Jan Beulich
2012-May-25 12:51 UTC
[PATCH 2/3] gnttab: mark maptrack free list tail with an explicit terminator
... instead of using the mutable current limit.
This also addresses an apparent off-by-one mistake when checking for
exhaustion of the maptrack table.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Andrew Thomas <andrew.thomas@oracle.com>
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -107,6 +107,8 @@ static unsigned inline int max_nr_maptra
return (max_nr_grant_frames * MAX_MAPTRACK_TO_GRANTS_RATIO);
}
+#define MAPTRACK_TAIL (~0u)
+
#define SHGNT_PER_PAGE_V1 (PAGE_SIZE / sizeof(grant_entry_v1_t))
#define shared_entry_v1(t, e) \
((t)->shared_v1[(e)/SHGNT_PER_PAGE_V1][(e)%SHGNT_PER_PAGE_V1])
@@ -198,7 +200,7 @@ __get_maptrack_handle(
struct grant_table *t)
{
unsigned int h;
- if ( unlikely((h = t->maptrack_head) == (t->maptrack_limit - 1)) )
+ if ( unlikely((h = t->maptrack_head) == MAPTRACK_TAIL) )
return -1;
t->maptrack_head = maptrack_entry(t, h).ref;
return h;
@@ -239,8 +241,10 @@ get_maptrack_handle(
new_mt_limit = lgt->maptrack_limit + MAPTRACK_PER_PAGE;
- for ( i = lgt->maptrack_limit; i < new_mt_limit; i++ )
- new_mt[i % MAPTRACK_PER_PAGE].ref = i + 1;
+ for ( i = 1; i < MAPTRACK_PER_PAGE; i++ )
+ new_mt[i - 1].ref = lgt->maptrack_limit + i;
+ new_mt[i - 1].ref = lgt->maptrack_head;
+ lgt->maptrack_head = lgt->maptrack_limit;
lgt->maptrack[nr_frames] = new_mt;
smp_wmb();
@@ -2577,9 +2581,10 @@ grant_table_create(
if ( (t->maptrack[0] = alloc_xenheap_page()) == NULL )
goto no_mem_3;
clear_page(t->maptrack[0]);
- t->maptrack_limit = PAGE_SIZE / sizeof(struct grant_mapping);
- for ( i = 0; i < t->maptrack_limit; i++ )
- t->maptrack[0][i].ref = i+1;
+ t->maptrack_limit = MAPTRACK_PER_PAGE;
+ for ( i = 1; i < MAPTRACK_PER_PAGE; i++ )
+ t->maptrack[0][i - 1].ref = i;
+ t->maptrack[0][i - 1].ref = MAPTRACK_TAIL;
/* Shared grant table. */
if ( (t->shared_raw = xzalloc_array(void *, max_nr_grant_frames)) ==
NULL )
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