On Mon, Mar 30, 2009 at 02:41:41PM -0500, Felix Blyakher wrote:
> The result of async io returned in the event.res in addition
> to the number of bytes read/written provides negated error
> number. The broken libaio defines event.res as unsigned
> while the same structure in the kernel defines it as signed.
> The kernel indeed treat it as signed, and returns the
> negated error number. Till libaio is fixed we provide
> the signed long temp var.
> Also set errno for each error condition in aio_rw, as the
> caller is not aio aware and expects ret(-1)+errno by the
> traditional libc convention.
>
> Signed-off-by: Felix Blyakher <felixb@xxxxxxx>
> ---
> ltp/fsx.c | 42 +++++++++++++++++++++++++++++++++++-------
> 1 files changed, 35 insertions(+), 7 deletions(-)
> if (len != event.res) {
> - fprintf(stderr, "bad read length: %lu instead of %u\n",
> - event.res, len);
> + /*
> + * The b0rked libaio defines event.res as unsigned.
> + * However the kernel strucuture has it signed,
> + * and it's used to pass negated error value.
> + * Till the library is fixed use the temp var.
> + */
> + res = (long)event.res;
> + if (res >= 0)
> + fprintf(stderr, "bad io length: %lu instead of %u\n",
> + res, len);
> + else {
> + fprintf(stderr, "errcode=%d\n", -res);
> + fprintf(stderr, "aio_rw: async io failed: %s\n",
> + strerror(-res));
> + goto out_error;
> + }
> +
> }
> return event.res;
> +
> +out_error:
> + /*
> + * The caller expects error return in traditional libc
> + * convention, i.e. -1 and the errno set to error.
> + */
> + errno = ret <= 0 ? -ret : -res;
> + return -1;
I wonder why this doesn't give a compiler warning. res is only
initialized in that last branch above. Wouldn't it be better to set
ret to res inside that branch and only use ret down here?
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