memfd: add error argument, instead of perror()

This will allow callers to silence error report when the call is
allowed to failed.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180201132757.23063-2-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/virtio/vhost.c

@@ -330,6 +330,7 @@ static uint64_t vhost_get_log_size(struct vhost_dev *dev)
 
 static struct vhost_log *vhost_log_alloc(uint64_t size, bool share)
 {
+    Error *err = NULL;
     struct vhost_log *log;
     uint64_t logsize = size * sizeof(*(log->log));
     int fd = -1;
@@ -338,7 +339,12 @@ static struct vhost_log *vhost_log_alloc(uint64_t size, bool share)
     if (share) {
         log->log = qemu_memfd_alloc("vhost-log", logsize,
                                     F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL,
-                                    &fd);
+                                    &fd, &err);
+        if (err) {
+            error_report_err(err);
+            g_free(log);
+            return NULL;
+        }
         memset(log->log, 0, logsize);
     } else {
         log->log = g_malloc0(logsize);

include/qemu/memfd.h

@@ -16,9 +16,10 @@
 #define F_SEAL_WRITE    0x0008  /* prevent writes */
 #endif
 
-int qemu_memfd_create(const char *name, size_t size, unsigned int seals);
+int qemu_memfd_create(const char *name, size_t size, unsigned int seals,
+                      Error **errp);
 void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
-                       int *fd);
+                       int *fd, Error **errp);
 void qemu_memfd_free(void *ptr, size_t size, int fd);
 bool qemu_memfd_check(void);
 

util/memfd.c

@@ -27,6 +27,7 @@
 
 #include "qemu/osdep.h"
 
+#include "qapi/error.h"
 #include "qemu/memfd.h"
 
 #if defined CONFIG_LINUX && !defined CONFIG_MEMFD
@@ -51,11 +52,11 @@ static int memfd_create(const char *name, unsigned int flags)
 #define MFD_ALLOW_SEALING 0x0002U
 #endif
 
-int qemu_memfd_create(const char *name, size_t size, unsigned int seals)
+int qemu_memfd_create(const char *name, size_t size,
+                      unsigned int seals, Error **errp)
 {
-    int mfd = -1;
-
 #ifdef CONFIG_LINUX
+    int mfd = -1;
     unsigned int flags = MFD_CLOEXEC;
 
     if (seals) {
@@ -64,23 +65,26 @@ int qemu_memfd_create(const char *name, size_t size, unsigned int seals)
 
     mfd = memfd_create(name, flags);
     if (mfd < 0) {
-        return -1;
+        goto err;
     }
 
     if (ftruncate(mfd, size) == -1) {
-        perror("ftruncate");
+        goto err;
-        close(mfd);
-        return -1;
     }
 
     if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
-        perror("fcntl");
+        goto err;
-        close(mfd);
-        return -1;
     }
-#endif
 
     return mfd;
+
+err:
+    if (mfd >= 0) {
+        close(mfd);
+    }
+#endif
+    error_setg_errno(errp, errno, "failed to create memfd");
+    return -1;
 }
 
 /*
@@ -90,14 +94,14 @@ int qemu_memfd_create(const char *name, size_t size, unsigned int seals)
  * sealing.
  */
 void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
-                       int *fd)
+                       int *fd, Error **errp)
 {
     void *ptr;
-    int mfd = qemu_memfd_create(name, size, seals);
+    int mfd = qemu_memfd_create(name, size, seals, NULL);
 
     /* some systems have memfd without sealing */
     if (mfd == -1) {
-        mfd = qemu_memfd_create(name, size, 0);
+        mfd = qemu_memfd_create(name, size, 0, NULL);
     }
 
     if (mfd == -1) {
@@ -109,27 +113,26 @@ void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
         unlink(fname);
         g_free(fname);
 
-        if (mfd == -1) {
+        if (mfd == -1 ||
-            perror("mkstemp");
+            ftruncate(mfd, size) == -1) {
-            return NULL;
+            goto err;
-        }
-
-        if (ftruncate(mfd, size) == -1) {
-            perror("ftruncate");
-            close(mfd);
-            return NULL;
         }
     }
 
     ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
     if (ptr == MAP_FAILED) {
-        perror("mmap");
+        goto err;
-        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)
@@ -157,7 +160,7 @@ bool qemu_memfd_check(void)
         int fd;
         void *ptr;
 
-        ptr = qemu_memfd_alloc("test", 4096, 0, &fd);
+        ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL);
         memfd_check = ptr ? MEMFD_OK : MEMFD_KO;
         qemu_memfd_free(ptr, 4096, fd);
     }