[PATCH] block/file-posix: Limit max_iov to IOV_MAX

[lishan]

AIO read/write. The size of iocb->aio_nbytes in the kernel cannot exceed 
UIO_MAXIOV = 1024.
max_segments read from the block device layer may be greater than UIO_MAXIOV,
this causes the ioq_submit interface to return a -22(-EINVAL) error result.
---
 block/file-posix.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index d81e15efa4..27ab8d8784 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1273,7 +1273,8 @@ static void raw_refresh_limits(BlockDriverState *bs, 
Error **errp)
 
         ret = hdev_get_max_segments(s->fd, &st);
         if (ret > 0) {
-            bs->bl.max_iov = ret;
+            /* The maximum segment size allowed by the kernel is UIO_MAXIOV = 
1024. */
+            bs->bl.max_iov = MIN(ret, bs->bl.max_iov);
         }
     }
 }
-- 
2.19.1.windows.1