[Qemu-devel] [PATCH] add file: migration support (r2)

[Charles Duffy <Charles_Duffy@messageone.com>]

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This patch adds support for migration to and from file: targets, moves 
common helpers between exec: and file: use cases from migration-exec.c 
to migration.c, and adds a qemu_fdopen() helper parallel to qemu_fopen().

Compared to the previous version submitted, it removes some cruft which 
was accidentally included, and documents the limitations of O_NONBLOCK 
on Linux with local filesystem access.

[-- Attachment #2: qemu-live_migration_file_support-r2.patch --]
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diff --git a/Makefile b/Makefile
index 3ed8b2a..a5db522 100644
--- a/Makefile
+++ b/Makefile
@@ -78,8 +78,8 @@ OBJS+=usb.o usb-hub.o usb-linux.o usb-hid.o usb-msd.o usb-wacom.o
 OBJS+=usb-serial.o usb-net.o
 OBJS+=sd.o ssi-sd.o
 OBJS+=bt.o bt-host.o bt-vhci.o bt-l2cap.o bt-sdp.o bt-hci.o bt-hid.o usb-bt.o
-OBJS+=buffered_file.o migration.o migration-tcp.o net.o qemu-sockets.o
-OBJS+=qemu-char.o aio.o net-checksum.o savevm.o
+OBJS+=buffered_file.o migration.o migration-file.o migration-tcp.o net.o
+OBJS+=qemu-sockets.o qemu-char.o aio.o net-checksum.o savevm.o
 
 ifdef CONFIG_BRLAPI
 OBJS+= baum.o
diff --git a/hw/hw.h b/hw/hw.h
index eab7bb4..4d5ae42 100644
--- a/hw/hw.h
+++ b/hw/hw.h
@@ -35,6 +35,7 @@ QEMUFile *qemu_fopen_ops(void *opaque, QEMUFilePutBufferFunc *put_buffer,
                          QEMUFileRateLimit *rate_limit);
 QEMUFile *qemu_fopen(const char *filename, const char *mode);
 QEMUFile *qemu_fopen_socket(int fd);
+QEMUFile *qemu_fdopen(int fd, const char *mode);
 QEMUFile *qemu_popen(FILE *popen_file, const char *mode);
 QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
 void qemu_fflush(QEMUFile *f);
diff --git a/migration-exec.c b/migration-exec.c
index caeed4b..f625689 100644
--- a/migration-exec.c
+++ b/migration-exec.c
@@ -32,16 +32,6 @@
     do { } while (0)
 #endif
 
-static int file_errno(FdMigrationState *s)
-{
-    return errno;
-}
-
-static int file_write(FdMigrationState *s, const void * buf, size_t size)
-{
-    return write(s->fd, buf, size);
-}
-
 static int exec_close(FdMigrationState *s)
 {
     dprintf("exec_close\n");
@@ -86,8 +76,8 @@ MigrationState *exec_start_outgoing_migration(const char *command,
     s->opaque = qemu_popen(f, "w");
 
     s->close = exec_close;
-    s->get_error = file_errno;
-    s->write = file_write;
+    s->get_error = migrate_file_errno;
+    s->write = migrate_file_write;
     s->mig_state.cancel = migrate_fd_cancel;
     s->mig_state.get_status = migrate_fd_get_status;
     s->mig_state.release = migrate_fd_release;
diff --git a/migration-file.c b/migration-file.c
new file mode 100644
index 0000000..1b90c78
--- /dev/null
+++ b/migration-file.c
@@ -0,0 +1,118 @@
+/*
+ * QEMU live migration
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright Dell MessageOne 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Charles Duffy     <charles_duffy@messageone.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include "qemu_socket.h"
+#include "migration.h"
+#include "qemu-char.h"
+#include "sysemu.h"
+#include "console.h"
+#include "buffered_file.h"
+#include "block.h"
+
+//#define DEBUG_MIGRATION_FILE
+
+#ifdef DEBUG_MIGRATION_FILE
+#define dprintf(fmt, ...) \
+    do { printf("migration-file: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define dprintf(fmt, ...) \
+    do { } while (0)
+#endif
+
+MigrationState *file_start_outgoing_migration(const char *filename,
+                                             int64_t bandwidth_limit,
+                                             int async)
+{
+    FdMigrationState *s;
+
+    s = qemu_mallocz(sizeof(*s));
+    if (s == NULL) {
+        dprintf("Unable to allocate FdMigrationState\n");
+        goto err;
+    }
+
+    /* Note that while O_NONBLOCK is given here, writes to a standard file on
+     * Linux will not return EAGAIN; thus, migration with a sufficiently high
+     * target speed set will effectively pause qemu during migration.
+     * O_NONBLOCK is still used here, such that writes to a named pipe or
+     * similar object may return EAGAIN if appropriate.
+     */
+    s->fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC|O_NONBLOCK, 0666);
+    if (s->fd == -1) {
+        perror("Unable to open migration target");
+        goto err_after_alloc;
+    }
+
+    s->close = migrate_file_close;
+    s->get_error = migrate_file_errno;
+    s->write = migrate_file_write;
+    s->mig_state.cancel = migrate_fd_cancel;
+    s->mig_state.get_status = migrate_fd_get_status;
+    s->mig_state.release = migrate_fd_release;
+
+    s->state = MIG_STATE_ACTIVE;
+    s->detach = !async;
+    s->bandwidth_limit = bandwidth_limit;
+
+    if (s->detach == 1) {
+        dprintf("detaching from monitor\n");
+        monitor_suspend();
+        s->detach = 2;
+    }
+
+    migrate_fd_connect(s);
+    return &s->mig_state;
+
+err_after_alloc:
+    qemu_free(s);
+err:
+    return NULL;
+}
+
+int file_start_incoming_migration(const char *filename)
+{
+    int fd, ret;
+    QEMUFile *f;
+
+    dprintf("Attempting to start an incoming migration\n");
+    fd = open(filename, O_RDONLY);
+    if(fd < 0) {
+        perror("Unable to open migration source");
+        return -errno;
+    }
+    f = qemu_fdopen(fd, "rb");
+    if(f == NULL) {
+        dprintf("unable to wrap file descriptor for incoming migration\n");
+        ret = -errno;
+        close(fd);
+        return ret;
+    }
+    vm_stop(0); /* just in case */
+    ret = qemu_loadvm_state(f);
+    if (ret < 0) {
+        fprintf(stderr, "load of migration failed\n");
+        goto err;
+    }
+    qemu_announce_self();
+    dprintf("successfully loaded vm state\n");
+    vm_start();
+    qemu_fclose(f);
+    return 0;
+
+err:
+    qemu_fclose(f);
+    return -errno;
+}
diff --git a/migration.c b/migration.c
index 0ef777a..709ee49 100644
--- a/migration.c
+++ b/migration.c
@@ -40,6 +40,8 @@ void qemu_start_incoming_migration(const char *uri)
 
