[RFC PATCH 3/5] Add a helper to write to a file through the chrooted thread

[Trond Myklebust <trondmy@xxxxxxxxx>]

Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
 support/include/misc.h   |  2 ++
 support/misc/workqueue.c | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/support/include/misc.h b/support/include/misc.h
index 40fb9a37621a..0632df101bbb 100644
--- a/support/include/misc.h
+++ b/support/include/misc.h
@@ -28,6 +28,8 @@ void xthread_work_run_sync(struct xthread_workqueue *wq,
 		void (*fn)(void *), void *data);
 void xthread_workqueue_chroot(struct xthread_workqueue *wq,
 		const char *path);
+ssize_t xthread_write(struct xthread_workqueue *wq,
+		int fd, const char *buf, size_t len);
 
 /* size of the file pointer buffers for rpc procfs files */
 #define RPC_CHAN_BUF_SIZE 32768
diff --git a/support/misc/workqueue.c b/support/misc/workqueue.c
index 16e95e1f6c86..7af76a84e8dd 100644
--- a/support/misc/workqueue.c
+++ b/support/misc/workqueue.c
@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>
 
@@ -197,6 +198,39 @@ void xthread_workqueue_chroot(struct xthread_workqueue *wq,
 	xthread_work_run_sync(wq, xthread_workqueue_do_chroot, (void *)path);
 }
 
+struct xthread_io_data {
+	int fd;
+	const char *buf;
+	size_t len;
+	ssize_t ret;
+	int err;
+};
+
+static void xthread_writefunc(void *data)
+{
+	struct xthread_io_data *d = data;
+
+	d->ret = write(d->fd, d->buf, d->len);
+	if (d->ret < 0)
+		d->err = errno;
+}
+
+ssize_t xthread_write(struct xthread_workqueue *wq,
+		int fd, const char *buf, size_t len)
+{
+	struct xthread_io_data data = {
+		fd,
+		buf,
+		len,
+		0,
+		0
+	};
+	xthread_work_run_sync(wq, xthread_writefunc, &data);
+	if (data.ret < 0)
+		errno = data.err;
+	return data.ret;
+}
+
 #else
 
 struct xthread_workqueue {
@@ -225,4 +259,9 @@ void xthread_workqueue_chroot(struct xthread_workqueue *wq,
 	xlog(L_FATAL, "Unable to run as chroot");
 }
 
+ssize_t xthread_write(struct xthread_workqueue *wq,
+		int fd, const char *buf, size_t len)
+{
+	return write(fd, buf, len);
+}
 #endif /* defined(HAVE_SCHED_H) && defined(HAVE_LIBPTHREAD) && defined(HAVE_UNSHARE) */
-- 
2.21.0