Re: [RFC][PATCH] Use ioemu block drivers through blktap

[Kevin Wolf <kwolf@suse.de>]

[-- Attachment #1: Type: text/plain, Size: 2230 bytes --]

Hi Konrad,

first of all, thank you for your review. You noticed quite a few points
I never really looked at because I inherited them from the current
tapdisk code. But probably I should fix these issues as well. ;-)

Konrad Rzeszutek schrieb:
>> +	blkif->fds[READ] = open_ctrl_socket(wrctldev);
>> +	blkif->fds[WRITE] = open_ctrl_socket(rdctldev);
> 
> How about freeing the data here once?
> 
>> +	
>> +	if (blkif->fds[READ] == -1 || blkif->fds[WRITE] == -1) {
>> +		free(rdctldev);
>> +		free(wrctldev);
> 
> And then this is not needed.
> 
>> +		return -1;
>> +	}
>> +
>> +	DPRINTF("Attached to qemu blktap pipes\n");
>> +	free(rdctldev);
>> +	free(wrctldev);
> 
> Nor these two lines above.

Hmm, good point. This code looks a bit silly... Will move the free to
the place you suggested.

>> --- a/tools/python/xen/xend/server/BlktapController.py	Mon Mar 10 22:51:57 2008 +0000
>> +++ b/tools/python/xen/xend/server/BlktapController.py	Thu Mar 13 13:00:18 2008 +0100
>> @@ -13,7 +13,9 @@ blktap_disk_types = [
>>      'vmdk',
>>      'ram',
>>      'qcow',
>> -    'qcow2'
>> +    'qcow2',
>> +
>> +    'ioemu'
> 
> Why add the extra \n ?

I wanted to separate the ioemu pseudo driver (which is the only one that
doesn't go through tapdisk) from the "real" tapdisk drivers.

>> +static struct td_state *state_init(void)
>> +{
>> +	int i;
>> +	struct td_state *s;
>> +	blkif_t *blkif;
>> +
>> +	s = malloc(sizeof(struct td_state));
> 
> Would it make sense to zero out the allocated memory?

This code comes directly from tapdisk and it worked there. On the other
hand, it certainly wouldn't hurt.

>> +			switch (req->operation) 
>> +			{
>> +			case BLKIF_OP_WRITE:
>> +				aiocb_info = malloc(sizeof(*aiocb_info));
>> +
>> +				aiocb_info->s = s;
>> +				aiocb_info->sector = sector_nr;
>> +				aiocb_info->nr_secs = nsects;
>> +				aiocb_info->idx = idx;
>> +				aiocb_info->i = i;
>> +
>> +				ret = (NULL == bdrv_aio_write(s->bs, sector_nr,
>> +							  page, nsects,
>> +							  qemu_send_responses,
>> +							  aiocb_info));
> 
> Who de-allocates aiocb_info?

qemu_send_responses is a callback function which gets aiocb_info as
parameter and frees it when it's done.

I've attached a new version of the patch.

Kevin

[-- Attachment #2: blktap-ioemu.patch --]
[-- Type: text/x-patch, Size: 24663 bytes --]

diff -r 7530c4dba8a5 tools/blktap/drivers/blktapctrl.c
--- a/tools/blktap/drivers/blktapctrl.c	Mon Mar  3 15:19:39 2008
+++ b/tools/blktap/drivers/blktapctrl.c	Fri Mar 14 11:14:10 2008
@@ -501,6 +501,80 @@
 	return 0;
 }
 
