From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Date: Mon, 27 Jan 2020 19:01:19 +0000

Subject: [PATCH] virtiofsd: Plumb fuse_bufvec through to do_write_buf

Let fuse_session_process_buf_int take a fuse_bufvec * instead of a

fuse_buf;  and then through to do_write_buf - where in the best

case it can pass that straight through to op.write_buf without copying

(other than skipping a header).

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit 469f9d2fc405b0508e6cf1b4b5bbcadfc82064e5)

---

 tools/virtiofsd/fuse_i.h        |  2 +-

 tools/virtiofsd/fuse_lowlevel.c | 61 ++++++++++++++++++++++-----------

 tools/virtiofsd/fuse_virtio.c   |  3 +-

 3 files changed, 44 insertions(+), 22 deletions(-)

diff --git a/tools/virtiofsd/fuse_i.h b/tools/virtiofsd/fuse_i.h

index 45995f3246..a20854f1c4 100644

--- a/tools/virtiofsd/fuse_i.h

+++ b/tools/virtiofsd/fuse_i.h

@@ -100,7 +100,7 @@ int fuse_send_reply_iov_nofree(fuse_req_t req, int error, struct iovec *iov,

 void fuse_free_req(fuse_req_t req);

 void fuse_session_process_buf_int(struct fuse_session *se,

-                                  const struct fuse_buf *buf,

+                                  struct fuse_bufvec *bufv,

                                   struct fuse_chan *ch);

diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c

index 95f4db8fcf..7e10995adc 100644

--- a/tools/virtiofsd/fuse_lowlevel.c

+++ b/tools/virtiofsd/fuse_lowlevel.c

@@ -1004,11 +1004,12 @@ static void do_write(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)

 }

 static void do_write_buf(fuse_req_t req, fuse_ino_t nodeid, const void *inarg,

-                         const struct fuse_buf *ibuf)

+                         struct fuse_bufvec *ibufv)

 {

     struct fuse_session *se = req->se;

-    struct fuse_bufvec bufv = {

-        .buf[0] = *ibuf,

+    struct fuse_bufvec *pbufv = ibufv;

+    struct fuse_bufvec tmpbufv = {

+        .buf[0] = ibufv->buf[0],

         .count = 1,

     };

     struct fuse_write_in *arg = (struct fuse_write_in *)inarg;

@@ -1018,22 +1019,31 @@ static void do_write_buf(fuse_req_t req, fuse_ino_t nodeid, const void *inarg,

     fi.fh = arg->fh;

     fi.writepage = arg->write_flags & FUSE_WRITE_CACHE;

-    fi.lock_owner = arg->lock_owner;

-    fi.flags = arg->flags;

-    if (!(bufv.buf[0].flags & FUSE_BUF_IS_FD)) {

-        bufv.buf[0].mem = PARAM(arg);

-    }

-

-    bufv.buf[0].size -=

-        sizeof(struct fuse_in_header) + sizeof(struct fuse_write_in);

-    if (bufv.buf[0].size < arg->size) {

-        fuse_log(FUSE_LOG_ERR, "fuse: do_write_buf: buffer size too small\n");

-        fuse_reply_err(req, EIO);

-        return;

+    if (ibufv->count == 1) {

+        fi.lock_owner = arg->lock_owner;

+        fi.flags = arg->flags;

+        if (!(tmpbufv.buf[0].flags & FUSE_BUF_IS_FD)) {

+            tmpbufv.buf[0].mem = PARAM(arg);

+        }

+        tmpbufv.buf[0].size -=

+            sizeof(struct fuse_in_header) + sizeof(struct fuse_write_in);

+        if (tmpbufv.buf[0].size < arg->size) {

+            fuse_log(FUSE_LOG_ERR,

+                     "fuse: do_write_buf: buffer size too small\n");

+            fuse_reply_err(req, EIO);

+            return;

+        }

+        tmpbufv.buf[0].size = arg->size;

+        pbufv = &tmpbufv;

+    } else {

+        /*

+         *  Input bufv contains the headers in the first element

+         * and the data in the rest, we need to skip that first element

+         */

+        ibufv->buf[0].size = 0;

     }

-    bufv.buf[0].size = arg->size;

-    se->op.write_buf(req, nodeid, &bufv, arg->offset, &fi);

+    se->op.write_buf(req, nodeid, pbufv, arg->offset, &fi);

 }

 static void do_flush(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)

@@ -2024,13 +2034,24 @@ static const char *opname(enum fuse_opcode opcode)

 void fuse_session_process_buf(struct fuse_session *se,

                               const struct fuse_buf *buf)

 {

-    fuse_session_process_buf_int(se, buf, NULL);

+    struct fuse_bufvec bufv = { .buf[0] = *buf, .count = 1 };

+    fuse_session_process_buf_int(se, &bufv, NULL);

 }

+/*

+ * Restriction:

+ *   bufv is normally a single entry buffer, except for a write

+ *   where (if it's in memory) then the bufv may be multiple entries,

+ *   where the first entry contains all headers and subsequent entries

+ *   contain data

+ *   bufv shall not use any offsets etc to make the data anything

+ *   other than contiguous starting from 0.

+ */

 void fuse_session_process_buf_int(struct fuse_session *se,

-                                  const struct fuse_buf *buf,

+                                  struct fuse_bufvec *bufv,

                                   struct fuse_chan *ch)

 {

+    const struct fuse_buf *buf = bufv->buf;

     struct fuse_in_header *in;

     const void *inarg;

     struct fuse_req *req;

@@ -2108,7 +2129,7 @@ void fuse_session_process_buf_int(struct fuse_session *se,

     inarg = (void *)&in[1];

     if (in->opcode == FUSE_WRITE && se->op.write_buf) {

-        do_write_buf(req, in->nodeid, inarg, buf);

+        do_write_buf(req, in->nodeid, inarg, bufv);

     } else {

         fuse_ll_ops[in->opcode].func(req, in->nodeid, inarg);

     }

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c

index 635f87756a..fd588a4829 100644

--- a/tools/virtiofsd/fuse_virtio.c

+++ b/tools/virtiofsd/fuse_virtio.c

@@ -501,7 +501,8 @@ static void *fv_queue_thread(void *opaque)

             /* TODO! Endianness of header */

             /* TODO: Add checks for fuse_session_exited */

-            fuse_session_process_buf_int(se, &fbuf, &ch);

+            struct fuse_bufvec bufv = { .buf[0] = fbuf, .count = 1 };

+            fuse_session_process_buf_int(se, &bufv, &ch);

             if (!qi->reply_sent) {

                 fuse_log(FUSE_LOG_DEBUG, "%s: elem %d no reply sent\n",