xen/blkback: simplify address translations

Cherry-pick and modified from 69d64727c42eecd47fdf82c15a54474d21a4012a
("blkback/blktap2: simplify address translations"):

"There are quite a number of places where e.g. page->va->page
translations happen.

Besides yielding smaller code (source and binary), a second goal is to
make it easier to determine where virtual addresses of pages allocated
through alloc_empty_pages_and_pagevec() are really used (in turn in
order to determine whether using highmem pages would be possible
there)."

The second goal is not the purpose of this patch - it is just to
make it easier to read the code.

linux-2.6-pvops:
 * Stripped drivers/xen/gntdev/*
 * Stripped drivers/xen/netback/*

[v2: Stripped blktap off]

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Daniel Stodden <daniel.stodden@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index cb844f7..7c9421c 100644 (file)
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -99,9 +99,11 @@ static inline int vaddr_pagenr(pending_req_t *req, int seg)
        return (req - pending_reqs) * BLKIF_MAX_SEGMENTS_PER_REQUEST + seg;
 }
 
+#define pending_page(req, seg) pending_pages[vaddr_pagenr(req, seg)]
+
 static inline unsigned long vaddr(pending_req_t *req, int seg)
 {
-       unsigned long pfn = page_to_pfn(pending_pages[vaddr_pagenr(req, seg)]);
+       unsigned long pfn = page_to_pfn(pending_page(req, seg));
        return (unsigned long)pfn_to_kaddr(pfn);
 }
 
@@ -463,8 +465,8 @@ static void dispatch_rw_block_io(blkif_t *blkif,
                if (ret)
                        continue;
 
-               set_phys_to_machine(__pa(vaddr(
-                       pending_req, i)) >> PAGE_SHIFT,
+               set_phys_to_machine(
+                       page_to_pfn(pending_page(pending_req, i)),
                        FOREIGN_FRAME(map[i].dev_bus_addr >> PAGE_SHIFT));
                seg[i].buf  = map[i].dev_bus_addr |
                        (req->seg[i].first_sect << 9);
@@ -495,7 +497,7 @@ static void dispatch_rw_block_io(blkif_t *blkif,
 
                while ((bio == NULL) ||
                       (bio_add_page(bio,
-                                    virt_to_page(vaddr(pending_req, i)),
+                                    pending_page(pending_req, i),
                                     seg[i].nsec << 9,
                                     seg[i].buf & ~PAGE_MASK) == 0)) {
                        if (bio) {