+/* Connect to qemu-dm */
+static int connect_qemu(blkif_t *blkif)
+{
+	char *rdctldev, *wrctldev;
+	
+	if (asprintf(&rdctldev, BLKTAP_CTRL_DIR "/qemu-read-%d", 
+			blkif->domid) < 0)
+		return -1;
+
+	if (asprintf(&wrctldev, BLKTAP_CTRL_DIR "/qemu-write-%d", 
+			blkif->domid) < 0) {
+		free(rdctldev);
+		return -1;
+	}
+
+	DPRINTF("Using qemu blktap pipe: %s\n", rdctldev);
+	
+	blkif->fds[READ] = open_ctrl_socket(wrctldev);
+	blkif->fds[WRITE] = open_ctrl_socket(rdctldev);
+	
+	free(rdctldev);
+	free(wrctldev);
+	
+	if (blkif->fds[READ] == -1 || blkif->fds[WRITE] == -1)
+		return -1;
+
+	DPRINTF("Attached to qemu blktap pipes\n");
+	return 0;
+}
+
+/* Launch tapdisk instance */
+static int connect_tapdisk(blkif_t *blkif, int minor)
+{
+	char *rdctldev = NULL, *wrctldev = NULL;
+	int ret = -1;
+
+	DPRINTF("tapdisk process does not exist:\n");
+
+	if (asprintf(&rdctldev,
+		     "%s/tapctrlread%d", BLKTAP_CTRL_DIR, minor) == -1)
+		goto fail;
+
+	if (asprintf(&wrctldev,
+		     "%s/tapctrlwrite%d", BLKTAP_CTRL_DIR, minor) == -1)
+		goto fail;
+	
+	blkif->fds[READ] = open_ctrl_socket(rdctldev);
+	blkif->fds[WRITE] = open_ctrl_socket(wrctldev);
+	
+	if (blkif->fds[READ] == -1 || blkif->fds[WRITE] == -1)
+		goto fail;
+
+	/*launch the new process*/
+	DPRINTF("Launching process, CMDLINE [tapdisk %s %s]\n",
+			wrctldev, rdctldev);
+
+	if (launch_tapdisk(wrctldev, rdctldev) == -1) {
+		DPRINTF("Unable to fork, cmdline: [tapdisk %s %s]\n",
+				wrctldev, rdctldev);
+		goto fail;
+	}
+
+	ret = 0;
+	
+fail:
+	if (rdctldev)
+		free(rdctldev);
+
+	if (wrctldev)
+		free(wrctldev);
+
+	return ret;
+}
+
 int blktapctrl_new_blkif(blkif_t *blkif)
 {
 	blkif_info_t *blk;
@@ -524,30 +598,14 @@
 		blkif->cookie = next_cookie++;
 
 		if (!exist) {
-			DPRINTF("Process does not exist:\n");
-			if (asprintf(&rdctldev,
-				     "%s/tapctrlread%d", BLKTAP_CTRL_DIR, minor) == -1)
-				goto fail;
-			if (asprintf(&wrctldev,
-				     "%s/tapctrlwrite%d", BLKTAP_CTRL_DIR, minor) == -1) {
-				free(rdctldev);
-				goto fail;
+			if (type == DISK_TYPE_IOEMU) {
+				if (connect_qemu(blkif))
+					goto fail;
+			} else {
+				if (connect_tapdisk(blkif, minor))
+					goto fail;
 			}
-			blkif->fds[READ] = open_ctrl_socket(rdctldev);
-			blkif->fds[WRITE] = open_ctrl_socket(wrctldev);
-			
-			if (blkif->fds[READ] == -1 || blkif->fds[WRITE] == -1) 
-				goto fail;
-
-			/*launch the new process*/
- 			DPRINTF("Launching process, CMDLINE [tapdisk %s %s]\n",wrctldev, rdctldev);
- 			if (launch_tapdisk(wrctldev, rdctldev) == -1) {
- 				DPRINTF("Unable to fork, cmdline: [tapdisk %s %s]\n",wrctldev, rdctldev);
-				goto fail;
-			}
-
-			free(rdctldev);
-			free(wrctldev);
+
 		} else {
 			DPRINTF("Process exists!\n");
 			blkif->fds[READ] = exist->fds[READ];
diff -r 7530c4dba8a5 tools/blktap/drivers/tapdisk.h
--- a/tools/blktap/drivers/tapdisk.h	Mon Mar  3 15:19:39 2008
+++ b/tools/blktap/drivers/tapdisk.h	Fri Mar 14 11:14:10 2008
@@ -167,6 +167,7 @@
 #define DISK_TYPE_RAM      3
 #define DISK_TYPE_QCOW     4
 #define DISK_TYPE_QCOW2    5
+#define DISK_TYPE_IOEMU    6
 
 
 /*Define Individual Disk Parameters here */
@@ -227,6 +228,16 @@
 	0,
 #ifdef TAPDISK
 	&tapdisk_qcow2,
+#endif
+};
+
+static disk_info_t ioemu_disk = {
+	DISK_TYPE_IOEMU,
+	"ioemu disk",
+	"ioemu",
+	0,
+#ifdef TAPDISK
+	NULL
 #endif
 };
 
@@ -238,6 +249,7 @@
 	&ram_disk,
 	&qcow_disk,
 	&qcow2_disk,
+	&ioemu_disk,
 };
 
 typedef struct driver_list_entry {
diff -r 7530c4dba8a5 tools/blktap/lib/blktaplib.h
--- a/tools/blktap/lib/blktaplib.h	Mon Mar  3 15:19:39 2008
+++ b/tools/blktap/lib/blktaplib.h	Fri Mar 14 11:14:10 2008
@@ -221,15 +221,5 @@
      ((_req) * BLKIF_MAX_SEGMENTS_PER_REQUEST * getpagesize()) +    \
      ((_seg) * getpagesize()))
 
-/* Defines that are only used by library clients */
-
-#ifndef __COMPILING_BLKTAP_LIB
-
-static char *blkif_op_name[] = {
-	[BLKIF_OP_READ]       = "READ",
-	[BLKIF_OP_WRITE]      = "WRITE",
-};
-
-#endif /* __COMPILING_BLKTAP_LIB */
 
