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From bb1f691dc410ce11ac9675ced70e78a3ce2511b0 Mon Sep 17 00:00:00 2001
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Date: Mon, 27 Jan 2020 19:01:03 +0100
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Subject: [PATCH 032/116] virtiofsd: Send replies to messages
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Message-id: <20200127190227.40942-29-dgilbert@redhat.com>
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Patchwork-id: 93485
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O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 028/112] virtiofsd: Send replies to messages
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Bugzilla: 1694164
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Route fuse out messages back through the same queue elements
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that had the command that triggered the request.
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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(cherry picked from commit df57ba919ec3edef9cc208d35685095e6e92713e)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 tools/virtiofsd/fuse_lowlevel.c |   4 ++
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 tools/virtiofsd/fuse_virtio.c   | 107 ++++++++++++++++++++++++++++++++++++++--
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 tools/virtiofsd/fuse_virtio.h   |   4 ++
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 3 files changed, 111 insertions(+), 4 deletions(-)
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diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c
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index af09fa2..380d93b 100644
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--- a/tools/virtiofsd/fuse_lowlevel.c
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+++ b/tools/virtiofsd/fuse_lowlevel.c
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@@ -171,6 +171,10 @@ static int fuse_send_msg(struct fuse_session *se, struct fuse_chan *ch,
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         }
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     }
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+    if (fuse_lowlevel_is_virtio(se)) {
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+        return virtio_send_msg(se, ch, iov, count);
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+    }
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+
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     abort(); /* virtio should have taken it before here */
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     return 0;
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 }
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diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
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index 3841b20..05d0e29 100644
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--- a/tools/virtiofsd/fuse_virtio.c
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+++ b/tools/virtiofsd/fuse_virtio.c
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@@ -41,6 +41,9 @@ struct fv_QueueInfo {
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     /* Our queue index, corresponds to array position */
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     int qidx;
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     int kick_fd;
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+
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+    /* The element for the command currently being processed */
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+    VuVirtqElement *qe;
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 };
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 /*
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@@ -121,6 +124,105 @@ static void copy_from_iov(struct fuse_buf *buf, size_t out_num,
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     }
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 }
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+/*
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+ * Copy from one iov to another, the given number of bytes
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+ * The caller must have checked sizes.
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+ */
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+static void copy_iov(struct iovec *src_iov, int src_count,
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+                     struct iovec *dst_iov, int dst_count, size_t to_copy)
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+{
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+    size_t dst_offset = 0;
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+    /* Outer loop copies 'src' elements */
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+    while (to_copy) {
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+        assert(src_count);
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+        size_t src_len = src_iov[0].iov_len;
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+        size_t src_offset = 0;
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+
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+        if (src_len > to_copy) {
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+            src_len = to_copy;
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+        }
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+        /* Inner loop copies contents of one 'src' to maybe multiple dst. */
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+        while (src_len) {
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+            assert(dst_count);
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+            size_t dst_len = dst_iov[0].iov_len - dst_offset;
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+            if (dst_len > src_len) {
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+                dst_len = src_len;
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+            }
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+
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+            memcpy(dst_iov[0].iov_base + dst_offset,
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+                   src_iov[0].iov_base + src_offset, dst_len);
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+            src_len -= dst_len;
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+            to_copy -= dst_len;
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+            src_offset += dst_len;
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+            dst_offset += dst_len;
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+
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+            assert(dst_offset <= dst_iov[0].iov_len);
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+            if (dst_offset == dst_iov[0].iov_len) {
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+                dst_offset = 0;
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+                dst_iov++;
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+                dst_count--;
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+            }
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+        }
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+        src_iov++;
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+        src_count--;
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+    }
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+}
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+
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+/*
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+ * Called back by ll whenever it wants to send a reply/message back
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+ * The 1st element of the iov starts with the fuse_out_header
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+ * 'unique'==0 means it's a notify message.
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+ */
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+int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,
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+                    struct iovec *iov, int count)
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+{
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+    VuVirtqElement *elem;
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+    VuVirtq *q;
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+
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+    assert(count >= 1);
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+    assert(iov[0].iov_len >= sizeof(struct fuse_out_header));
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+
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+    struct fuse_out_header *out = iov[0].iov_base;
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+    /* TODO: Endianness! */
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+
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+    size_t tosend_len = iov_size(iov, count);
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+
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+    /* unique == 0 is notification, which we don't support */
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+    assert(out->unique);
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+    /* For virtio we always have ch */
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+    assert(ch);
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+    elem = ch->qi->qe;
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+    q = &ch->qi->virtio_dev->dev.vq[ch->qi->qidx];
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+
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+    /* The 'in' part of the elem is to qemu */
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+    unsigned int in_num = elem->in_num;
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+    struct iovec *in_sg = elem->in_sg;
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+    size_t in_len = iov_size(in_sg, in_num);
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+    fuse_log(FUSE_LOG_DEBUG, "%s: elem %d: with %d in desc of length %zd\n",
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+             __func__, elem->index, in_num, in_len);
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+
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+    /*
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+     * The elem should have room for a 'fuse_out_header' (out from fuse)
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+     * plus the data based on the len in the header.
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+     */
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+    if (in_len < sizeof(struct fuse_out_header)) {
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+        fuse_log(FUSE_LOG_ERR, "%s: elem %d too short for out_header\n",
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+                 __func__, elem->index);
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+        return -E2BIG;
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+    }
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+    if (in_len < tosend_len) {
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+        fuse_log(FUSE_LOG_ERR, "%s: elem %d too small for data len %zd\n",
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+                 __func__, elem->index, tosend_len);
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+        return -E2BIG;
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+    }
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+
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+    copy_iov(iov, count, in_sg, in_num, tosend_len);
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+    vu_queue_push(&se->virtio_dev->dev, q, elem, tosend_len);
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+    vu_queue_notify(&se->virtio_dev->dev, q);
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+
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+    return 0;
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+}
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+
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 /* Thread function for individual queues, created when a queue is 'started' */
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 static void *fv_queue_thread(void *opaque)
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 {
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@@ -226,13 +328,10 @@ static void *fv_queue_thread(void *opaque)
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             /* TODO! Endianness of header */
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-            /* TODO: Fixup fuse_send_msg */
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             /* TODO: Add checks for fuse_session_exited */
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             fuse_session_process_buf_int(se, &fbuf, &ch);
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-            /* TODO: vu_queue_push(dev, q, elem, qi->write_count); */
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-            vu_queue_notify(dev, q);
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-
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+            qi->qe = NULL;
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             free(elem);
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             elem = NULL;
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         }
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diff --git a/tools/virtiofsd/fuse_virtio.h b/tools/virtiofsd/fuse_virtio.h
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index 23026d6..135a148 100644
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--- a/tools/virtiofsd/fuse_virtio.h
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+++ b/tools/virtiofsd/fuse_virtio.h
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@@ -22,4 +22,8 @@ int virtio_session_mount(struct fuse_session *se);
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 int virtio_loop(struct fuse_session *se);
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+
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+int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,
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+                    struct iovec *iov, int count);
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+
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 #endif
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-- 
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1.8.3.1
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