Re: [RESEND] [PATCH] VFS: make file->f_pos access atomic on 32bit arch

Matthew Wilcox
2008-10-08T05:16:43Z

On Wed, Oct 08, 2008 at 01:48:10PM +0900, Hisashi Hifumi wrote:
> Simultaneous access by two or more writer can corrupt file content,
> so this case needs some locks(flock or fcntl) to preserve synchronization
> of file content. This is responsibility of user-space application.
> But file->f_pos race issue can occur even if multiple threads just read
> simultaneously. I think this is not responsibility of user-space application.
> To avoid this currently, an application needs some locks to protect file offset
> even if it just read a file. So I think f_pos race should be fixed.

Why is this application not using pread() / pwrite() to use thread-local
file pointers?

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."