splice: fix problem with current mainline kernels

splice was updated to work well with the newer vmsplice patches,
where we don't have to copy data at all. But that broke the
regular vmsplice that copies data, which is all the mainline kernel
still support.

Fix that up, so we do appropriate fallbacks. Fixes the problem
reported by gurudas pai <gurudas.pai@oracle.com>

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/engines/splice.c b/engines/splice.c
index 2344fddd3be30b2192f4ea1e4d1b921a8baebd70..868f6e0d3b6977ee3b9b0dea52ba3c52045c90b8 100644 (file)
--- a/engines/splice.c
+++ b/engines/splice.c
@@ -20,6 +20,7 @@
 struct spliceio_data {
        int pipe[2];
        int vmsplice_to_user;
+       int vmsplice_to_user_map;
 };
 
 /*
@@ -76,20 +77,28 @@ 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 = 0 , buflen, mmap_len;
+       int ret , buflen, mmap_len;
        off_t offset;
        void *p, *map;
 
+restart:
+       ret = 0;
        offset = io_u->offset;
        mmap_len = buflen = io_u->xfer_buflen;
 
-       map = mmap(io_u->xfer_buf, buflen, PROT_READ, MAP_PRIVATE|OS_MAP_ANON, 0, 0);
-       if (map == MAP_FAILED) {
-               td_verror(td, errno, "mmap io_u");
-               return -1;
+       if (sd->vmsplice_to_user_map) {
+               map = mmap(io_u->xfer_buf, buflen, PROT_READ, MAP_PRIVATE|OS_MAP_ANON, 0, 0);
+               if (map == MAP_FAILED) {
+                       td_verror(td, errno, "mmap io_u");
+                       return -1;
+               }
+
+               p = map;
+       } else {
+               map = NULL;
+               p = io_u->xfer_buf;
        }
 
-       p = map;
        while (buflen) {
                int this_len = buflen;
                int flags = 0;
@@ -116,6 +125,11 @@ static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
                while (iov.iov_len) {
                        ret = vmsplice(sd->pipe[0], &iov, 1, SPLICE_F_MOVE);
                        if (ret < 0) {
+                               if (errno == EFAULT && sd->vmsplice_to_user_map) {
+                                       sd->vmsplice_to_user_map = 0;
+                                       munmap(map, mmap_len);
+                                       goto restart;
+                               }
                                td_verror(td, errno, "vmsplice");
                                break;
                        } else if (!ret) {
@@ -131,7 +145,7 @@ static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
                        break;
        }
 
-       if (munmap(map, mmap_len) < 0) {
+       if (sd->vmsplice_to_user_map && munmap(map, mmap_len) < 0) {
                td_verror(td, errno, "munnap io_u");
                return -1;
        }
@@ -247,6 +261,12 @@ static int fio_spliceio_init(struct thread_data *td)
         */
        sd->vmsplice_to_user = 1;
 
+       /*
+        * Works with "real" vmsplice to user, eg mapping pages directly.
+        * Reset if we fail.
+        */
+       sd->vmsplice_to_user_map = 1;
+
        /*
         * And if vmsplice_to_user works, we definitely need aligned
         * buffers. Just set ->odirect to force that.