 #endif /* __BLKTAPLIB_H__ */
diff -r 7530c4dba8a5 tools/ioemu/Makefile.target
--- a/tools/ioemu/Makefile.target	Mon Mar  3 15:19:39 2008
+++ b/tools/ioemu/Makefile.target	Fri Mar 14 11:14:10 2008
@@ -17,6 +17,7 @@
 VPATH=$(SRC_PATH):$(TARGET_PATH):$(SRC_PATH)/hw:$(SRC_PATH)/audio
 CPPFLAGS+=-I. -I.. -I$(TARGET_PATH) -I$(SRC_PATH)
 CPPFLAGS+= -I$(XEN_ROOT)/tools/libxc
+CPPFLAGS+= -I$(XEN_ROOT)/tools/blktap/lib
 CPPFLAGS+= -I$(XEN_ROOT)/tools/xenstore
 CPPFLAGS+= -I$(XEN_ROOT)/tools/include
 ifdef CONFIG_DARWIN_USER
@@ -429,6 +430,7 @@
 VL_OBJS+= usb-uhci.o smbus_eeprom.o
 VL_OBJS+= piix4acpi.o
 VL_OBJS+= xenstore.o
+VL_OBJS+= xen_blktap.o
 VL_OBJS+= xen_platform.o
 VL_OBJS+= xen_machine_fv.o
 VL_OBJS+= xen_machine_pv.o
diff -r 7530c4dba8a5 tools/ioemu/hw/xen_machine_pv.c
--- a/tools/ioemu/hw/xen_machine_pv.c	Mon Mar  3 15:19:39 2008
+++ b/tools/ioemu/hw/xen_machine_pv.c	Fri Mar 14 11:14:10 2008
@@ -26,6 +26,9 @@
 #include "xen_console.h"
 #include "xenfb.h"
 
+extern void init_blktap(void);
+
+
 /* The Xen PV machine currently provides
  *   - a virtual framebuffer
  *   - ....
@@ -40,6 +43,10 @@
 {
     struct xenfb *xenfb;
     extern int domid;
+
+
+    /* Initialize tapdisk client */
+    init_blktap();
 
     /* Connect to text console */
     if (serial_hds[0]) {
diff -r 7530c4dba8a5 tools/ioemu/vl.c
--- a/tools/ioemu/vl.c	Mon Mar  3 15:19:39 2008
+++ b/tools/ioemu/vl.c	Fri Mar 14 11:14:10 2008
@@ -6266,6 +6266,12 @@
     powerdown_requested = 1;
     if (cpu_single_env)
         cpu_interrupt(cpu_single_env, CPU_INTERRUPT_EXIT);
+}
+
+static void qemu_sighup_handler(int signal)
+{
+    fprintf(stderr, "Received SIGHUP, terminating.\n");
+    exit(0);
 }
 
 void main_loop_wait(int timeout)
@@ -7976,7 +7982,7 @@
 
 #ifndef CONFIG_STUBDOM
     /* Unblock SIGTERM and SIGHUP, which may have been blocked by the caller */
-    signal(SIGHUP, SIG_DFL);
+    signal(SIGHUP, qemu_sighup_handler);
     sigemptyset(&set);
     sigaddset(&set, SIGTERM);
     sigaddset(&set, SIGHUP);
diff -r 7530c4dba8a5 tools/python/xen/xend/server/BlktapController.py
--- a/tools/python/xen/xend/server/BlktapController.py	Mon Mar  3 15:19:39 2008
+++ b/tools/python/xen/xend/server/BlktapController.py	Fri Mar 14 11:14:10 2008
@@ -13,7 +13,9 @@
     'vmdk',
     'ram',
     'qcow',
-    'qcow2'
+    'qcow2',
+
+    'ioemu'
     ]
 
