[PATCH v3 14/21] fuse: Reduce max read size

[Hanna Czenczek <hreitz@redhat.com>]

We are going to introduce parallel processing via coroutines, a maximum
read size of 64 MB may be problematic, allowing users of the export to
force us to allocate quite large amounts of memory with just a few
requests.

At least tone it down to 1 MB, which is still probably far more than
enough.  (Larger requests are split automatically by the FUSE kernel
driver anyway.)

(Yes, we inadvertently already had parallel request processing due to
nested polling before.  Better to fix this late than never.)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
---
 block/export/fuse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/export/fuse.c b/block/export/fuse.c
index 85ebc6bda8..8ea590ba67 100644
--- a/block/export/fuse.c
+++ b/block/export/fuse.c
@@ -45,7 +45,7 @@
 #endif
 
 /* Prevent overly long bounce buffer allocations */
-#define FUSE_MAX_READ_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 64 * 1024 * 1024))
+#define FUSE_MAX_READ_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 1 * 1024 * 1024))
 /* Small enough to fit in the request buffer */
 #define FUSE_MAX_WRITE_BYTES (4 * 1024)
 
-- 
2.49.0