In swap_io() allocate the buffer before doing encryption.

If the allocation fails due to memory pressure no time is wasted doing
encryption.  This also simplify the error path.

Tested by sthen@.

ok kn@, miod@, kettenis@, tb@

diff --git a/sys/uvm/uvm_swap.c b/sys/uvm/uvm_swap.c
index 13e1e02..bee6ac9 100644 (file)
--- a/sys/uvm/uvm_swap.c
+++ b/sys/uvm/uvm_swap.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uvm_swap.c,v 1.153 2022/02/22 01:15:02 guenther Exp $ */
+/*     $OpenBSD: uvm_swap.c,v 1.154 2022/03/17 10:15:13 mpi Exp $      */
 /*     $NetBSD: uvm_swap.c,v 1.40 2000/11/17 11:39:39 mrg Exp $        */
 
 /*
@@ -1690,6 +1690,26 @@ uvm_swap_io(struct vm_page **pps, int startslot, int npages, int flags)
                }
        }
 
+       /*
+        * now allocate a buf for the i/o.
+        * [make sure we don't put the pagedaemon to sleep...]
+        */
+       pflag = (async || curproc == uvm.pagedaemon_proc) ? PR_NOWAIT :
+           PR_WAITOK;
+       bp = pool_get(&bufpool, pflag | PR_ZERO);
+
+       /*
+        * if we failed to get a swapbuf, return "try again"
+        */
+       if (bp == NULL) {
+               if (bounce) {
+                       uvm_pagermapout(bouncekva, npages);
+                       uvm_swap_freepages(tpps, npages);
+               }
+               uvm_pagermapout(kva, npages);
+               return (VM_PAGER_AGAIN);
+       }
+
        /* encrypt to swap */
        if (write && bounce) {
                int i, opages;
@@ -1731,35 +1751,6 @@ uvm_swap_io(struct vm_page **pps, int startslot, int npages, int flags)
                kva = bouncekva;
        }
 
-       /*
-        * now allocate a buf for the i/o.
-        * [make sure we don't put the pagedaemon to sleep...]
-        */
-       pflag = (async || curproc == uvm.pagedaemon_proc) ? PR_NOWAIT :
-           PR_WAITOK;
-       bp = pool_get(&bufpool, pflag | PR_ZERO);
-
-       /*
-        * if we failed to get a swapbuf, return "try again"
-        */
-       if (bp == NULL) {
-               if (write && bounce) {
-#ifdef UVM_SWAP_ENCRYPT
-                       int i;
-
-                       /* swap encrypt needs cleanup */
-                       if (encrypt)
-                               for (i = 0; i < npages; i++)
-                                       SWAP_KEY_PUT(sdp, SWD_KEY(sdp,
-                                           startslot + i));
-#endif
-
-                       uvm_pagermapout(kva, npages);
-                       uvm_swap_freepages(tpps, npages);
-               }
-               return (VM_PAGER_AGAIN);
-       }
-
        /*
         * prevent ASYNC reads.
         * uvm_swap_io is only called from uvm_swap_get, uvm_swap_get