This patch allocates the blktap devices on demand. I used my previous
patch as a starting point (but this patch is still against
xen-unstable). The previous patch had the tapfds in a link list, but
Andrew and I have agreed that the O(n) search is not efficient.
This patch keeps the array, and allocates 256 pointers. But the
pointers are now what is allocated on demand.
-- Steve
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
diff -r f0302ed1ac62 linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c
--- a/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c Mon Oct 02 11:47:55
2006 -0400
+++ b/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c Mon Oct 02 17:37:01
2006 -0400
@@ -9,6 +9,9 @@
* Based on the blkback driver code.
*
* Copyright (c) 2004-2005, Andrew Warfield and Julian Chesterfield
+ *
+ * Clean ups and fix ups:
+ * Copyright (c) 2006, Steven Rostedt - Red Hat, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
@@ -51,7 +54,7 @@
#include <asm/tlbflush.h>
#include <linux/devfs_fs_kernel.h>
-#define MAX_TAP_DEV 100 /*the maximum number of tapdisk ring devices */
+#define MAX_TAP_DEV 256 /*the maximum number of tapdisk ring devices */
#define MAX_DEV_NAME 100 /*the max tapdisk ring device name e.g. blktap0 */
@@ -104,6 +107,12 @@ static int mmap_pages = MMAP_PAGES;
* have a bunch of pages reserved for shared
* memory rings.
*/
+
+/*Data struct handed back to userspace for tapdisk device to VBD mapping*/
+typedef struct domid_translate {
+ unsigned short domid;
+ unsigned short busid;
+} domid_translate_t ;
/*Data struct associated with each of the tapdisk devices*/
typedef struct tap_blkif {
@@ -123,17 +132,11 @@ typedef struct tap_blkif {
unsigned long *idx_map; /*Record the user ring id to kern
[req id, idx] tuple */
blkif_t *blkif; /*Associate blkif with tapdev */
- int sysfs_set; /*Set if it has a class device. */
+ struct domid_translate trans; /*Translation from domid to bus. */
} tap_blkif_t;
-/*Data struct handed back to userspace for tapdisk device to VBD mapping*/
-typedef struct domid_translate {
- unsigned short domid;
- unsigned short busid;
-} domid_translate_t ;
-
-static domid_translate_t translate_domid[MAX_TAP_DEV];
-static tap_blkif_t *tapfds[MAX_TAP_DEV];
+static struct tap_blkif *tapfds[MAX_TAP_DEV];
+static int blktap_next_minor;
static int __init set_blkif_reqs(char *str)
{
@@ -320,7 +323,7 @@ struct vm_operations_struct blktap_vm_op
*/
/*Function Declarations*/
-static int get_next_free_dev(void);
+static tap_blkif_t *get_next_free_dev(void);
static int blktap_open(struct inode *inode, struct file *filp);
static int blktap_release(struct inode *inode, struct file *filp);
static int blktap_mmap(struct file *filp, struct vm_area_struct *vma);
@@ -338,51 +341,94 @@ static struct file_operations blktap_fop
};
-static int get_next_free_dev(void)
+static tap_blkif_t *get_next_free_dev(void)
{
tap_blkif_t *info;
- int i = 0, ret = -1;
- unsigned long flags;
-
- spin_lock_irqsave(&pending_free_lock, flags);
-
- while (i < MAX_TAP_DEV) {
+ int minor;
+
+ /*
+ * This is called only from the ioctl, which
+ * means we should always have interrupts enabled.
+ */
+ BUG_ON(irqs_disabled());
+
+ spin_lock_irq(&pending_free_lock);
+
+ for (minor = 1; minor < blktap_next_minor; minor++) {
+ info = tapfds[minor];
+ /* we could have failed a previous attempt. */
+ if (!info ||
+ ((info->dev_inuse == 0) &&
+ (info->dev_pending == 0)) ) {
+ info->dev_pending = 1;
+ goto found;
+ }
+ }
+ info = NULL;
+ minor = -1;
+
+ /*
+ * We didn't find free device. If we can still allocate
+ * more, then we grab the next device minor that is
+ * available. This is done while we are still under
+ * the protection of the pending_free_lock.
