Fix issue preventing using splice with reads (#505)

Context: SPLICE_WRITE is not used with regular buffers
(i.e. when they are not file-descriptor backed buffers).
There is a bug which assumes file descriptors are used.
If the amount of data associated with those FD is lower
than twice the page size, SPLICE_WRITE is not utilized.
With regular buffers the aggregated size was always 0.
Because vmsplice (splice user pages to/from a pipe) is
called before splice in fuse_lowlevel.c, regular buffers
would also work with splice.

This patch prevents to fallback to non-splice enabled
copies when itheir is no FD involved.

diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index d8112f5854535519358309bf89c83633bd002dea..fd1f484e64b81b979cd3dc7b1328703b8a063ab0 100644 (file)
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -650,7 +650,7 @@ static int fuse_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
        struct fuse_ll_pipe *llp;
        int splice_flags;
        size_t pipesize;
-       size_t total_fd_size;
+       size_t total_buf_size;
        size_t idx;
        size_t headerlen;
        struct fuse_bufvec pipe_buf = FUSE_BUFVEC_INIT(len);
@@ -661,15 +661,13 @@ static int fuse_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
        if (flags & FUSE_BUF_NO_SPLICE)
                goto fallback;
 
-       total_fd_size = 0;
+       total_buf_size = 0;
        for (idx = buf->idx; idx < buf->count; idx++) {
-               if (buf->buf[idx].flags & FUSE_BUF_IS_FD) {
-                       total_fd_size = buf->buf[idx].size;
-                       if (idx == buf->idx)
-                               total_fd_size -= buf->off;
-               }
+               total_buf_size = buf->buf[idx].size;
+               if (idx == buf->idx)
+                       total_buf_size -= buf->off;
        }
-       if (total_fd_size < 2 * pagesize)
+       if (total_buf_size < 2 * pagesize)
                goto fallback;
 
        if (se->conn.proto_minor < 14 ||