On Fri, Nov 01, 2013 at 10:35:42AM -0400, Tejun Heo wrote:
> Hello, Heiko.
>
> On Fri, Nov 01, 2013 at 03:13:48PM +0100, Heiko Carstens wrote:
> > before your patch it was like this:
> >
> > [pid 2888] open("/sys/class/net/eth0/broadcast", O_RDONLY) = 5
> > [pid 2888] lseek(5, 0, SEEK_END) = 4096
> > [pid 2888] lseek(5, 0, SEEK_SET) = 0
> > [pid 2888] read(5, "ff:ff:ff:ff:ff:ff\n", 4096) = 18
> > [pid 2888] close(5) = 0
> >
> > With your patch applied I get this:
> >
> > [pid 2450] open("/sys/class/net/eth0/broadcast", O_RDONLY) = 5
> > [pid 2450] lseek(5, 0, SEEK_END) = -1 EINVAL (Invalid argument)
> > [pid 2450] lseek(5, 0, SEEK_SET) = 0
> > [pid 2450] read(5, 0x557421e8, 4294967295) = -1 EINVAL (Invalid argument)
> > [pid 2450] close(5) = 0
> >
> > So the problem is that lseek with SEEK_END doesn't work.
> > Afterwards the process tried to use the return value of lseek as number of
> > bytes to be read, which doesn't work ;)
> >
> > This is a Fedora 17 like system on s390. It's a bit special since the kernel
> > is 64 bit and whole user space is 32 bit.
>
> LOL, that's creative. I guess we'll have to give up using
> seq_lseek(). Can you please test the following?
>
> Thanks.
>
> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> index 382db3c..79b5da2 100644
> --- a/fs/sysfs/file.c
> +++ b/fs/sysfs/file.c
> @@ -800,7 +800,7 @@ EXPORT_SYMBOL_GPL(sysfs_notify);
> const struct file_operations sysfs_file_operations = {
> .read = seq_read,
> .write = sysfs_write_file,
> - .llseek = seq_lseek,
> + .llseek = generic_file_llseek,
Does that mean that seq_lseek can't handle SEEK_END? Shouldn't we fix
that instead?
thanks,
greg k-h
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