+ */
+ if (blktap_next_minor < MAX_TAP_DEV)
+ minor = blktap_next_minor++;
+found:
+ spin_unlock_irq(&pending_free_lock);
+
+ if (!info && minor > 0) {
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (unlikely(!info)) {
+ /*
+ * If we failed here, try to put back
+ * the next minor number. But if one
+ * was just taken, then we just lose this
+ * minor. We can try to allocate this
+ * minor again later.
+ */
+ spin_lock_irq(&pending_free_lock);
+ if (blktap_next_minor == minor+1)
+ blktap_next_minor--;
+ spin_unlock_irq(&pending_free_lock);
+ goto out;
+ }
+
+ info->minor = minor;
+ /*
+ * Make sure that we have a minor before others can
+ * see us.
+ */
+ wmb();
+ tapfds[minor] = info;
+
+ class_device_create(xen_class, NULL,
+ MKDEV(blktap_major, minor), NULL,
+ "blktap%d", minor);
+ devfs_mk_cdev(MKDEV(blktap_major, minor),
+ S_IFCHR|S_IRUGO|S_IWUSR, "xen/blktap%d", minor);
+ }
+
+out:
+ return info;
+}
+
+int dom_to_devid(domid_t domid, int xenbus_id, blkif_t *blkif)
+{
+ tap_blkif_t *info;
+ int i;
+
+ for (i = 0; i < blktap_next_minor; i++) {
info = tapfds[i];
- if ( (tapfds[i] != NULL) && (info->dev_inuse == 0)
- && (info->dev_pending == 0) ) {
- info->dev_pending = 1;
- ret = i;
- goto done;
- }
- i++;
- }
-
-done:
- spin_unlock_irqrestore(&pending_free_lock, flags);
-
- /*
- * We are protected by having the dev_pending set.
- */
- if (!tapfds[i]->sysfs_set && xen_class) {
- class_device_create(xen_class, NULL,
- MKDEV(blktap_major, ret), NULL,
- "blktap%d", ret);
- tapfds[i]->sysfs_set = 1;
- }
- return ret;
-}
-
-int dom_to_devid(domid_t domid, int xenbus_id, blkif_t *blkif)
-{
- int i;
-
- for (i = 0; i < MAX_TAP_DEV; i++)
- if ( (translate_domid[i].domid == domid)
- && (translate_domid[i].busid == xenbus_id) ) {
- tapfds[i]->blkif = blkif;
- tapfds[i]->status = RUNNING;
+ if ( info &&
+ (info->trans.domid == domid) &&
+ (info->trans.busid == xenbus_id) ) {
+ info->blkif = blkif;
+ info->status = RUNNING;
return i;
}
+ }
return -1;
}
@@ -392,12 +438,16 @@ void signal_tapdisk(int idx)
struct task_struct *ptask;
info = tapfds[idx];
- if ( (idx > 0) && (idx < MAX_TAP_DEV) && (info->pid > 0) ) {
+ if ((idx < 0) || (idx > MAX_TAP_DEV) || !info)
+ return;
+
+ if (info->pid > 0) {
ptask = find_task_by_pid(info->pid);
if (ptask)
info->status = CLEANSHUTDOWN;
}
info->blkif = NULL;
+
return;
}
@@ -408,14 +458,15 @@ static int blktap_open(struct inode *ino
tap_blkif_t *info;
int i;
- if (tapfds[idx] == NULL) {
+ info = tapfds[idx];
+
+ if ((idx < 0) || (idx > MAX_TAP_DEV) || !info) {
WPRINTK("Unable to open device /dev/xen/blktap%d\n",
- idx);
- return -ENOMEM;
- }
+ idx);
+ return -ENODEV;
+ }
+
DPRINTK("Opening device /dev/xen/blktap%d\n",idx);
-
- info = tapfds[idx];