 class BlktapController(BlkifController):
diff -r 7530c4dba8a5 tools/ioemu/hw/xen_blktap.c
--- /dev/null	Mon Mar  3 15:19:39 2008
+++ b/tools/ioemu/hw/xen_blktap.c	Fri Mar 14 11:14:10 2008
@@ -0,0 +1,686 @@
+/* xen_blktap.c
+ *
+ * Interface to blktapctrl to allow use of qemu block drivers with blktap.
+ * This file is based on tools/blktap/drivers/tapdisk.c
+ * 
+ * Copyright (c) 2005 Julian Chesterfield and Andrew Warfield.
+ * Copyright (c) 2008 Kevin Wolf
+ */
+
+/*
+ * There are several communication channels which are used by this interface:
+ *
+ *   - A pair of pipes for receiving and sending general control messages
+ *     (qemu-read-N and qemu-writeN in /var/run/tap, where N is the domain ID).
+ *     These control messages are handled by handle_blktap_ctrlmsg().
+ *
+ *   - One file descriptor per attached disk (/dev/xen/blktapN) for disk
+ *     specific control messages. A callback is triggered on this fd if there
+ *     is a new IO request. The callback function is handle_blktap_iomsg().
+ *
+ *   - A shared ring for each attached disk containing the actual IO requests 
+ *     and responses. Whenever handle_blktap_iomsg() is triggered it processes
+ *     the requests on this ring.
+ */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include "vl.h"
+#include "blktaplib.h"
+#include "xen_blktap.h"
+#include "block_int.h"
+
+#define MSG_SIZE 4096
+
+#define BLKTAP_CTRL_DIR "/var/run/tap"
+
+/* If enabled, print debug messages to stderr */
+#if 1
+#define DPRINTF(_f, _a...) fprintf(stderr, __FILE__ ":%d: " _f, __LINE__, ##_a)
+#else
+#define DPRINTF(_f, _a...) ((void)0)
+#endif
+
+#if 1                                                                        
+#define ASSERT(_p) \
+    if ( !(_p) ) { DPRINTF("Assertion '%s' failed, line %d, file %s\n", #_p , \
+        __LINE__, __FILE__); *(int*)0=0; }
+#else
+#define ASSERT(_p) ((void)0)
+#endif 
+
+
+extern int domid;
+
+int read_fd;
+int write_fd;
+
+static pid_t process;
+fd_list_entry_t *fd_start = NULL;
+
+static void handle_blktap_iomsg(void* private);
+
+struct aiocb_info {
+	struct td_state	*s;
+	uint64_t sector;
+	int nr_secs;
+	int idx;
+	long i;
+};
+
+static void unmap_disk(struct td_state *s)
+{
+	tapdev_info_t *info = s->ring_info;
+	fd_list_entry_t *entry;
+	
+	bdrv_close(s->bs);
+
+	if (info != NULL && info->mem > 0)
+	        munmap(info->mem, getpagesize() * BLKTAP_MMAP_REGION_SIZE);
+
+	entry = s->fd_entry;
+	*entry->pprev = entry->next;
+	if (entry->next)
+		entry->next->pprev = entry->pprev;
+
+	qemu_set_fd_handler2(info->fd, NULL, NULL, NULL, NULL);
+	close(info->fd);
+
+	free(s->fd_entry);
+	free(s->blkif);
+	free(s->ring_info);
+	free(s);
+
+	return;
+}
+
+static inline fd_list_entry_t *add_fd_entry(int tap_fd, struct td_state *s)
+{
+	fd_list_entry_t **pprev, *entry;
+
+	DPRINTF("Adding fd_list_entry\n");
+
+	/*Add to linked list*/
+	s->fd_entry   = entry = malloc(sizeof(fd_list_entry_t));
+	entry->tap_fd = tap_fd;
+	entry->s      = s;
+	entry->next   = NULL;
+
+	pprev = &fd_start;
+	while (*pprev != NULL)
+		pprev = &(*pprev)->next;
+
+	*pprev = entry;
+	entry->pprev = pprev;
+
+	return entry;
+}
+
+static inline struct td_state *get_state(int cookie)
+{
+	fd_list_entry_t *ptr;
+
+	ptr = fd_start;
+	while (ptr != NULL) {
+		if (ptr->cookie == cookie) return ptr->s;
+		ptr = ptr->next;
+	}
+	return NULL;
+}
+
+static struct td_state *state_init(void)
+{
+	int i;
+	struct td_state *s;
+	blkif_t *blkif;
+
+	s = malloc(sizeof(struct td_state));
+	blkif = s->blkif = malloc(sizeof(blkif_t));
+	s->ring_info = calloc(1, sizeof(tapdev_info_t));
+
