[PATCH RFC 11/12] xen-blkback: expand map/unmap functions

From: Roger Pau Monne
Date: Thu Feb 28 2013 - 05:30:15 EST

Preparatory change for implementing indirect descriptors. Change
xen_blkbk_{map/unmap} in order to be able to map/unmap a random amount
of grants (previously it was limited to
BLKIF_MAX_SEGMENTS_PER_REQUEST). Also, remove the usage of pending_req
in the map/unmap functions, so we can map/unmap grants without needing
to pass a pending_req.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxx
---
drivers/block/xen-blkback/blkback.c | 134 ++++++++++++++++++++++-------------
1 files changed, 85 insertions(+), 49 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 04ad2aa..0fa30db 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -178,10 +178,6 @@ static inline void remove_free_pages(struct xen_blkif *blkif, int num)

#define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))

-#define pending_handle(_req, _seg) \
- (_req->grant_handles[_seg])
-
-
static int do_block_io_op(struct xen_blkif *blkif);
static int dispatch_rw_block_io(struct xen_blkif *blkif,
struct blkif_request *req,
@@ -590,53 +586,60 @@ struct seg_buf {
* Unmap the grant references, and also remove the M2P over-rides
* used in the 'pending_req'.
*/
-static void xen_blkbk_unmap(struct pending_req *req)
+static void xen_blkbk_unmap(struct xen_blkif *blkif,
+ grant_handle_t handles[],
+ struct page *pages[],
+ struct persistent_gnt *persistent_gnts[],
+ int num)
{
struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
- struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+ struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct persistent_gnt *persistent_gnt;
unsigned int i, invcount = 0;
- grant_handle_t handle;
- struct xen_blkif *blkif = req->blkif;
int ret;

- for (i = 0; i < req->nr_pages; i++) {
- if (req->persistent_gnts[i] != NULL) {
- persistent_gnt = req->persistent_gnts[i];
+ for (i = 0; i < num; i++) {
+ if (persistent_gnts[i] != NULL) {
+ persistent_gnt = persistent_gnts[i];
persistent_gnt->flags |= PERSISTENT_GNT_USED;
persistent_gnt->flags &= ~PERSISTENT_GNT_ACTIVE;
continue;
}
- handle = pending_handle(req, i);
- pages[invcount] = req->pages[i];
- if (handle == BLKBACK_INVALID_HANDLE)
+ if (handles[i] == BLKBACK_INVALID_HANDLE)
continue;
- gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[invcount]),
- GNTMAP_host_map, handle);
- pending_handle(req, i) = BLKBACK_INVALID_HANDLE;
- invcount++;
+ unmap_pages[invcount] = pages[i];
+ gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]),
+ GNTMAP_host_map, handles[i]);
+ handles[i] = BLKBACK_INVALID_HANDLE;
+ if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
+ ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
+ invcount);
+ BUG_ON(ret);
+ put_free_pages(blkif, unmap_pages, invcount);
+ invcount = 0;
+ }
+ }
+ if (invcount) {
+ ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
+ BUG_ON(ret);
+ put_free_pages(blkif, unmap_pages, invcount);
}
-
- ret = gnttab_unmap_refs(unmap, NULL, pages, invcount);
- BUG_ON(ret);
- put_free_pages(blkif, pages, invcount);
}

-static int xen_blkbk_map(struct blkif_request *req,
- struct pending_req *pending_req,
- struct seg_buf seg[],
- struct page *pages[])
+static int xen_blkbk_map(struct xen_blkif *blkif, grant_ref_t grefs[],
+ struct persistent_gnt *persistent_gnts[],
+ grant_handle_t handles[],
+ struct page *pages[],
+ int num, bool ro)
{
struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
- struct persistent_gnt **persistent_gnts = pending_req->persistent_gnts;
struct persistent_gnt *persistent_gnt = NULL;
- struct xen_blkif *blkif = pending_req->blkif;
phys_addr_t addr = 0;
int i, j;
- int nseg = req->u.rw.nr_segments;
int segs_to_map = 0;
int ret = 0;
+ int last_map = 0, map_until = 0;
int use_persistent_gnts;

use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
@@ -646,13 +649,14 @@ static int xen_blkbk_map(struct blkif_request *req,
* assign map[..] with the PFN of the page in our domain with the
* corresponding grant reference for each page.
*/
- for (i = 0; i < nseg; i++) {
+again:
+ for (i = map_until; i < num; i++) {
uint32_t flags;

if (use_persistent_gnts)
persistent_gnt = get_persistent_gnt(
&blkif->persistent_gnts,
- req->u.rw.seg[i].gref);
+ grefs[i]);

