Re: [PATCH v4 08/28] netfs: Provide readahead and readpage netfs helpers

[David Howells]

Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:

> > +	while ((page = readahead_page(ractl)))
> > +		put_page(page);
> 
> You don't need this pair of lines (unless I'm missing something).
> read_pages() in mm/readahead.c puts the reference and unlocks any
> pages which are not read by the readahead op.  Indeed, I think doing
> this is buggy because you don't unlock the page.

Actually, I do need them.  The pages haven't been removed from the ractl at
this point so just returning would cause them all to be unlocked prematurely.

I don't pass the ractl to the filesystem or the cache because I may be calling
them for partial pages, I may be issuing multiple ops sequentially on a page
and the ractl may have ceased to exist by the time I issue an op.

The unlocking is done by netfs_rreq_unlock(), even for pages that didn't get
read.

I've added a comment to this effect.

David