NFSv4.1: Fix an off-by-one error in pnfs_generic_pg_test
And document what is going on there...
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 0f42e02..29c0ca7 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1078,11 +1078,22 @@
return true;
}
- if (req_offset(req) > end_offset(pgio->pg_lseg->pls_range.offset,
- pgio->pg_lseg->pls_range.length))
- return false;
-
- return true;
+ /*
+ * Test if a nfs_page is fully contained in the pnfs_layout_range.
+ * Note that this test makes several assumptions:
+ * - that the previous nfs_page in the struct nfs_pageio_descriptor
+ * is known to lie within the range.
+ * - that the nfs_page being tested is known to be contiguous with the
+ * previous nfs_page.
+ * - Layout ranges are page aligned, so we only have to test the
+ * start offset of the request.
+ *
+ * Please also note that 'end_offset' is actually the offset of the
+ * first byte that lies outside the pnfs_layout_range. FIXME?
+ *
+ */
+ return req_offset(req) < end_offset(pgio->pg_lseg->pls_range.offset,
+ pgio->pg_lseg->pls_range.length);
}
EXPORT_SYMBOL_GPL(pnfs_generic_pg_test);