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SubjectRe: lseek() on debugfs entries in 2.6.37
Date
On Tuesday 15 March 2011, Alexey Mikhailov wrote:
> I use simple debugfs entries for user-space <-> kernel-space
> interaction. Basically I read unsigned integers from debugfs
> files like this:
>
> ...
> char buf[64];
> lseek(timesync_fd, 0, SEEK_SET);
> read(timesync_fd, buf, sizeof(buf));
> ...
>
> It works perfectly with 2.6.32 kernel. But with 2.6.37 kernel,
> lseek() fails with errno=29(Illegal seek). So second read()
> call just fails or returns garbage. Can someone please shed
> some light on it?

This is probably a result of the changes I made as part of the
BKL removal. Which file specifically are you talking about?

In older kernels, having no .llseek function meant that you
implicitly get default_llseek. New kernels now require
that the driver explicitly chooses one llseek variant.

I did a patch to automatically convert all drivers, but
this patch may have missed some that got moved around
while I was patching them.

Arnd


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