     if (strstart(uri, "tcp:", &p))
         tcp_start_incoming_migration(p);
+    else if (strstart(uri, "file:", &p))
+        file_start_incoming_migration(p);
 #if !defined(WIN32)
     else if (strstart(uri, "exec:", &p))
         exec_start_incoming_migration(p);
@@ -55,6 +57,8 @@ void do_migrate(int detach, const char *uri)
 
     if (strstart(uri, "tcp:", &p))
         s = tcp_start_outgoing_migration(p, max_throttle, detach);
+    else if (strstart(uri, "file:", &p))
+        s = file_start_outgoing_migration(p, max_throttle, detach);
 #if !defined(WIN32)
     else if (strstart(uri, "exec:", &p))
         s = exec_start_outgoing_migration(p, max_throttle, detach);
@@ -279,3 +283,18 @@ int migrate_fd_close(void *opaque)
     FdMigrationState *s = opaque;
     return s->close(s);
 }
+
+int migrate_file_errno(FdMigrationState *s)
+{
+    return errno;
+}
+
+int migrate_file_write(FdMigrationState *s, const void * buf, size_t size)
+{
+    return write(s->fd, buf, size);
+}
+
+int migrate_file_close(FdMigrationState *s)
+{
+    return close(s->fd);
+}
diff --git a/migration.h b/migration.h
index 953ec70..dcbda39 100644
--- a/migration.h
+++ b/migration.h
@@ -61,6 +61,12 @@ MigrationState *exec_start_outgoing_migration(const char *host_port,
 					     int64_t bandwidth_limit,
 					     int detach);
 
+int file_start_incoming_migration(const char *filename);
+
+MigrationState *file_start_outgoing_migration(const char *filename,
+                                             int64_t bandwidth_limit,
+                                             int async);
+
 int tcp_start_incoming_migration(const char *host_port);
 
 MigrationState *tcp_start_outgoing_migration(const char *host_port,
@@ -89,6 +95,12 @@ void migrate_fd_wait_for_unfreeze(void *opaque);
 
 int migrate_fd_close(void *opaque);
 
+int migrate_file_errno(FdMigrationState *s);
+
+int migrate_file_write(FdMigrationState *s, const void * buf, size_t size);
+
+int migrate_file_close(FdMigrationState *s);
+
 static inline FdMigrationState *migrate_to_fms(MigrationState *mig_state)
 {
     return container_of(mig_state, FdMigrationState, mig_state);
diff --git a/savevm.c b/savevm.c
index 1ee5a6f..8f5fd16 100644
--- a/savevm.c
+++ b/savevm.c
@@ -226,7 +226,6 @@ QEMUFile *qemu_popen(FILE *popen_file, const char *mode)
     } else {
         s->file = qemu_fopen_ops(s, popen_put_buffer, NULL, popen_close, NULL);
     }
-    fprintf(stderr, "qemu_popen: returning result of qemu_fopen_ops\n");
     return s->file;
 }
 
@@ -283,6 +282,30 @@ static int file_close(void *opaque)
     return 0;
 }
 
+QEMUFile *qemu_fdopen(int fd, const char *mode)
+{
+    QEMUFileStdio *s;
+
+    s = qemu_mallocz(sizeof(QEMUFileStdio));
+    if (!s)
+        return NULL;
+
+    s->outfile = fdopen(fd, mode);
+    if (!s->outfile)
+        goto fail;
+
+    if (!strcmp(mode, "wb"))
+        return qemu_fopen_ops(s, file_put_buffer, NULL, file_close, NULL);
+    else if (!strcmp(mode, "rb"))
+        return qemu_fopen_ops(s, NULL, file_get_buffer, file_close, NULL);
+
+fail:
+    if (s->outfile)
+        fclose(s->outfile);
+    qemu_free(s);
+    return NULL;
+}
+
 QEMUFile *qemu_fopen(const char *filename, const char *mode)
 {
     QEMUFileStdio *s;