+	for (i = 0; i < MAX_REQUESTS; i++) {
+		blkif->pending_list[i].secs_pending = 0;
+		blkif->pending_list[i].submitting = 0;
+	}
+
+	return s;
+}
+
+static int map_new_dev(struct td_state *s, int minor)
+{
+	int tap_fd;
+	tapdev_info_t *info = s->ring_info;
+	char *devname;
+	fd_list_entry_t *ptr;
+	int page_size;
+
+	if (asprintf(&devname,"%s/%s%d", BLKTAP_DEV_DIR, BLKTAP_DEV_NAME, minor) == -1)
+		return -1;
+	tap_fd = open(devname, O_RDWR);
+	if (tap_fd == -1) 
+	{
+		DPRINTF("open failed on dev %s!\n",devname);
+		goto fail;
+	} 
+	info->fd = tap_fd;
+
+	/*Map the shared memory*/
+	page_size = getpagesize();
+	info->mem = mmap(0, page_size * BLKTAP_MMAP_REGION_SIZE, 
+			  PROT_READ | PROT_WRITE, MAP_SHARED, info->fd, 0);
+	if ((long int)info->mem == -1) 
+	{
+		DPRINTF("mmap failed on dev %s!\n",devname);
+		goto fail;
+	}
+
+	/* assign the rings to the mapped memory */ 
+	info->sring = (blkif_sring_t *)((unsigned long)info->mem);
+	BACK_RING_INIT(&info->fe_ring, info->sring, page_size);
+	
+	info->vstart = 
+	        (unsigned long)info->mem + (BLKTAP_RING_PAGES * page_size);
+
+	ioctl(info->fd, BLKTAP_IOCTL_SENDPID, process );
+	ioctl(info->fd, BLKTAP_IOCTL_SETMODE, BLKTAP_MODE_INTERPOSE );
+	free(devname);
+
+	/*Update the fd entry*/
+	ptr = fd_start;
+	while (ptr != NULL) {
+		if (s == ptr->s) {
+			ptr->tap_fd = tap_fd;
+
+			/* Setup fd_handler for qemu main loop */
+			DPRINTF("set tap_fd = %d\n", tap_fd);
+			qemu_set_fd_handler2(tap_fd, NULL, &handle_blktap_iomsg, NULL, s);
+
+			break;
+		}
+		ptr = ptr->next;
+	}	
+
+
+	DPRINTF("map_new_dev = %d\n", minor);
+	return minor;
+
+ fail:
+	free(devname);
+	return -1;
+}
+
+static int open_disk(struct td_state *s, char *path, int readonly)
+{
+	struct disk_id id;
+	BlockDriverState* bs;
+
+	DPRINTF("Opening %s\n", path);
+	bs = calloc(1, sizeof(*bs));
+
+	memset(&id, 0, sizeof(struct disk_id));
+
+	if (bdrv_open(bs, path, 0) != 0) {
+		fprintf(stderr, "Could not open image file %s\n", path);
+		return -ENOMEM;
+	}
+
+	s->bs = bs;
+	s->flags = readonly ? TD_RDONLY : 0;
+	s->size = bs->total_sectors;
+	s->sector_size = 512;
+
+	s->info = ((s->flags & TD_RDONLY) ? VDISK_READONLY : 0);
+
+	return 0;
+}
+
+static inline void write_rsp_to_ring(struct td_state *s, blkif_response_t *rsp)
+{
+	tapdev_info_t *info = s->ring_info;
+	blkif_response_t *rsp_d;
+	
+	rsp_d = RING_GET_RESPONSE(&info->fe_ring, info->fe_ring.rsp_prod_pvt);
+	memcpy(rsp_d, rsp, sizeof(blkif_response_t));
+	info->fe_ring.rsp_prod_pvt++;
+}
+
+static inline void kick_responses(struct td_state *s)
+{
+	tapdev_info_t *info = s->ring_info;
+
+	if (info->fe_ring.rsp_prod_pvt != info->fe_ring.sring->rsp_prod) 
+	{
+		RING_PUSH_RESPONSES(&info->fe_ring);
+		ioctl(info->fd, BLKTAP_IOCTL_KICK_FE);
+	}
+}
+
+static int send_responses(struct td_state *s, int res, 
+		   uint64_t sector, int nr_secs, int idx, void *private)
+{
+	pending_req_t   *preq;
+	blkif_request_t *req;
+	int responses_queued = 0;
+	blkif_t *blkif = s->blkif;
+	int secs_done = nr_secs;
+
+	if ( (idx > MAX_REQUESTS-1) )
+	{
+		DPRINTF("invalid index returned(%u)!\n", idx);
+		return 0;
+	}
+	preq = &blkif->pending_list[idx];
+	req  = &preq->req;
+
+	preq->secs_pending -= secs_done;
+
+	if (res == -EBUSY && preq->submitting) 
+		return -EBUSY;  /* propagate -EBUSY back to higher layers */
+	if (res) 
+		preq->status = BLKIF_RSP_ERROR;
+	
+	if (!preq->submitting && preq->secs_pending == 0) 
+	{
+		blkif_request_t tmp;
+		blkif_response_t *rsp;
+
+		tmp = preq->req;
+		rsp = (blkif_response_t *)req;
+		
+		rsp->id = tmp.id;
+		rsp->operation = tmp.operation;
