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xen_disk: fix unmapping of persistent grants

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This patch fixes two issues with persistent grants and the disk PV backend
(Qdisk):

 - Keep track of memory regions where persistent grants have been mapped
   since we need to unmap them as a whole. It is not possible to unmap a
   single grant if it has been batch-mapped. A new check has also been added
   to make sure persistent grants are only used if the whole mapped region
   can be persistently mapped in the batch_maps case.
 - Unmap persistent grants before switching to the closed state, so the
   frontend can also free them.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reported-by: George Dunlap <george.dunlap@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Roger Pau Monne 2014-11-13 18:42:09 +01:00 committed by Stefano Stabellini
parent 91ab2ed722
commit 2f01dfacb5
1 changed files with 66 additions and 6 deletions
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72
hw/block/xen_disk.c
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@ -59,6 +59,13 @@ struct PersistentGrant {
typedef struct PersistentGrant PersistentGrant;
struct PersistentRegion {
void *addr;
int num;
};
typedef struct PersistentRegion PersistentRegion;
struct ioreq {
blkif_request_t req;
int16_t status;
@ -118,6 +125,7 @@ struct XenBlkDev {
gboolean feature_discard;
gboolean feature_persistent;
GTree *persistent_gnts;
GSList *persistent_regions;
unsigned int persistent_gnt_count;
unsigned int max_grants;
@ -177,6 +185,23 @@ static void destroy_grant(gpointer pgnt)
g_free(grant);
}
static void remove_persistent_region(gpointer data, gpointer dev)
{
PersistentRegion *region = data;
struct XenBlkDev *blkdev = dev;
XenGnttab gnt = blkdev->xendev.gnttabdev;
if (xc_gnttab_munmap(gnt, region->addr, region->num) != 0) {
xen_be_printf(&blkdev->xendev, 0,
"xc_gnttab_munmap region %p failed: %s\n",
region->addr, strerror(errno));
}
xen_be_printf(&blkdev->xendev, 3,
"unmapped grant region %p with %d pages\n",
region->addr, region->num);
g_free(region);
}
static struct ioreq *ioreq_start(struct XenBlkDev *blkdev)
{
struct ioreq *ioreq = NULL;
@ -343,6 +368,7 @@ static int ioreq_map(struct ioreq *ioreq)
void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST];
int i, j, new_maps = 0;
PersistentGrant *grant;
PersistentRegion *region;
/* domids and refs variables will contain the information necessary
* to map the grants that are needed to fulfill this request.
*
@ -421,7 +447,22 @@ static int ioreq_map(struct ioreq *ioreq)
}
}
}
if (ioreq->blkdev->feature_persistent) {
if (ioreq->blkdev->feature_persistent && new_maps != 0 &&
(!batch_maps || (ioreq->blkdev->persistent_gnt_count + new_maps <=
ioreq->blkdev->max_grants))) {
/*
* If we are using persistent grants and batch mappings only
* add the new maps to the list of persistent grants if the whole
* area can be persistently mapped.
*/
if (batch_maps) {
region = g_malloc0(sizeof(*region));
region->addr = ioreq->pages;
region->num = new_maps;
ioreq->blkdev->persistent_regions = g_slist_append(
ioreq->blkdev->persistent_regions,
region);
}
while ((ioreq->blkdev->persistent_gnt_count < ioreq->blkdev->max_grants)
&& new_maps) {
/* Go through the list of newly mapped grants and add as many
@ -447,6 +488,7 @@ static int ioreq_map(struct ioreq *ioreq)
grant);
ioreq->blkdev->persistent_gnt_count++;
}
assert(!batch_maps || new_maps == 0);
}
for (i = 0; i < ioreq->v.niov; i++) {
ioreq->v.iov[i].iov_base += (uintptr_t)page[i];
@ -971,7 +1013,10 @@ static int blk_connect(struct XenDevice *xendev)
blkdev->max_grants = max_requests * BLKIF_MAX_SEGMENTS_PER_REQUEST;
blkdev->persistent_gnts = g_tree_new_full((GCompareDataFunc)int_cmp,
NULL, NULL,
batch_maps ?
(GDestroyNotify)g_free :
(GDestroyNotify)destroy_grant);
blkdev->persistent_regions = NULL;
blkdev->persistent_gnt_count = 0;
}
@ -1000,6 +1045,26 @@ static void blk_disconnect(struct XenDevice *xendev)
blkdev->cnt_map--;
blkdev->sring = NULL;
}
/*
* Unmap persistent grants before switching to the closed state
* so the frontend can free them.
*
* In the !batch_maps case g_tree_destroy will take care of unmapping
* the grant, but in the batch_maps case we need to iterate over every
* region in persistent_regions and unmap it.
*/
if (blkdev->feature_persistent) {
g_tree_destroy(blkdev->persistent_gnts);
assert(batch_maps || blkdev->persistent_gnt_count == 0);
if (batch_maps) {
blkdev->persistent_gnt_count = 0;
g_slist_foreach(blkdev->persistent_regions,
(GFunc)remove_persistent_region, blkdev);
g_slist_free(blkdev->persistent_regions);
}
blkdev->feature_persistent = false;
}
}
static int blk_free(struct XenDevice *xendev)
@ -1011,11 +1076,6 @@ static int blk_free(struct XenDevice *xendev)
blk_disconnect(xendev);
}
/* Free persistent grants */
if (blkdev->feature_persistent) {
g_tree_destroy(blkdev->persistent_gnts);
}
while (!QLIST_EMPTY(&blkdev->freelist)) {
ioreq = QLIST_FIRST(&blkdev->freelist);
QLIST_REMOVE(ioreq, list);