Matthew Wilcox [off-list ref] wrote:

quoted

+	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