+		rsp->status = preq->status;
+		
+		write_rsp_to_ring(s, rsp);
+		responses_queued++;
+
+		kick_responses(s);
+	}
+	
+	return responses_queued;
+}
+
+static void qemu_send_responses(void* opaque, int ret)
+{
+	struct aiocb_info* info = opaque;
+
+	if (ret != 0) {
+		DPRINTF("ERROR: ret = %d (%s)\n", ret, strerror(-ret));
+	}
+
+	send_responses(info->s, ret, info->sector, info->nr_secs, 
+		info->idx, (void*) info->i);
+	free(info);
+}
+
+/**
+ * Callback function for the IO message pipe. Reads requests from the ring
+ * and processes them (call qemu read/write functions).
+ *
+ * The private parameter points to the struct td_state representing the
+ * disk the request is targeted at.
+ */
+static void handle_blktap_iomsg(void* private)
+{
+	struct td_state* s = private;
+
+	RING_IDX          rp, j, i;
+	blkif_request_t  *req;
+	int idx, nsects, ret;
+	uint64_t sector_nr;
+	uint8_t *page;
+	blkif_t *blkif = s->blkif;
+	tapdev_info_t *info = s->ring_info;
+	int page_size = getpagesize();
+
+	struct aiocb_info *aiocb_info;
+
+	if (info->fe_ring.sring == NULL) {
+		DPRINTF("  sring == NULL, ignoring IO request\n");
+		return;
+	}
+
+	rp = info->fe_ring.sring->req_prod; 
+	xen_rmb();
+
+	for (j = info->fe_ring.req_cons; j != rp; j++)
+	{
+		int start_seg = 0; 
+
+		req = NULL;
+		req = RING_GET_REQUEST(&info->fe_ring, j);
+		++info->fe_ring.req_cons;
+		
+		if (req == NULL)
+			continue;
+
+		idx = req->id;
+
+		ASSERT(blkif->pending_list[idx].secs_pending == 0);
+		memcpy(&blkif->pending_list[idx].req, req, sizeof(*req));
+		blkif->pending_list[idx].status = BLKIF_RSP_OKAY;
+		blkif->pending_list[idx].submitting = 1;
+		sector_nr = req->sector_number;
+
+		/* Don't allow writes on readonly devices */
+		if ((s->flags & TD_RDONLY) && 
+		    (req->operation == BLKIF_OP_WRITE)) {
+			blkif->pending_list[idx].status = BLKIF_RSP_ERROR;
+			goto send_response;
+		}
+
+		for (i = start_seg; i < req->nr_segments; i++) {
+			nsects = req->seg[i].last_sect - 
+				 req->seg[i].first_sect + 1;
+	
+			if ((req->seg[i].last_sect >= page_size >> 9) ||
+					(nsects <= 0))
+				continue;
+
+			page  = (uint8_t*) MMAP_VADDR(info->vstart, 
+						   (unsigned long)req->id, i);
+			page += (req->seg[i].first_sect << SECTOR_SHIFT);
+
+			if (sector_nr >= s->size) {
+				DPRINTF("Sector request failed:\n");
+				DPRINTF("%s request, idx [%d,%d] size [%llu], "
+					"sector [%llu,%llu]\n",
+					(req->operation == BLKIF_OP_WRITE ? 
+					 "WRITE" : "READ"),
+					idx,i,
+					(long long unsigned) 
+						nsects<<SECTOR_SHIFT,
+					(long long unsigned) 
+						sector_nr<<SECTOR_SHIFT,
+					(long long unsigned) sector_nr);
+				continue;
+			}
+
+			blkif->pending_list[idx].secs_pending += nsects;
+
+			switch (req->operation) 
+			{
+			case BLKIF_OP_WRITE:
+				aiocb_info = malloc(sizeof(*aiocb_info));
+
+				aiocb_info->s = s;
+				aiocb_info->sector = sector_nr;
+				aiocb_info->nr_secs = nsects;
+				aiocb_info->idx = idx;
+				aiocb_info->i = i;
+
+				ret = (NULL == bdrv_aio_write(s->bs, sector_nr,
+							  page, nsects,
+							  qemu_send_responses,
+							  aiocb_info));
+
+				if (ret) {
+					blkif->pending_list[idx].status = BLKIF_RSP_ERROR;
+					DPRINTF("ERROR: bdrv_write() == NULL\n");
+					goto send_response;
+				}
+				break;
+
+			case BLKIF_OP_READ:
+				aiocb_info = malloc(sizeof(*aiocb_info));
+
+				aiocb_info->s = s;
+				aiocb_info->sector = sector_nr;
+				aiocb_info->nr_secs = nsects;
+				aiocb_info->idx = idx;
+				aiocb_info->i = i;
+
+				ret = (NULL == bdrv_aio_read(s->bs, sector_nr,
+							 page, nsects,
+							 qemu_send_responses,