/*Only one process can access device at a time*/
if (test_and_set_bit(0, &info->dev_inuse))
@@ -617,33 +668,31 @@ static int blktap_ioctl(struct inode *in
{
uint64_t val = (uint64_t)arg;
domid_translate_t *tr = (domid_translate_t *)&val;
- int newdev;
DPRINTK("NEWINTF Req for domid %d and bus id %d\n",
tr->domid, tr->busid);
- newdev = get_next_free_dev();
- if (newdev < 1) {
+ info = get_next_free_dev();
+ if (!info) {
WPRINTK("Error initialising /dev/xen/blktap - "
"No more devices\n");
return -1;
}
- translate_domid[newdev].domid = tr->domid;
- translate_domid[newdev].busid = tr->busid;
- return newdev;
+ info->trans.domid = tr->domid;
+ info->trans.busid = tr->busid;
+ return info->minor;
}
case BLKTAP_IOCTL_FREEINTF:
{
unsigned long dev = arg;
unsigned long flags;
- /* Looking at another device */
- info = NULL;
-
- if ( (dev > 0) && (dev < MAX_TAP_DEV) )
- info = tapfds[dev];
+ info = tapfds[dev];
+
+ if ((dev > MAX_TAP_DEV) || !info)
+ return 0; /* should this be an error? */
spin_lock_irqsave(&pending_free_lock, flags);
- if ( (info != NULL) && (info->dev_pending) )
+ if (info->dev_pending)
info->dev_pending = 0;
spin_unlock_irqrestore(&pending_free_lock, flags);
@@ -653,16 +702,12 @@ static int blktap_ioctl(struct inode *in
{
unsigned long dev = arg;
- /* Looking at another device */
- info = NULL;
-
- if ( (dev > 0) && (dev < MAX_TAP_DEV) )
- info = tapfds[dev];
-
- if (info != NULL)
- return info->minor;
- else
- return -1;
+ info = tapfds[dev];
+
+ if (!dev || (dev > MAX_TAP_DEV) || !info)
+ return -EINVAL;
+
+ return info->minor;
}
case BLKTAP_IOCTL_MAJOR:
return blktap_major;
@@ -702,13 +747,13 @@ void blktap_kick_user(int idx)
{
tap_blkif_t *info;
- if (idx == 0)
+ info = tapfds[idx];
+
+ /* Don't kick control device minor==0 */
+ if ((idx <= 0) || (idx > MAX_TAP_DEV) || !info)
return;
-
- info = tapfds[idx];
-
- if (info != NULL)
- wake_up_interruptible(&info->wait);
+
+ wake_up_interruptible(&info->wait);
return;
}
@@ -868,8 +913,8 @@ static void free_req(pending_req_t *req)
wake_up(&pending_free_wq);
}
-static void fast_flush_area(pending_req_t *req, int k_idx, int u_idx, int
- tapidx)
+static void fast_flush_area(pending_req_t *req, int k_idx, int u_idx,
+ int tapidx)
{
struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST*2];
unsigned int i, invcount = 0;
@@ -877,13 +922,16 @@ static void fast_flush_area(pending_req_
uint64_t ptep;
int ret, mmap_idx;
unsigned long kvaddr, uvaddr;
-
- tap_blkif_t *info = tapfds[tapidx];
-
- if (info == NULL) {
+ tap_blkif_t *info;
+
+
+ info = tapfds[tapidx];
+
+ if ((tapidx < 0) || (tapidx > MAX_TAP_DEV) || !info) {
WPRINTK("fast_flush: Couldn't get info!\n");
return;
}
+
mmap_idx = req->mem_idx;
for (i = 0; i < req->nr_pages; i++) {
