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Blame SOURCES/kvm-virtiofsd-Pass-write-iov-s-all-the-way-through.patch

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From d5986c804f05070a07dfe702f7c66357daaa1ab6 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 19:01:20 +0100
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Subject: [PATCH 049/116] virtiofsd: Pass write iov's all the way through
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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: <20200127190227.40942-46-dgilbert@redhat.com>
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Patchwork-id: 93497
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O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 045/112] virtiofsd: Pass write iov's all the way through
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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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Pass the write iov pointing to guest RAM all the way through rather
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than copying the data.
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Reviewed-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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(cherry picked from commit e17f7a580e2c599330ad3a6946be615ca2fe97d9)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 tools/virtiofsd/fuse_virtio.c | 79 +++++++++++++++++++++++++++++++++++++++----
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 1 file changed, 73 insertions(+), 6 deletions(-)
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diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
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index fd588a4..872968f 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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@@ -454,6 +454,10 @@ static void *fv_queue_thread(void *opaque)
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                  __func__, qi->qidx, (size_t)evalue, in_bytes, out_bytes);
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         while (1) {
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+            bool allocated_bufv = false;
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+            struct fuse_bufvec bufv;
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+            struct fuse_bufvec *pbufv;
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+
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             /*
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              * An element contains one request and the space to send our
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              * response They're spread over multiple descriptors in a
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@@ -495,14 +499,76 @@ static void *fv_queue_thread(void *opaque)
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                          __func__, elem->index);
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                 assert(0); /* TODO */
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             }
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-            copy_from_iov(&fbuf, out_num, out_sg);
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-            fbuf.size = out_len;
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+            /* Copy just the first element and look at it */
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+            copy_from_iov(&fbuf, 1, out_sg);
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+
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+            if (out_num > 2 &&
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+                out_sg[0].iov_len == sizeof(struct fuse_in_header) &&
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+                ((struct fuse_in_header *)fbuf.mem)->opcode == FUSE_WRITE &&
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+                out_sg[1].iov_len == sizeof(struct fuse_write_in)) {
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+                /*
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+                 * For a write we don't actually need to copy the
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+                 * data, we can just do it straight out of guest memory
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+                 * but we must still copy the headers in case the guest
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+                 * was nasty and changed them while we were using them.
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+                 */
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+                fuse_log(FUSE_LOG_DEBUG, "%s: Write special case\n", __func__);
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+
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+                /* copy the fuse_write_in header after the fuse_in_header */
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+                fbuf.mem += out_sg->iov_len;
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+                copy_from_iov(&fbuf, 1, out_sg + 1);
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+                fbuf.mem -= out_sg->iov_len;
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+                fbuf.size = out_sg[0].iov_len + out_sg[1].iov_len;
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+
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+                /* Allocate the bufv, with space for the rest of the iov */
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+                allocated_bufv = true;
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+                pbufv = malloc(sizeof(struct fuse_bufvec) +
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+                               sizeof(struct fuse_buf) * (out_num - 2));
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+                if (!pbufv) {
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+                    vu_queue_unpop(dev, q, elem, 0);
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+                    free(elem);
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+                    fuse_log(FUSE_LOG_ERR, "%s: pbufv malloc failed\n",
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+                             __func__);
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+                    goto out;
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+                }
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+
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+                pbufv->count = 1;
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+                pbufv->buf[0] = fbuf;
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+
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+                size_t iovindex, pbufvindex;
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+                iovindex = 2; /* 2 headers, separate iovs */
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+                pbufvindex = 1; /* 2 headers, 1 fusebuf */
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+
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+                for (; iovindex < out_num; iovindex++, pbufvindex++) {
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+                    pbufv->count++;
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+                    pbufv->buf[pbufvindex].pos = ~0; /* Dummy */
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+                    pbufv->buf[pbufvindex].flags = 0;
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+                    pbufv->buf[pbufvindex].mem = out_sg[iovindex].iov_base;
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+                    pbufv->buf[pbufvindex].size = out_sg[iovindex].iov_len;
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+                }
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+            } else {
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+                /* Normal (non fast write) path */
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+
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+                /* Copy the rest of the buffer */
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+                fbuf.mem += out_sg->iov_len;
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+                copy_from_iov(&fbuf, out_num - 1, out_sg + 1);
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+                fbuf.mem -= out_sg->iov_len;
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+                fbuf.size = out_len;
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-            /* TODO! Endianness of header */
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+                /* TODO! Endianness of header */
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-            /* TODO: Add checks for fuse_session_exited */
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-            struct fuse_bufvec bufv = { .buf[0] = fbuf, .count = 1 };
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-            fuse_session_process_buf_int(se, &bufv, &ch);
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+                /* TODO: Add checks for fuse_session_exited */
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+                bufv.buf[0] = fbuf;
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+                bufv.count = 1;
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+                pbufv = &buf;;
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+            }
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+            pbufv->idx = 0;
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+            pbufv->off = 0;
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+            fuse_session_process_buf_int(se, pbufv, &ch);
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+
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+            if (allocated_bufv) {
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+                free(pbufv);
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+            }
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             if (!qi->reply_sent) {
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                 fuse_log(FUSE_LOG_DEBUG, "%s: elem %d no reply sent\n",
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@@ -516,6 +582,7 @@ static void *fv_queue_thread(void *opaque)
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             elem = NULL;
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         }
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     }
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+out:
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     pthread_mutex_destroy(&ch.lock);
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     free(fbuf.mem);
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-- 
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1.8.3.1
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