make consume_fd to return the fd it consumes

Signed-off-by: Thanos Makatos <thanos.makatos@nutanix.com>

3 files changed, 30 insertions, 12 deletions

diff --git a/lib/irq.c b/lib/irq.c
index e5c0b6d..9a4beff 100644
--- a/lib/irq.c
+++ b/lib/irq.c
@@ -171,9 +171,13 @@ irqs_set_data_eventfd(vfu_ctx_t *vfu_ctx, struct vfio_irq_set *irq_set,
 
             vfu_ctx->irqs->efds[i] = -1;
         }
-        if (data[j] >= 0) {
+        if (data[j] >= 0) { /* TODO IIUC this will always be >= 0? */
             vfu_ctx->irqs->efds[i] = data[j];
-            consume_fd(data, j);
+            /*
+             * We've already checked in handle_device_set_irqs that
+             * nr_fds == irq_set->count.
+             */
+            consume_fd(data, irq_set->count, j);
         }
         vfu_log(vfu_ctx, VFU_DBG, "event fd[%d]=%d", i, vfu_ctx->irqs->efds[i]);
     }
diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index a930258..e0b8465 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -500,10 +500,24 @@ handle_device_get_info(vfu_ctx_t *vfu_ctx, uint32_t size,
     return 0;
 }
 
+int
+consume_fd(int *fds, size_t nr_fds, size_t index)
+{
+   int fd;
+
+   if (index >= nr_fds) {
+       return -EINVAL;
+   }
+
+   fd = fds[index];
+   fds[index] = -1;
+   return fd;
+}
+
 void
-consume_fd(int *fds, size_t index)
+restore_fd(int *fds, size_t index, int fd)
 {
-    fds[index] = -1;
+    fds[index] = fd;
 }
 
 /*
@@ -549,11 +563,11 @@ handle_dma_map_or_unmap(vfu_ctx_t *vfu_ctx, uint32_t size, bool map,
         if (map) {
             int fd = -1;
             if (dma_regions[i].flags == VFIO_USER_F_DMA_REGION_MAPPABLE) {
-                if (fdi == nr_fds) {
-                    ret = -EINVAL;
+                fd = consume_fd(fds, nr_fds, fdi++);
+                if (fd < 0) {
+                    ret = fd;
                     break;
                 }
-                fd = fds[fdi];
             }
 
             ret = dma_controller_add_region(vfu_ctx->dma,
@@ -562,6 +576,9 @@ handle_dma_map_or_unmap(vfu_ctx_t *vfu_ctx, uint32_t size, bool map,
                                             fd,
                                             dma_regions[i].offset);
             if (ret < 0) {
+                if (fd != -1) {
+                    restore_fd(fds, fdi - 1, fd);
+                }
                 vfu_log(vfu_ctx, VFU_INF,
                         "failed to add DMA region %#lx-%#lx offset=%#lx fd=%d: %s",
                         dma_regions[i].addr,
@@ -570,9 +587,6 @@ handle_dma_map_or_unmap(vfu_ctx_t *vfu_ctx, uint32_t size, bool map,
                         strerror(-ret));
                 break;
             }
-            if (dma_regions[i].flags == VFIO_USER_F_DMA_REGION_MAPPABLE) {
-                consume_fd(fds, fdi++);
-            }
             vfu_log(vfu_ctx, VFU_DBG,
                     "added DMA region %#lx-%#lx offset=%#lx fd=%d",
                     dma_regions[i].addr,
diff --git a/lib/private.h b/lib/private.h
index 2753a20..a2fb3a7 100644
--- a/lib/private.h
+++ b/lib/private.h
@@ -163,8 +163,8 @@ exec_command(vfu_ctx_t *vfu_ctx, struct vfio_user_header *hdr, size_t size,
 int
 process_request(vfu_ctx_t *vfu_ctx);
 
-void
-consume_fd(int *fds, size_t index);
+int
+consume_fd(int *fds, size_t nr_fds, size_t index);
 
 #endif /* LIB_VFIO_USER_PRIVATE_H */