Q: a_ops->readpage() && struct file

[Peter Zijlstra]

On Mon, 2012-06-11 at 21:09 +0200, Oleg Nesterov wrote:
> Stupid question. I'm afraid the answer is "no" but I'll ask anyway.
> Is it safe to pass filp == NULL to mapping->readpage()? In fact
> I do not understand why it needs "struct file*" and I do not see
> any example of actual usage. 

Looking at afs_readpage it looks like its OK to pass in NULL. Same for
nfs_readpage. They use the file, if provided, to avoid some lookups, but
seem to deal with not having it.

This answer by example is of course not authorative nor complete.