[Virtio-fs] [PATCH v2 1/2][RFC] virtiofsd: virtiofsd: add definition of fuse_buf_writev()

[piaojun]

Define fuse_buf_writev() which use pwritev and writev to improve io
bandwidth.

Signed-off-by: Jun Piao <piaojun at huawei.com>
Suggested-by: Dr. David Alan Gilbert <dgilbert at redhat.com>
---
 contrib/virtiofsd/buffer.c      | 37 +++++++++++++++++++++++++++++++++++++
 contrib/virtiofsd/fuse_common.h | 14 ++++++++++++++
 contrib/virtiofsd/seccomp.c     |  2 ++
 3 files changed, 53 insertions(+)

diff --git a/contrib/virtiofsd/buffer.c b/contrib/virtiofsd/buffer.c
index 655be137..642830f 100644
--- a/contrib/virtiofsd/buffer.c
+++ b/contrib/virtiofsd/buffer.c
@@ -15,6 +15,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <assert.h>
+#include <stdlib.h>

 size_t fuse_buf_size(const struct fuse_bufvec *bufv)
 {
@@ -71,6 +72,42 @@ static ssize_t fuse_buf_write(const struct fuse_buf *dst, size_t dst_off,
 	return copied;
 }

+ssize_t fuse_buf_writev(fuse_req_t req,
+			     struct fuse_bufvec *out_buf,
+			     struct fuse_bufvec *in_buf,
+			     enum fuse_buf_copy_flags flags)
+{
+	ssize_t res, i, buf_index, iovcnt;
+	struct iovec * iov;
+	int fd = out_buf->buf[0].fd;
+	off_t pos = out_buf->buf[0].pos;
+
+	if (in_buf->count > 2)
+		iovcnt = in_buf->count - 1;
+	else
+		iovcnt = 1;
+
+	iov = malloc(iovcnt * sizeof(struct iovec));
+	if (!iov)
+		return -ENOMEM;
+
+	for (i = 0, buf_index = 1; i < iovcnt; i++, buf_index++) {
+		iov[i].iov_base = in_buf->buf[buf_index].mem;
+		iov[i].iov_len = in_buf->buf[buf_index].size;
+	}
+
+	if (flags & FUSE_BUF_FD_SEEK)
+		res = pwritev(fd, iov, iovcnt, pos);
+	else
+		res = writev(fd, iov, iovcnt);
+
+	if (res == -1 || res == 0)
+		res = -errno;
+
+	free(iov);
+	return res;
+}
+
 static ssize_t fuse_buf_read(const struct fuse_buf *dst, size_t dst_off,
 			     const struct fuse_buf *src, size_t src_off,
 			     size_t len)
diff --git a/contrib/virtiofsd/fuse_common.h b/contrib/virtiofsd/fuse_common.h
index 001e6d6..7c07da7 100644
--- a/contrib/virtiofsd/fuse_common.h
+++ b/contrib/virtiofsd/fuse_common.h
@@ -730,6 +730,20 @@ ssize_t fuse_buf_copy(fuse_req_t req,
 		      enum fuse_buf_copy_flags flags);

 /**
+ * Write data from one buffer vector to another
+ *
+ * @param req The request this copy is part of
+ * @param out_buf destination buffer vector
+ * @param in_buf source buffer vector
+ * @param flags flags controlling the copy
+ * @return actual number of bytes written or -errno on error
+ */
+ssize_t fuse_buf_writev(fuse_req_t req,
+		      struct fuse_bufvec *out_buf,
+		      struct fuse_bufvec *in_buf,
+		      enum fuse_buf_copy_flags flags);
+
+/**
  * Memory buffer iterator
  *
  */
diff --git a/contrib/virtiofsd/seccomp.c b/contrib/virtiofsd/seccomp.c
index 5f1c873..4bba30b 100644
--- a/contrib/virtiofsd/seccomp.c
+++ b/contrib/virtiofsd/seccomp.c
@@ -60,6 +60,7 @@ static const int syscall_whitelist[] = {
 	SCMP_SYS(ppoll),
 	SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */
 	SCMP_SYS(preadv),
+	SCMP_SYS(pwritev),
 	SCMP_SYS(pwrite64),
 	SCMP_SYS(read),
 	SCMP_SYS(readlinkat),
@@ -78,6 +79,7 @@ static const int syscall_whitelist[] = {
 	SCMP_SYS(unlinkat),
 	SCMP_SYS(utimensat),
 	SCMP_SYS(write),
+	SCMP_SYS(writev),
 };

 /* Syscalls used when --syslog is enabled */
--