[PATCH resend] vfs: Add ->statfs callback for pipefs
xemul at parallels.com
Wed Aug 24 01:33:17 PDT 2011
> OK, I give up - how does it work?
> <goes off and reads the kernel>
> So it appears that the statfs call would previously return -ENOSYS, but
> with this change the statfs will succeed and userspace can then inspect
> f_type. Yes? I will fix your changelog by adding a description along these
Yes, the primary intention is to get the f_type.
> And I'll ask you to fix it further by telling us why we want to do
> this? The kernel has had this issue for a long time - why does it now
This is required by checkpoint-restart in the userspace to make it
possible to distinguish pipes from fifos. In more details:
When we dump information about task's open files we use the /proc/pid/fd
directoy's symlinks and the fact that opening any of them gives us exactly
the same dentry->inode pair as the original process has. Now if a task
we're dumping has opened pipe and fifo we need to detect this and act
accordingly. Knowing that an fd with type S_ISFIFO resides on a pipefs
is the most precise way.
More information about the Containers