: James Bottomley <James.Bottomley@...senPartnership.com> To: Al Viro <viro@...IV.linux.org.uk> Cc: Theodore Ts'o <tytso@....edu>, Dave Chinner <david@...morbit.com>, Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org Subject: Re: 32-bit bug in iovec iterator changes On Sun, 2014-06-22 at 01:53 +0100, Al Viro wrote: > On Sat, Jun 21, 2014 at 05:32:44PM -0700, James Bottomley wrote: > > > No, we are not. Look: > > > * comparison promotes both operands to u64 here, so its result is > > > accurate, no matter how large count is. They are compared as natural > > > numbers. > > > > True ... figured this out 10 seconds after sending the email. > > > > > * assignment converts count to size_t, which *would* truncate for > > > values that are greater than the maximal value representable by size_t. > > > But in that case it's by definition greater than i->count, so we do not > > > reach that assignment at all. > > > > OK, so what I still don't get is why isn't the compiler warning when we > > truncate a u64 to a u32? We should get that warning in your new code, > > and we should have got that warning in fs/block_dev.c where it would > > have pinpointed the actual problem. > > In which universe? > > extern void f(unsigned int); > > void g(unsigned long x) > { > f(x); > } In the one where the code is compiled with -Wconversion ... I'm just surprised, I thought we had this enabled. James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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