file-posix: Move read/write operation logic out of aio_worker()

aio_worker() for reads and writes isn't boring enough yet. It still does
some postprocessing for handling short reads and turning the result into
the right return value.

However, there is no reason why handle_aiocb_rw() couldn't do the same,
and even without duplicating code between the read and write path. So
move the code there.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/file-posix.c

@@ -1311,7 +1311,8 @@ static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
          * we can just use plain pread/pwrite without any problems.
          */
         if (aiocb->io.niov == 1) {
-            return handle_aiocb_rw_linear(aiocb, aiocb->io.iov->iov_base);
+            nbytes = handle_aiocb_rw_linear(aiocb, aiocb->io.iov->iov_base);
+            goto out;
         }
         /*
          * We have more than one iovec, and all are properly aligned.
@@ -1323,7 +1324,7 @@ static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
             nbytes = handle_aiocb_rw_vector(aiocb);
             if (nbytes == aiocb->aio_nbytes ||
                 (nbytes < 0 && nbytes != -ENOSYS)) {
-                return nbytes;
+                goto out;
             }
             preadv_present = false;
         }
@@ -1341,7 +1342,8 @@ static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
      */
     buf = qemu_try_blockalign(aiocb->bs, aiocb->aio_nbytes);
     if (buf == NULL) {
-        return -ENOMEM;
+        nbytes = -ENOMEM;
+        goto out;
     }
 
     if (aiocb->aio_type & QEMU_AIO_WRITE) {
@@ -1375,7 +1377,21 @@ static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
     }
     qemu_vfree(buf);
 
-    return nbytes;
+out:
+    if (nbytes == aiocb->aio_nbytes) {
+        return 0;
+    } else if (nbytes >= 0 && nbytes < aiocb->aio_nbytes) {
+        if (aiocb->aio_type & QEMU_AIO_WRITE) {
+            return -EINVAL;
+        } else {
+            iov_memset(aiocb->io.iov, aiocb->io.niov, nbytes,
+                      0, aiocb->aio_nbytes - nbytes);
+            return 0;
+        }
+    } else {
+        assert(nbytes < 0);
+        return nbytes;
+    }
 }
 
 #ifdef CONFIG_XFS
@@ -1779,25 +1795,9 @@ static int aio_worker(void *arg)
     switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
     case QEMU_AIO_READ:
         ret = handle_aiocb_rw(aiocb);
-        if (ret >= 0 && ret < aiocb->aio_nbytes) {
-            iov_memset(aiocb->io.iov, aiocb->io.niov, ret,
-                      0, aiocb->aio_nbytes - ret);
-
-            ret = aiocb->aio_nbytes;
-        }
-        if (ret == aiocb->aio_nbytes) {
-            ret = 0;
-        } else if (ret >= 0 && ret < aiocb->aio_nbytes) {
-            ret = -EINVAL;
-        }
         break;
     case QEMU_AIO_WRITE:
         ret = handle_aiocb_rw(aiocb);
-        if (ret == aiocb->aio_nbytes) {
-            ret = 0;
-        } else if (ret >= 0 && ret < aiocb->aio_nbytes) {
-            ret = -EINVAL;
-        }
         break;
     case QEMU_AIO_IOCTL:
         ret = handle_aiocb_ioctl(aiocb);