diff mbox series

[1/2] tools/migration: Fix iovec handling in send_checkpoint_dirty_pfn_list()

Message ID 20210706112332.31753-2-andrew.cooper3@citrix.com (mailing list archive)
State New, archived
Headers show
Series tools/migration: Fixes in send_checkpoint_dirty_pfn_list() | expand

Commit Message

Andrew Cooper July 6, 2021, 11:23 a.m. UTC 
We shouldn't be using two struct iovec's to write half of 'rec' each, and
there is no need to malloc() for two struct iovec's at all.

Simplify down to just two - one covering the whole of 'rec', and one covering
the pfns array.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Ian Jackson <iwj@xenproject.org>
CC: Wei Liu <wl@xen.org>
CC: Juergen Gross <jgross@suse.com>
CC: Jan Beulich <JBeulich@suse.com>
CC: Olaf Hering <olaf@aepfle.de>
---
 tools/libs/guest/xg_sr_restore.c | 25 ++++++-------------------
 1 file changed, 6 insertions(+), 19 deletions(-)

Comments

Jan Beulich July 6, 2021, 11:54 a.m. UTC | #1 
On 06.07.2021 13:23, Andrew Cooper wrote:
> We shouldn't be using two struct iovec's to write half of 'rec' each, and
> there is no need to malloc() for two struct iovec's at all.

I was indeed wondering about all of these while also touching the
function. But I was guessing that there might be a deeper reason I
don't see.

> Simplify down to just two - one covering the whole of 'rec', and one covering
> the pfns array.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan
Olaf Hering July 6, 2021, 12:20 p.m. UTC | #2 
Am Tue, 6 Jul 2021 12:23:31 +0100
schrieb Andrew Cooper <andrew.cooper3@citrix.com>:

> We shouldn't be using two struct iovec's to write half of 'rec' each, and
> there is no need to malloc() for two struct iovec's at all.
> 
> Simplify down to just two - one covering the whole of 'rec', and one covering
> the pfns array.

Acked-by: Olaf Hering <olaf@aepfle.de>


Olaf
diff mbox series

Patch

diff --git a/tools/libs/guest/xg_sr_restore.c b/tools/libs/guest/xg_sr_restore.c
index aa4113d7f679..07c9e291610b 100644
--- a/tools/libs/guest/xg_sr_restore.c
+++ b/tools/libs/guest/xg_sr_restore.c
@@ -425,11 +425,13 @@  static int send_checkpoint_dirty_pfn_list(struct xc_sr_context *ctx)
     int rc = -1;
     unsigned int count, written;
     uint64_t i, *pfns = NULL;
-    struct iovec *iov = NULL;
     xc_shadow_op_stats_t stats = { 0, ctx->restore.p2m_size };
     struct xc_sr_record rec = {
         .type = REC_TYPE_CHECKPOINT_DIRTY_PFN_LIST,
     };
+    struct iovec iov[2] = {
+        { &rec, sizeof(rec) },
+    };
     DECLARE_HYPERCALL_BUFFER_SHADOW(unsigned long, dirty_bitmap,
                                     &ctx->restore.dirty_bitmap_hbuf);
 
@@ -471,26 +473,12 @@  static int send_checkpoint_dirty_pfn_list(struct xc_sr_context *ctx)
         pfns[written++] = i;
     }
 
-    /* iovec[] for writev(). */
-    iov = malloc(3 * sizeof(*iov));
-    if ( !iov )
-    {
-        ERROR("Unable to allocate memory for sending dirty bitmap");
-        goto err;
-    }
-
     rec.length = count * sizeof(*pfns);
 
-    iov[0].iov_base = &rec.type;
-    iov[0].iov_len = sizeof(rec.type);
-
-    iov[1].iov_base = &rec.length;
-    iov[1].iov_len = sizeof(rec.length);
-
-    iov[2].iov_base = pfns;
-    iov[2].iov_len = count * sizeof(*pfns);
+    iov[1].iov_base = pfns;
+    iov[1].iov_len = rec.length;
 
-    if ( writev_exact(ctx->restore.send_back_fd, iov, 3) )
+    if ( writev_exact(ctx->restore.send_back_fd, iov, ARRAY_SIZE(iov)) )
     {
         PERROR("Failed to write dirty bitmap to stream");
         goto err;
@@ -499,7 +487,6 @@  static int send_checkpoint_dirty_pfn_list(struct xc_sr_context *ctx)
     rc = 0;
  err:
     free(pfns);
-    free(iov);
     return rc;
 }