+							 aiocb_info));
+
+				if (ret) {
+					blkif->pending_list[idx].status = BLKIF_RSP_ERROR;
+					DPRINTF("ERROR: bdrv_read() == NULL\n");
+					goto send_response;
+				}
+				break;
+
+			default:
+				DPRINTF("Unknown block operation\n");
+				break;
+			}
+			sector_nr += nsects;
+		}
+	send_response:
+		blkif->pending_list[idx].submitting = 0;
+
+		/* force write_rsp_to_ring for synchronous case */
+		if (blkif->pending_list[idx].secs_pending == 0)
+			send_responses(s, 0, 0, 0, idx, (void *)(long)0);
+	}
+}
+
+/**
+ * Callback function for the qemu-read pipe. Reads and processes control 
+ * message from the pipe.
+ *
+ * The parameter private is unused.
+ */
+static void handle_blktap_ctrlmsg(void* private)
+{
+	int length, len, msglen;
+	char *ptr, *path;
+	image_t *img;
+	msg_hdr_t *msg;
+	msg_newdev_t *msg_dev;
+	msg_pid_t *msg_pid;
+	int ret = -1;
+	struct td_state *s = NULL;
+	fd_list_entry_t *entry;
+
+	char buf[MSG_SIZE];
+
+	length = read(read_fd, buf, MSG_SIZE);
+
+	if (length > 0 && length >= sizeof(msg_hdr_t)) 
+	{
+		msg = (msg_hdr_t *)buf;
+		DPRINTF("blktap: Received msg, len %d, type %d, UID %d\n",
+			length,msg->type,msg->cookie);
+
+		switch (msg->type) {
+		case CTLMSG_PARAMS: 			
+			ptr = buf + sizeof(msg_hdr_t);
+			len = (length - sizeof(msg_hdr_t));
+			path = calloc(1, len + 1);
+			
+			memcpy(path, ptr, len); 
+			DPRINTF("Received CTLMSG_PARAMS: [%s]\n", path);
+
+			/* Allocate the disk structs */
+			s = state_init();
+
+			/*Open file*/
+			if (s == NULL || open_disk(s, path, msg->readonly)) {
+				msglen = sizeof(msg_hdr_t);
+				msg->type = CTLMSG_IMG_FAIL;
+				msg->len = msglen;
+			} else {
+				entry = add_fd_entry(0, s);
+				entry->cookie = msg->cookie;
+				DPRINTF("Entered cookie %d\n", entry->cookie);
+				
+				memset(buf, 0x00, MSG_SIZE); 
+			
+				msglen = sizeof(msg_hdr_t) + sizeof(image_t);
+				msg->type = CTLMSG_IMG;
+				img = (image_t *)(buf + sizeof(msg_hdr_t));
+				img->size = s->size;
+				img->secsize = s->sector_size;
+				img->info = s->info;
+				DPRINTF("Writing (size, secsize, info) = "
+					"(%#" PRIx64 ", %#" PRIx64 ", %d)\n",
+					s->size, s->sector_size, s->info);
+			}
+			len = write(write_fd, buf, msglen);
+			free(path);
+			break;
+			
+		case CTLMSG_NEWDEV:
+			msg_dev = (msg_newdev_t *)(buf + sizeof(msg_hdr_t));
+
+			s = get_state(msg->cookie);
+			DPRINTF("Retrieving state, cookie %d.....[%s]\n",
+				msg->cookie, (s == NULL ? "FAIL":"OK"));
+			if (s != NULL) {
+				ret = ((map_new_dev(s, msg_dev->devnum) 
+					== msg_dev->devnum ? 0: -1));
+			}	
+
+			memset(buf, 0x00, MSG_SIZE); 
+			msglen = sizeof(msg_hdr_t);
+			msg->type = (ret == 0 ? CTLMSG_NEWDEV_RSP 
+				              : CTLMSG_NEWDEV_FAIL);
+			msg->len = msglen;
+
+			len = write(write_fd, buf, msglen);
+			break;
+
+		case CTLMSG_CLOSE:
+			s = get_state(msg->cookie);
+			if (s) unmap_disk(s);
+			break;			
+
+		case CTLMSG_PID:
+			memset(buf, 0x00, MSG_SIZE);
+			msglen = sizeof(msg_hdr_t) + sizeof(msg_pid_t);
+			msg->type = CTLMSG_PID_RSP;
+			msg->len = msglen;
+
+			msg_pid = (msg_pid_t *)(buf + sizeof(msg_hdr_t));
+			process = getpid();
+			msg_pid->pid = process;
+
+			len = write(write_fd, buf, msglen);
+			break;
+
+		default:
+			break;
+		}
+	}
+}
+
+/**
+ * Opens a control socket, i.e. a pipe to communicate with blktapctrl.
+ *
+ * Returns the file descriptor number for the pipe; -1 in error case
+ */
+static int open_ctrl_socket(char *devname)
+{
+	int ret;
+	int ipc_fd;
+
+	if (mkdir(BLKTAP_CTRL_DIR, 0755) == 0)
+		DPRINTF("Created %s directory\n", BLKTAP_CTRL_DIR);
+
