[Qemu-devel] [PATCH] add file: migration support

[Qemu-devel] [PATCH] add file: migration support

[Charles Duffy]

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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().

Signed-off-by: Charles Duffy <charles_duffy@messageone.com>

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diff --git a/.gitignore b/.gitignore
index e70ebab..8e28325 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,4 +30,4 @@ qemu-nbd.8
 *.tp
 *.vr
 *.d
-
+*.o
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..7240b36
--- /dev/null
+++ b/migration-file.c
@@ -0,0 +1,119 @@
+/*
+ * 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;
+    }
+
+    s->fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC, 0666);
+    if (s->fd == -1) {
+        perror("Unable to open migration target");
+        goto err_after_alloc;
+    }
+
+    if (fcntl(s->fd, F_SETFD, O_NONBLOCK) == -1) {
+        dprintf("Unable to set nonblocking mode on file descriptor\n");
+        goto err_after_open;
+    }
+
+    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_open:
+    close(s->fd);
+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;

[Qemu-devel] Re: [PATCH] add file: migration support

[Charles Duffy]

Oops -- didn't mean to include my local .gitignore changes in that.

Re: [Qemu-devel] [PATCH] add file: migration support

[Anthony Liguori]

Charles Duffy wrote:
> 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().
>
> Signed-off-by: Charles Duffy <charles_duffy@messageone.com>
> diff --git a/.gitignore b/.gitignore
> index e70ebab..8e28325 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -30,4 +30,4 @@ qemu-nbd.8
>  *.tp
>  *.vr
>  *.d
> -
> +*.o
>   

Please keep this sort of stuff separate from a general patch.

> +    s->fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC, 0666);
> +    if (s->fd == -1) {
> +        perror("Unable to open migration target");
> +        goto err_after_alloc;
> +    }
> +
> +    if (fcntl(s->fd, F_SETFD, O_NONBLOCK) == -1) {
> +        dprintf("Unable to set nonblocking mode on file descriptor\n");
> +        goto err_after_open;
> +    }
>   

Did you mean F_SETFL?

At any rate, this doesn't do what you think it does.  O_NONBLOCK still 
blocks with a file.  To implement a proper file: migration protocol, you 
have to use something like posix-aio to write to the file asychronously.

You can observe the problem here by setting the migration data limit to 
something very, very high (like 10GB).  That will cause the VM to become 
unresponsive until all the data is on disk which is certainly not live 
migration.

Regards,

Anthony Liguori