[PATCH 1/2] memfd: add qemu_memfd_open()

[Marc-André Lureau]

Refactor qemu_memfd_alloc() to simply return the opened fd.

mmap() can be done later by the caller.

Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
 include/qemu/memfd.h |  3 +++
 util/memfd.c         | 39 +++++++++++++++++++++++++--------------
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
index 975b6bdb77..1642af9459 100644
--- a/include/qemu/memfd.h
+++ b/include/qemu/memfd.h
@@ -44,4 +44,7 @@ void *qemu_memfd_alloc(const char *name, size_t size, 
unsigned int seals,
 void qemu_memfd_free(void *ptr, size_t size, int fd);
 bool qemu_memfd_check(unsigned int flags);
 
+int qemu_memfd_open(const char *name, size_t size,
+                    unsigned int seals, Error **errp);
+
 #endif /* QEMU_MEMFD_H */
diff --git a/util/memfd.c b/util/memfd.c
index 4a3c07e0be..523b943b62 100644
--- a/util/memfd.c
+++ b/util/memfd.c
@@ -104,10 +104,9 @@ err:
  * memfd with sealing, but may fallback on other methods without
  * sealing.
  */
-void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
-                       int *fd, Error **errp)
+int qemu_memfd_open(const char *name, size_t size, unsigned int seals,
+                    Error **errp)
 {
-    void *ptr;
     int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
 
     /* some systems have memfd without sealing */
@@ -124,26 +123,38 @@ void *qemu_memfd_alloc(const char *name, size_t size, 
unsigned int seals,
         unlink(fname);
         g_free(fname);
 
-        if (mfd == -1 ||
-            ftruncate(mfd, size) == -1) {
-            goto err;
+        if (mfd != -1 && ftruncate(mfd, size) == -1) {
+            close(mfd);
+            mfd = -1;
         }
     }
 
+    if (mfd == -1) {
+        error_setg_errno(errp, errno, "qemu_memfd_open() failed");
+    }
+
+    return mfd;
+}
+
+void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
+                       int *fd, Error **errp)
+{
+    int mfd = qemu_memfd_open(name, size, seals, errp);
+    void *ptr;
+
+    if (mfd == -1) {
+        return NULL;
+    }
+
     ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
     if (ptr == MAP_FAILED) {
-        goto err;
+        error_setg_errno(errp, errno, "failed to allocate shared memory");
+        close(mfd);
+        return NULL;
     }
 
     *fd = mfd;
     return ptr;
-
-err:
-    error_setg_errno(errp, errno, "failed to allocate shared memory");
-    if (mfd >= 0) {
-        close(mfd);
-    }
-    return NULL;
 }
 
 void qemu_memfd_free(void *ptr, size_t size, int fd)
-- 
2.24.0