splice engine: add unmapping for vmsplice-to-user

[fio.git] / engines / splice.c

diff --git a/engines/splice.c b/engines/splice.c
index b92da4a85577d1d945b354699861ff412ef6b1d7..d8080b42ff71460b8a340dd858da795f5a8511a6 100644 (file)
--- a/engines/splice.c
+++ b/engines/splice.c
@@ -18,14 +18,15 @@
 
 struct spliceio_data {
        int pipe[2];
+       int vmsplice_to_user;
 };
 
 /*
- * For splice reading, we unfortunately cannot (yet) vmsplice the other way.
- * So just splice the data from the file into the pipe, and use regular
- * read to fill the buffer. Doesn't make a lot of sense, but...
+ * vmsplice didn't use to support splicing to user space, this is the old
+ * variant of getting that job done. Doesn't make a lot of sense, but it
+ * uses splices to move data from the source into a pipe.
  */
-static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
+static int fio_splice_read_old(struct thread_data *td, struct io_u *io_u)
 {
        struct spliceio_data *sd = td->io_ops->data;
        struct fio_file *f = io_u->file;
@@ -65,6 +66,60 @@ static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
        return io_u->xfer_buflen;
 }
 
+/*
+ * We can now vmsplice into userspace, so do the transfer by splicing into
+ * a pipe and vmsplicing that into userspace.
+ */
+static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
+{
+       struct spliceio_data *sd = td->io_ops->data;
+       struct fio_file *f = io_u->file;
+       struct iovec iov;
+       int ret, buflen;
+       off_t offset;
+       void *p;
+
+       offset = io_u->offset;
+       buflen = io_u->xfer_buflen;
+       p = io_u->xfer_buf;
+       io_u->xfer_buf = NULL;
+       while (buflen) {
+               int this_len = buflen;
+
+               if (this_len > SPLICE_DEF_SIZE)
+                       this_len = SPLICE_DEF_SIZE;
+
+               ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len, SPLICE_F_MORE);
+               if (ret < 0) {
+                       if (errno == ENODATA || errno == EAGAIN)
+                               continue;
+
+                       return -errno;
+               }
+
+               buflen -= ret;
+               iov.iov_base = p;
+               iov.iov_len = ret;
+               p += ret;
+
+               while (iov.iov_len) {
+                       ret = vmsplice(sd->pipe[0], &iov, 1, SPLICE_F_MOVE);
+                       if (ret < 0)
+                               return -errno;
+                       else if (!ret)
+                               return -ENODATA;
+
+                       if (!io_u->xfer_buf)
+                               io_u->xfer_buf = iov.iov_base;
+                       iov.iov_len -= ret;
+                       iov.iov_base += ret;
+               }
+       }
+
+       io_u->unmap = splice_unmap_io_u;
+       return io_u->xfer_buflen;
+}
+
 /*
  * For splice writing, we can vmsplice our data buffer directly into a
  * pipe and then splice that to a file.
@@ -72,27 +127,25 @@ static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
 static int fio_splice_write(struct thread_data *td, struct io_u *io_u)
 {
        struct spliceio_data *sd = td->io_ops->data;
-       struct iovec iov[1] = {
-               {
-                       .iov_base = io_u->xfer_buf,
-                       .iov_len = io_u->xfer_buflen,
-               }
+       struct iovec iov = {
+               .iov_base = io_u->xfer_buf,
+               .iov_len = io_u->xfer_buflen,
        };
        struct pollfd pfd = { .fd = sd->pipe[1], .events = POLLOUT, };
        struct fio_file *f = io_u->file;
        off_t off = io_u->offset;
        int ret, ret2;
 
-       while (iov[0].iov_len) {
+       while (iov.iov_len) {
                if (poll(&pfd, 1, -1) < 0)
                        return errno;
 
-               ret = vmsplice(sd->pipe[1], iov, 1, SPLICE_F_NONBLOCK);
+               ret = vmsplice(sd->pipe[1], &iov, 1, SPLICE_F_NONBLOCK);
                if (ret < 0)
                        return -errno;
 
-               iov[0].iov_len -= ret;
-               iov[0].iov_base += ret;
+               iov.iov_len -= ret;
+               iov.iov_base += ret;
 
                while (ret) {
                        ret2 = splice(sd->pipe[0], NULL, f->fd, &off, ret, 0);
@@ -106,13 +159,36 @@ static int fio_splice_write(struct thread_data *td, struct io_u *io_u)
        return io_u->xfer_buflen;
 }
 
+static void splice_unmap_io_u(struct thread_data *td, struct io_u *io_u)
+{
+       struct spliceio_data *sd = td->io_ops->data;
+       struct iovec iov = {
+               .iov_base = io_u->xfer_buf,
+               .iov_len = io_u->xfer_buflen,
+       };
+
+       vmsplice(sd->pipe[0], &iov, 1, SPLICE_F_UNMAP);
+}
+
 static int fio_spliceio_queue(struct thread_data *td, struct io_u *io_u)
 {
+       struct spliceio_data *sd = td->io_ops->data;
        int ret;
 
-       if (io_u->ddir == DDIR_READ)
-               ret = fio_splice_read(td, io_u);
-       else if (io_u->ddir == DDIR_WRITE)
+       if (io_u->ddir == DDIR_READ) {
+               if (sd->vmsplice_to_user) {
+                       ret = fio_splice_read(td, io_u);
+                       /*
+                        * This kernel doesn't support vmsplice to user
+                        * space. Reset the vmsplice_to_user flag, so that
+                        * we retry below and don't hit this path again.
+                        */
+                       if (ret == -EBADF)
+                               sd->vmsplice_to_user = 0;
+               }
+               if (!sd->vmsplice_to_user)
+                       ret = fio_splice_read_old(td, io_u);
+       } else if (io_u->ddir == DDIR_WRITE)
                ret = fio_splice_write(td, io_u);
        else
                ret = fsync(io_u->file->fd);
@@ -154,6 +230,11 @@ static int fio_spliceio_init(struct thread_data *td)
                return 1;
        }
 
+       /*
+        * Assume this work, we'll reset this if it doesn't
+        */
+       sd->vmsplice_to_user = 1;
+
        td->io_ops->data = sd;
        return 0;
 }