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

Oleg Nesterov oleg at redhat.com
Thu Jun 14 05:19:28 EST 2012

On 06/13, Peter Zijlstra wrote:
> 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.

Yes, and reiser4 does the same.

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

Yes... perhaps we should simply change this code to use NULL and
collect the bug-reports ;)


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