[Xen-devel] [PATCH 09/27] libxl: provide libxl__datacopier_*

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

General facility for ao operations to shovel data between fds.

This will be used by the bootloader machinery.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Changes in v7:
 * assert that the ao is non-null on _init.
---
 tools/libxl/Makefile         |    3 +-
 tools/libxl/libxl_aoutils.c  |  189 ++++++++++++++++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h |   40 +++++++++
 3 files changed, 231 insertions(+), 1 deletions(-)
 create mode 100644 tools/libxl/libxl_aoutils.c

diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
index 1261d43..5d9227e 100644
--- a/tools/libxl/Makefile
+++ b/tools/libxl/Makefile
@@ -64,7 +64,8 @@ LIBXL_LIBS += -lyajl
 
 LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
                        libxl_dom.o libxl_exec.o libxl_xshelp.o libxl_device.o \
-                       libxl_internal.o libxl_utils.o libxl_uuid.o 
libxl_json.o \
+                       libxl_internal.o libxl_utils.o libxl_uuid.o \
+                       libxl_json.o libxl_aoutils.o \
                        libxl_qmp.o libxl_event.o libxl_fork.o $(LIBXL_OBJS-y)
 LIBXL_OBJS += _libxl_types.o libxl_flask.o _libxl_types_internal.o
 
diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
new file mode 100644
index 0000000..4c60ad9
--- /dev/null
+++ b/tools/libxl/libxl_aoutils.c
@@ -0,0 +1,189 @@
+/*
+ * Copyright (C) 2010      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include "libxl_osdeps.h" /* must come before any other headers */
+
+#include "libxl_internal.h"
+
+/*----- data copier -----*/
+
+void libxl__datacopier_init(libxl__datacopier_state *dc)
+{
+    assert(dc->ao);
+    libxl__ev_fd_init(&dc->toread);
+    libxl__ev_fd_init(&dc->towrite);
+    LIBXL_TAILQ_INIT(&dc->bufs);
+}
+
+void libxl__datacopier_kill(libxl__datacopier_state *dc)
+{
+    STATE_AO_GC(dc->ao);
+    libxl__datacopier_buf *buf, *tbuf;
+
+    libxl__ev_fd_deregister(gc, &dc->toread);
+    libxl__ev_fd_deregister(gc, &dc->towrite);
+    LIBXL_TAILQ_FOREACH_SAFE(buf, &dc->bufs, entry, tbuf)
+        free(buf);
+    LIBXL_TAILQ_INIT(&dc->bufs);
+}
+
+static void datacopier_callback(libxl__egc *egc, libxl__datacopier_state *dc,
+                                int onwrite, int errnoval)
+{
+    libxl__datacopier_kill(dc);
+    dc->callback(egc, dc, onwrite, errnoval);
+}
+
+static void datacopier_writable(libxl__egc *egc, libxl__ev_fd *ev,
+                                int fd, short events, short revents);
+
+static void datacopier_check_state(libxl__egc *egc, libxl__datacopier_state 
*dc)
+{
+    STATE_AO_GC(dc->ao);
+    int rc;
+    
+    if (dc->used) {
+        if (!libxl__ev_fd_isregistered(&dc->towrite)) {
+            rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
+                                       dc->writefd, POLLOUT);
+            if (rc) {
+                LOG(ERROR, "unable to establish write event on %s"
+                    " during copy of %s", dc->writewhat, dc->copywhat);
+                datacopier_callback(egc, dc, -1, 0);
+                return;
+            }
+        }
+    } else if (!libxl__ev_fd_isregistered(&dc->toread)) {
+        /* we have had eof */
+        datacopier_callback(egc, dc, 0, 0);
+        return;
+    } else {
+        /* nothing buffered, but still reading */
+        libxl__ev_fd_deregister(gc, &dc->towrite);
+    }
+}
+
+static void datacopier_readable(libxl__egc *egc, libxl__ev_fd *ev,
+                                int fd, short events, short revents) {
+    libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, toread);
+    STATE_AO_GC(dc->ao);
+
+    if (revents & ~POLLIN) {
+        LOG(ERROR, "unexpected poll event 0x%x (should be POLLIN)"
+            " on %s during copy of %s", revents, dc->readwhat, dc->copywhat);
+        datacopier_callback(egc, dc, -1, 0);
+        return;
+    }
+    assert(revents & POLLIN);
+    for (;;) {
+        while (dc->used >= dc->maxsz) {
+            libxl__datacopier_buf *rm = LIBXL_TAILQ_FIRST(&dc->bufs);
+            dc->used -= rm->used;
+            assert(dc->used >= 0);
+            LIBXL_TAILQ_REMOVE(&dc->bufs, rm, entry);
+            free(rm);
+        }
+
+        libxl__datacopier_buf *buf =
+            LIBXL_TAILQ_LAST(&dc->bufs, libxl__datacopier_bufs);
+        if (!buf || buf->used >= sizeof(buf->buf)) {
+            buf = malloc(sizeof(*buf));
+            if (!buf) libxl__alloc_failed(CTX, __func__, 1, sizeof(*buf));
+            buf->used = 0;
+            LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
+        }
+        int r = read(ev->fd,
+                     buf->buf + buf->used,
+                     sizeof(buf->buf) - buf->used);
+        if (r < 0) {
+            if (errno == EINTR) continue;
+            if (errno == EWOULDBLOCK) break;
+            LOGE(ERROR, "error reading %s during copy of %s",
+                 dc->readwhat, dc->copywhat);
+            datacopier_callback(egc, dc, 0, errno);
+            return;
+        }
+        if (r == 0) {
+            libxl__ev_fd_deregister(gc, &dc->toread);
+            break;
+        }
+        buf->used += r;
+        dc->used += r;
+        assert(buf->used <= sizeof(buf->buf));
+    }
+    datacopier_check_state(egc, dc);
+}
+
+static void datacopier_writable(libxl__egc *egc, libxl__ev_fd *ev,
+                                int fd, short events, short revents) {
+    libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, towrite);
+    STATE_AO_GC(dc->ao);
+
+    if (revents & ~POLLOUT) {
+        LOG(ERROR, "unexpected poll event 0x%x (should be POLLOUT)"
+            " on %s during copy of %s", revents, dc->writewhat, dc->copywhat);
+        datacopier_callback(egc, dc, -1, 0);
+        return;
+    }
+    assert(revents & POLLOUT);
+    for (;;) {
+        libxl__datacopier_buf *buf = LIBXL_TAILQ_FIRST(&dc->bufs);
+        if (!buf)
+            break;
+        if (!buf->used) {
+            LIBXL_TAILQ_REMOVE(&dc->bufs, buf, entry);
+            free(buf);
+            continue;
+        }
+        int r = write(ev->fd, buf->buf, buf->used);
+        if (r < 0) {
+            if (errno == EINTR) continue;
+            if (errno == EWOULDBLOCK) break;
+            LOGE(ERROR, "error writing to %s during copy of %s",
+                 dc->writewhat, dc->copywhat);
+            datacopier_callback(egc, dc, 1, errno);
+            return;
+        }
+        assert(r > 0);
+        assert(r <= buf->used);
+        buf->used -= r;
+        dc->used -= r;
+        assert(dc->used >= 0);
+        memmove(buf->buf, buf->buf+r, buf->used);
+    }
+    datacopier_check_state(egc, dc);
+}
+
+int libxl__datacopier_start(libxl__datacopier_state *dc)
+{
+    int rc;
+    STATE_AO_GC(dc->ao);
+
+    libxl__datacopier_init(dc);
+
+    rc = libxl__ev_fd_register(gc, &dc->toread, datacopier_readable,
+                               dc->readfd, POLLIN);
+    if (rc) goto out;
+
+    rc = libxl__ev_fd_register(gc, &dc->towrite, datacopier_writable,
+                               dc->writefd, POLLOUT);
+    if (rc) goto out;
+
+    return 0;
+
+ out:
+    libxl__datacopier_kill(dc);
+    return rc;
+}
+
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index e25569c..be11fbd 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -840,6 +840,7 @@ _hidden int libxl__ev_devstate_wait(libxl__gc *gc, 
libxl__ev_devstate *ds,
  */
 _hidden int libxl__try_phy_backend(mode_t st_mode);
 
