Commit 78270e8f authored Aug 14, 2014 by Weston Andros Adamson Committed by Trond Myklebust Aug 22, 2014

nfs: can_coalesce_requests must enforce contiguity



Commit 6094f838
"nfs: allow coalescing of subpage requests" got rid of the requirement
that requests cover whole pages, but it made some incorrect assumptions.

It turns out that callers of this interface can map adjacent requests
(by file position as seen by req_offset + req->wb_bytes) to different pages,
even when they could share a page. An example is the direct I/O interface -
iov_iter_get_pages_alloc may return one segment with a partial page filled
and the next segment (which is adjacent in the file position) starts with a
new page.

Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

parent bba5c188

fs/nfs/pagelist.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -823,6 +823,14 @@ static bool nfs_can_coalesce_requests(struct nfs_page *prev,
		return false;
		if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
		return false;
		if (req->wb_page == prev->wb_page) {
		if (req->wb_pgbase != prev->wb_pgbase + prev->wb_bytes)
		return false;
		} else {
		if (req->wb_pgbase != 0 \|\|
		prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
		return false;
		}
		}
		size = pgio->pg_ops->pg_test(pgio, prev, req);
		WARN_ON_ONCE(size > req->wb_bytes);

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