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diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
--- a/sys/vm/swap_pager.c
+++ b/sys/vm/swap_pager.c
@@ -486,7 +486,8 @@
/*
* Metadata functions
*/
-static daddr_t swp_pager_meta_build(vm_object_t, vm_pindex_t, daddr_t);
+static daddr_t swp_pager_meta_build(vm_object_t, vm_pindex_t, daddr_t,
+ bool);
static void swp_pager_meta_free(vm_object_t, vm_pindex_t, vm_pindex_t,
vm_size_t *);
static void swp_pager_meta_transfer(vm_object_t src, vm_object_t dst,
@@ -1031,7 +1032,7 @@
}
for (j = 0; j < n; ++j) {
addr = swp_pager_meta_build(object,
- start + i + j, blk + j);
+ start + i + j, blk + j, false);
if (addr != SWAPBLK_NONE)
swp_pager_update_freerange(&range, addr);
}
@@ -1041,35 +1042,6 @@
return (0);
}
-static bool
-swp_pager_xfer_source(vm_object_t srcobject, vm_object_t dstobject,
- vm_pindex_t pindex, daddr_t addr)
-{
- daddr_t dstaddr __diagused;
-
- KASSERT((srcobject->flags & OBJ_SWAP) != 0,
- ("%s: srcobject not swappable", __func__));
- KASSERT((dstobject->flags & OBJ_SWAP) != 0,
- ("%s: dstobject not swappable", __func__));
-
- if (swp_pager_meta_lookup(dstobject, pindex) != SWAPBLK_NONE) {
- /* Caller should destroy the source block. */
- return (false);
- }
-
- /*
- * Destination has no swapblk and is not resident, transfer source.
- * swp_pager_meta_build() can sleep.
- */
- VM_OBJECT_WUNLOCK(srcobject);
- dstaddr = swp_pager_meta_build(dstobject, pindex, addr);
- KASSERT(dstaddr == SWAPBLK_NONE,
- ("Unexpected destination swapblk"));
- VM_OBJECT_WLOCK(srcobject);
-
- return (true);
-}
-
/*
* SWAP_PAGER_COPY() - copy blocks from source pager to destination pager
* and destroy the source.
@@ -1548,7 +1520,7 @@
mreq = ma[i + j];
vm_page_aflag_clear(mreq, PGA_SWAP_FREE);
addr = swp_pager_meta_build(mreq->object, mreq->pindex,
- blk + j);
+ blk + j, false);
if (addr != SWAPBLK_NONE)
swp_pager_update_freerange(&range, addr);
MPASS(mreq->dirty == VM_PAGE_BITS_ALL);
@@ -2052,16 +2024,22 @@
uma_zfree(swblk_zone, sb);
}
}
-
+
/*
* SWP_PAGER_META_BUILD() - add swap block to swap meta data for object
*
- * The specified swapblk is added to the object's swap metadata. If
- * the swapblk is not valid, it is freed instead. Any previously
- * assigned swapblk is returned.
+ * Try to add the specified swapblk to the object's swap metadata. If
+ * nowait_noreplace is set, add the specified swapblk only if there is no
+ * previously assigned swapblk at pindex. If the swapblk is invalid, and
+ * replaces a valid swapblk, empty swap metadata is freed. If memory
+ * allocation fails, and nowait_noreplace is set, return the specified
+ * swapblk immediately to indicate failure; otherwise, wait and retry until
+ * memory allocation succeeds. Return the previously assigned swapblk, if
+ * any.
*/
static daddr_t
-swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
+swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk,
+ bool nowait_noreplace)
{
static volatile int swblk_zone_exhausted, swpctrie_zone_exhausted;
struct swblk *sb, *sb1;
@@ -2088,6 +2066,8 @@
printf("swblk zone ok\n");
break;
}
+ if (nowait_noreplace)
+ return (swapblk);
VM_OBJECT_WUNLOCK(object);
if (uma_zone_exhausted(swblk_zone)) {
if (atomic_cmpset_int(&swblk_zone_exhausted,
@@ -2118,6 +2098,10 @@
printf("swpctrie zone ok\n");
break;
}
+ if (nowait_noreplace) {
+ uma_zfree(swblk_zone, sb);
+ return (swapblk);
+ }
VM_OBJECT_WUNLOCK(object);
if (uma_zone_exhausted(swpctrie_zone)) {
if (atomic_cmpset_int(&swpctrie_zone_exhausted,
@@ -2144,14 +2128,16 @@
modpi = pindex % SWAP_META_PAGES;
/* Return prior contents of metadata. */
prev_swapblk = sb->d[modpi];
- /* Enter block into metadata. */
- sb->d[modpi] = swapblk;
+ if (!nowait_noreplace || prev_swapblk == SWAPBLK_NONE) {
+ /* Enter block into metadata. */
+ sb->d[modpi] = swapblk;
- /*
- * Free the swblk if we end up with the empty page run.
- */
- if (swapblk == SWAPBLK_NONE)
- swp_pager_free_empty_swblk(object, sb);
+ /*
+ * Free the swblk if we end up with the empty page run.
+ */
+ if (swapblk == SWAPBLK_NONE)
+ swp_pager_free_empty_swblk(object, sb);
+ }
return (prev_swapblk);
}
@@ -2168,6 +2154,7 @@
{
struct page_range range;
struct swblk *sb;
+ daddr_t blk;
vm_page_t m;
vm_pindex_t offset, last;
vm_size_t mc;
@@ -2193,12 +2180,25 @@
limit = last - sb->p < SWAP_META_PAGES ? last - sb->p :
SWAP_META_PAGES;
for (i = start; i < limit; i++) {
- if (sb->d[i] == SWAPBLK_NONE)
+ blk = sb->d[i];
+ if (blk == SWAPBLK_NONE)
continue;
if (dstobject == NULL ||
- !swp_pager_xfer_source(srcobject, dstobject,
- sb->p + i - offset, sb->d[i])) {
+ (blk = swp_pager_meta_build(dstobject,
+ sb->p + i - offset, blk, true),
+ blk != sb->d[i] && blk != SWAPBLK_NONE))
swp_pager_update_freerange(&range, sb->d[i]);
+ else if (blk == sb->d[i]) {
+ /*
+ * Destination has no swapblk and is not
+ * resident, so transfer source.
+ * swp_pager_meta_build() failed memory
+ * allocation already, likely to sleep in retry.
+ */
+ VM_OBJECT_WUNLOCK(srcobject);
+ swp_pager_meta_build(dstobject,
+ sb->p + i - offset, blk, false);
+ VM_OBJECT_WLOCK(srcobject);
}
if (moved != NULL) {
if (m != NULL && m->pindex != pindex + i - 1)

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