if (persistent_gnt) {
/*
@@ -669,13 +673,15 @@ static int xen_blkbk_map(struct blkif_request *req,
pages_to_gnt[segs_to_map] = pages[i];
persistent_gnts[i] = NULL;
flags = GNTMAP_host_map;
- if (!use_persistent_gnts &&
- (pending_req->operation != BLKIF_OP_READ))
+ if (!use_persistent_gnts && ro)
flags |= GNTMAP_readonly;
gnttab_set_map_op(&map[segs_to_map++], addr,
- flags, req->u.rw.seg[i].gref,
+ flags, grefs[i],
blkif->domid);
}
+ map_until = i + 1;
+ if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
+ break;
}

if (segs_to_map) {
@@ -688,22 +694,20 @@ static int xen_blkbk_map(struct blkif_request *req,
* so that when we access vaddr(pending_req,i) it has the contents of
* the page from the other domain.
*/
- for (i = 0, j = 0; i < nseg; i++) {
+ for (i = last_map, j = 0; i < map_until; i++) {
if (!persistent_gnts[i]) {
/* This is a newly mapped grant */
BUG_ON(j >= segs_to_map);
if (unlikely(map[j].status != 0)) {
pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
- pending_handle(pending_req, i) =
- BLKBACK_INVALID_HANDLE;
+ handles[i] = BLKBACK_INVALID_HANDLE;
ret |= 1;
- j++;
- continue;
+ goto next;
}
- pending_handle(pending_req, i) = map[j].handle;
+ handles[i] = map[j].handle;
}
if (persistent_gnts[i])
- goto next;
+ continue;
if (use_persistent_gnts &&
blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
/*
@@ -718,7 +722,6 @@ static int xen_blkbk_map(struct blkif_request *req,
* allocate the persistent_gnt struct
* map this grant non-persistenly
*/
- j++;
goto next;
}
persistent_gnt->gnt = map[j].ref;
@@ -735,7 +738,6 @@ static int xen_blkbk_map(struct blkif_request *req,
pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n",
persistent_gnt->gnt, blkif->persistent_gnt_c,
xen_blkif_max_pgrants);
- j++;
goto next;
}
if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
@@ -743,11 +745,14 @@ static int xen_blkbk_map(struct blkif_request *req,
pr_debug(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n",
blkif->domid, blkif->vbd.handle);
}
- j++;
next:
- seg[i].buf = pfn_to_mfn(page_to_pfn(pages[i])) << PAGE_SHIFT |
- (req->u.rw.seg[i].first_sect << 9);
+ j++;
}
+ segs_to_map = 0;
+ last_map = map_until;
+ if (map_until != num)
+ goto again;
+
return ret;

out_of_memory:
@@ -756,6 +761,32 @@ out_of_memory:
return -ENOMEM;
}

+static int xen_blkbk_map_seg(struct blkif_request *req,
+ struct pending_req *pending_req,
+ struct seg_buf seg[],
+ struct page *pages[])
+{
+ int i, rc;
+ grant_ref_t grefs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+
+ for (i = 0; i < req->u.rw.nr_segments; i++)
+ grefs[i] = req->u.rw.seg[i].gref;
+
+ rc = xen_blkbk_map(pending_req->blkif, grefs,
+ pending_req->persistent_gnts,
+ pending_req->grant_handles, pending_req->pages,
+ req->u.rw.nr_segments,
+ (pending_req->operation != BLKIF_OP_READ));
+ if (rc)
+ return rc;
+
+ for (i = 0; i < req->u.rw.nr_segments; i++)
+ seg[i].buf = pfn_to_mfn(page_to_pfn(pending_req->pages[i]))
+ << PAGE_SHIFT | (req->u.rw.seg[i].first_sect << 9);
+
+ return 0;
+}
+
static int dispatch_discard_io(struct xen_blkif *blkif,
struct blkif_request *req)
{
@@ -832,7 +863,10 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
* the proper response on the ring.
*/
if (atomic_dec_and_test(&pending_req->pendcnt)) {
- xen_blkbk_unmap(pending_req);
+ xen_blkbk_unmap(pending_req->blkif, pending_req->grant_handles,
+ pending_req->pages,
+ pending_req->persistent_gnts,
+ pending_req->nr_pages);
make_response(pending_req->blkif, pending_req->id,
pending_req->operation, pending_req->status);
xen_blkif_put(pending_req->blkif);
@@ -1040,7 +1074,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
* the hypercall to unmap the grants - that is all done in
* xen_blkbk_unmap.
*/
- if (xen_blkbk_map(req, pending_req, seg, pages))
+ if (xen_blkbk_map_seg(req, pending_req, seg, pages))
goto fail_flush;

/*
@@ -1107,7 +1141,9 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
return 0;

fail_flush:
- xen_blkbk_unmap(pending_req);
+ xen_blkbk_unmap(blkif, pending_req->grant_handles,
+ pending_req->pages, pending_req->persistent_gnts,
+ pending_req->nr_pages);
fail_response:
/* Haven't submitted any bio's yet. */
make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
--
1.7.7.5 (Apple Git-26)

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