Currently the function will pointlessly acquire and release the global
'heap_lock' in this case.
NOTE: No caller yet calls domain_adjust_tot_pages() with a zero 'pages'
argument, but a subsequent patch will make this possible.
Signed-off-by: Paul Durrant <pdurr...@amazon.com>
---
Cc: Andrew Cooper <andrew.coop...@citrix.com>
Cc: George Dunlap <george.dun...@eu.citrix.com>
Cc: Ian Jackson <ian.jack...@eu.citrix.com>
Cc: Jan Beulich <jbeul...@suse.com>
Cc: Julien Grall <jul...@xen.org>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Stefano Stabellini <sstabell...@kernel.org>
Cc: Wei Liu <w...@xen.org>
v6:
- Modify memory_exchange()
v5:
- Split out from the subsequent 'make MEMF_no_refcount pages safe to
assign' patch as requested by Jan
---
xen/common/memory.c | 3 +--
xen/common/page_alloc.c | 3 +++
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/xen/common/memory.c b/xen/common/memory.c
index c7d2bac452..a4a5374d26 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -727,8 +727,7 @@ static long
memory_exchange(XEN_GUEST_HANDLE_PARAM(xen_memory_exchange_t) arg)
(j * (1UL << exch.out.extent_order)));
spin_lock(&d->page_alloc_lock);
- drop_dom_ref = (dec_count &&
- !domain_adjust_tot_pages(d, -dec_count));
+ drop_dom_ref = !domain_adjust_tot_pages(d, -dec_count);
spin_unlock(&d->page_alloc_lock);
if ( drop_dom_ref )
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 919a270587..135e15bae0 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -460,6 +460,9 @@ unsigned long domain_adjust_tot_pages(struct domain *d,
long pages)
{
long dom_before, dom_after, dom_claimed, sys_before, sys_after;
+ if ( !pages )
+ goto out;
+
ASSERT(spin_is_locked(&d->page_alloc_lock));
d->tot_pages += pages;
--
2.20.1
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