+
 /* from libxl_pci */
 
 _hidden int libxl__device_pci_add(libxl__gc *gc, uint32_t domid, 
libxl_device_pci *pcidev, int starting);
@@ -1473,6 +1474,45 @@ _hidden const char *libxl__xen_script_dir_path(void);
 _hidden const char *libxl__lock_dir_path(void);
 _hidden const char *libxl__run_dir_path(void);
 
+/*----- datacopier: copies data from one fd to another -----*/
+
+typedef struct libxl__datacopier_state libxl__datacopier_state;
+typedef struct libxl__datacopier_buf libxl__datacopier_buf;
+
+/* onwrite==1 means failure happened when writing, logged, errnoval is valid
+ * onwrite==0 means failure happened when reading
+ *     errnoval==0 means we got eof and all data was written
+ *     errnoval!=0 means we had a read error, logged
+ * onwrite==-1 means some other internal failure, errnoval not valid, logged
+ * in all cases copier is killed before calling this callback */
+typedef void libxl__datacopier_callback(libxl__egc *egc,
+     libxl__datacopier_state *dc, int onwrite, int errnoval);
+
+struct libxl__datacopier_buf {
+    /* private to datacopier */
+    LIBXL_TAILQ_ENTRY(libxl__datacopier_buf) entry;
+    int used;
+    char buf[1000];
+};
+
+struct libxl__datacopier_state {
+    /* caller must fill these in, and they must all remain valid */
+    libxl__ao *ao;
+    int readfd, writefd;
+    ssize_t maxsz;
+    const char *copywhat, *readwhat, *writewhat; /* for error msgs */
+    libxl__datacopier_callback *callback;
+    /* remaining fields are private to datacopier */
+    libxl__ev_fd toread, towrite;
+    ssize_t used;
+    LIBXL_TAILQ_HEAD(libxl__datacopier_bufs, libxl__datacopier_buf) bufs;
+};
+
+_hidden void libxl__datacopier_init(libxl__datacopier_state *dc);
+_hidden void libxl__datacopier_kill(libxl__datacopier_state *dc);
+_hidden int libxl__datacopier_start(libxl__datacopier_state *dc);
+
+
 /*
  * Convenience macros.
  */
-- 
1.7.2.5


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