This is how vduse-blk.c does it, and it does seem better to have
dedicated functions for it.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
---
 block/export/fuse.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/block/export/fuse.c b/block/export/fuse.c
index bd98809d71..e50dd91d3e 100644
--- a/block/export/fuse.c
+++ b/block/export/fuse.c
@@ -78,6 +78,25 @@ static void read_from_fuse_export(void *opaque);
 static bool is_regular_file(const char *path, Error **errp);
 
 
+static void fuse_inc_in_flight(FuseExport *exp)
+{
+    if (qatomic_fetch_inc(&exp->in_flight) == 0) {
+        /* Prevent export from being deleted */
+        blk_exp_ref(&exp->common);
+    }
+}
+
+static void fuse_dec_in_flight(FuseExport *exp)
+{
+    if (qatomic_fetch_dec(&exp->in_flight) == 1) {
+        /* Wake AIO_WAIT_WHILE() */
+        aio_wait_kick();
+
+        /* Now the export can be deleted */
+        blk_exp_unref(&exp->common);
+    }
+}
+
 static void fuse_attach_handlers(FuseExport *exp)
 {
     aio_set_fd_handler(exp->common.ctx,
@@ -297,9 +316,7 @@ static void read_from_fuse_export(void *opaque)
     FuseExport *exp = opaque;
     int ret;
 
-    blk_exp_ref(&exp->common);
-
-    qatomic_inc(&exp->in_flight);
+    fuse_inc_in_flight(exp);
 
     do {
         ret = fuse_session_receive_buf(exp->fuse_session, &exp->fuse_buf);
@@ -317,11 +334,7 @@ static void read_from_fuse_export(void *opaque)
     fuse_session_process_buf(exp->fuse_session, &exp->fuse_buf);
 
 out:
-    if (qatomic_fetch_dec(&exp->in_flight) == 1) {
-        aio_wait_kick(); /* wake AIO_WAIT_WHILE() */
-    }
-
-    blk_exp_unref(&exp->common);
+    fuse_dec_in_flight(exp);
 }
 
 static void fuse_export_shutdown(BlockExport *blk_exp)
-- 
2.48.1

On Tue, Mar 25, 2025 at 05:06:49PM +0100, Hanna Czenczek wrote:
> This is how vduse-blk.c does it, and it does seem better to have
> dedicated functions for it.
> 
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
> ---
>  block/export/fuse.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>