linprocfs Input/output error

[Fernando Apesteguía]

2010/1/1 Jilles Tjoelker <jilles at stack.nl>:
> On Fri, Jan 01, 2010 at 06:45:33PM +0100, Fernando Apesteguía wrote:
>> Hi all, I post here cause I didn't get any answers in freebsd-emulation.
>
>> In 8.0-RELEASE-p1 if I try to execute this:
>
>> cat /compat/linux/proc/cpuinfo > ~/cpuinfo.txt
>
>> I get
>
>> cat: /compat/linux/proc/cpuinfo: Input/output error
>
>> truss shows the read system call returns ERR#5. It is the same with
>> other files from linprocfs.
>
>> cat /compat/linux/proc/[any_file] works fine
>
>> What am I missing?
>
> You are not missing anything, this is a bug. A while ago, cat(1) was
> changed to use larger buffers when writing to regular files on machines
> with sufficient RAM, usually a multiple of MAXPHYS. On the other hand,
> pseudofs (the general framework for filesystems such as procfs,
> linprocfs and linsysfs) in src/sys/fs/pseudofs/pseudofs_vnops.c
> pfs_read() fails any read over MAXPHYS + 1 with EIO. This limit probably
> has to do with the allocation of a buffer of that size using sbuf_new(9)
> (and so, malloc(9)).
>
> Some sort of limit seems appropriate, but MAXPHYS seems unrelated, and
> if the request is too long it should perhaps just truncate it.

Thanks a lot for the explanation.

>
> --
> Jilles Tjoelker
>