+	ret = mkfifo(devname,S_IRWXU|S_IRWXG|S_IRWXO);
+	if ( (ret != 0) && (errno != EEXIST) ) {
+		DPRINTF("ERROR: pipe failed (%d)\n", errno);
+		return -1;
+	}
+
+	ipc_fd = open(devname,O_RDWR|O_NONBLOCK);
+
+	if (ipc_fd < 0) {
+		DPRINTF("FD open failed\n");
+		return -1;
+	}
+
+	return ipc_fd;
+}
+
+/**
+ * Unmaps all disks and closes their pipes
+ */
+void shutdown_blktap(void)
+{
+	fd_list_entry_t *ptr;
+	struct td_state *s;
+	char *devname;
+
+	DPRINTF("Shutdown blktap\n");
+
+	/* Unmap all disks */
+	ptr = fd_start;
+	while (ptr != NULL) {
+		s = ptr->s;
+		unmap_disk(s);
+		close(ptr->tap_fd);
+		ptr = ptr->next;
+	}
+
+	/* Delete control pipes */
+	if (asprintf(&devname, BLKTAP_CTRL_DIR "/qemu-read-%d", domid) >= 0) {
+		DPRINTF("Delete %s\n", devname);
+		if (unlink(devname))
+			DPRINTF("Could not delete: %s\n", strerror(errno));
+		free(devname);
+	}
+	
+	if (asprintf(&devname, BLKTAP_CTRL_DIR "/qemu-write-%d", domid) >= 0) {	
+		DPRINTF("Delete %s\n", devname);
+		if (unlink(devname))
+			DPRINTF("Could not delete: %s\n", strerror(errno));
+		free(devname);
+	}
+}
+
+/**
+ * Initialize the blktap interface, i.e. open a pair of pipes in /var/run/tap
+ * and register a fd handler.
+ *
+ * Returns 0 on success.
+ */
+int init_blktap(void)
+{
+	char* devname;	
+
+	DPRINTF("Init blktap pipes\n");
+
+	/* Open the read pipe */
+	if (asprintf(&devname, BLKTAP_CTRL_DIR "/qemu-read-%d", domid) >= 0) {	
+		read_fd = open_ctrl_socket(devname);		
+		free(devname);
+		
+		if (read_fd == -1) {
+			fprintf(stderr, "Could not open %s/qemu-read-%d\n",
+				BLKTAP_CTRL_DIR, domid);
+			return -1;
+		}
+	}
+	
+	/* Open the write pipe */
+	if (asprintf(&devname, BLKTAP_CTRL_DIR "/qemu-write-%d", domid) >= 0) {
+		write_fd = open_ctrl_socket(devname);
+		free(devname);
+		
+		if (write_fd == -1) {
+			fprintf(stderr, "Could not open %s/qemu-write-%d\n",
+				BLKTAP_CTRL_DIR, domid);
+			close(read_fd);
+			return -1;
+		}
+	}
+
+	/* Attach a handler to the read pipe (called from qemu main loop) */
+	qemu_set_fd_handler2(read_fd, NULL, &handle_blktap_ctrlmsg, NULL, NULL);
+
+	/* Register handler to clean up when the domain is destroyed */
+	atexit(&shutdown_blktap);
+
+	return 0;
+}
diff -r 7530c4dba8a5 tools/ioemu/hw/xen_blktap.h
--- /dev/null	Mon Mar  3 15:19:39 2008
+++ b/tools/ioemu/hw/xen_blktap.h	Fri Mar 14 11:14:10 2008
@@ -0,0 +1,57 @@
+/* xen_blktap.h
+ *
+ * Generic disk interface for blktap-based image adapters.
+ *
+ * (c) 2006 Andrew Warfield and Julian Chesterfield
+ */
+
+#ifndef XEN_BLKTAP_H_ 
+#define XEN_BLKTAP_H_
+
+#include <stdint.h>
+#include <syslog.h>
+#include <stdio.h>
+
+#include "block_int.h"
+
+/* Things disks need to know about, these should probably be in a higher-level
+ * header. */
+#define MAX_SEGMENTS_PER_REQ    11
+#define SECTOR_SHIFT             9
+#define DEFAULT_SECTOR_SIZE    512
+
+#define MAX_IOFD                 2
+
+#define BLK_NOT_ALLOCATED       99
+#define TD_NO_PARENT             1
+
+typedef uint32_t td_flag_t;
+
+#define TD_RDONLY                1
+
+struct disk_id {
+	char *name;
+	int drivertype;
+};
+
+/* This structure represents the state of an active virtual disk.           */
+struct td_state {
+	BlockDriverState* bs;
+	td_flag_t flags;
+	void *blkif;
+	void *image;
+	void *ring_info;
+	void *fd_entry;
+	uint64_t sector_size;
+	uint64_t size;
+	unsigned int       info;
+};
+
+typedef struct fd_list_entry {
+	int cookie;
+	int  tap_fd;
+	struct td_state *s;
+	struct fd_list_entry **pprev, *next;
+} fd_list_entry_t;
+
+#endif /*XEN_BLKTAP_H_*/

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