@@ -1088,7 +1136,7 @@ static int do_block_io_op(blkif_t *blkif
rmb(); /* Ensure we see queued requests up to 'rp'. */
/*Check blkif has corresponding UE ring*/
- if (blkif->dev_num == -1) {
+ if (blkif->dev_num < 0) {
/*oops*/
if (print_dbug) {
WPRINTK("Corresponding UE "
@@ -1099,7 +1147,8 @@ static int do_block_io_op(blkif_t *blkif
}
info = tapfds[blkif->dev_num];
- if (info == NULL || !info->dev_inuse) {
+
+ if (blkif->dev_num > MAX_TAP_DEV || !info || !info->dev_inuse) {
if (print_dbug) {
WPRINTK("Can't get UE info!\n");
print_dbug = 0;
@@ -1167,16 +1216,24 @@ static void dispatch_rw_block_io(blkif_t
struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST*2];
unsigned int nseg;
int ret, i;
- tap_blkif_t *info = tapfds[blkif->dev_num];
+ tap_blkif_t *info;
uint64_t sector;
blkif_request_t *target;
int pending_idx = RTN_PEND_IDX(pending_req,pending_req->mem_idx);
- int usr_idx = GET_NEXT_REQ(info->idx_map);
+ int usr_idx;
uint16_t mmap_idx = pending_req->mem_idx;
+ info = tapfds[blkif->dev_num];
+
+ if (blkif->dev_num < 0 || blkif->dev_num > MAX_TAP_DEV || !info)
+ goto fail_response;
+
+ usr_idx = GET_NEXT_REQ(info->idx_map);
+
/*Check we have space on user ring - should never fail*/
- if(usr_idx == INVALID_REQ) goto fail_flush;
+ if (usr_idx == INVALID_REQ)
+ goto fail_flush;
/* Check that number of segments is sane. */
nseg = req->nr_segments;
@@ -1390,9 +1447,6 @@ static int __init blkif_init(void)
tap_blkif_xenbus_init();
- /*Create the blktap devices, but do not map memory or waitqueue*/
- for(i = 0; i < MAX_TAP_DEV; i++) translate_domid[i].domid = 0xFFFF;
-
/* Dynamically allocate a major for this device */
ret = register_chrdev(0, "blktap", &blktap_fops);
blktap_dir = devfs_mk_dir(NULL, "xen", 0, NULL);
@@ -1404,24 +1458,22 @@ static int __init blkif_init(void)
blktap_major = ret;
- for(i = 0; i < MAX_TAP_DEV; i++ ) {
- info = tapfds[i] = kzalloc(sizeof(tap_blkif_t),GFP_KERNEL);
- if(tapfds[i] == NULL)
- return -ENOMEM;
- info->minor = i;
- info->pid = 0;
- info->blkif = NULL;
-
- ret = devfs_mk_cdev(MKDEV(blktap_major, i),
- S_IFCHR|S_IRUGO|S_IWUSR, "xen/blktap%d", i);
-
- if(ret != 0)
- return -ENOMEM;
- info->dev_pending = info->dev_inuse = 0;
-
- DPRINTK("Created misc_dev [/dev/xen/blktap%d]\n",i);
- }
-
+ info = kzalloc(sizeof(tap_blkif_t),GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+
+ blktap_next_minor++;
+
+ ret = devfs_mk_cdev(MKDEV(blktap_major, i),
+ S_IFCHR|S_IRUGO|S_IWUSR, "xen/blktap%d", i);
+
+ if(ret != 0)
+ return -ENOMEM;
+
+ DPRINTK("Created misc_dev [/dev/xen/blktap%d]\n",i);
+
+ tapfds[0] = info;
+
/* Make sure the xen class exists */
if (!setup_xen_class()) {
/*
@@ -1434,7 +1486,6 @@ static int __init blkif_init(void)
class_device_create(xen_class, NULL,
MKDEV(blktap_major, 0), NULL,
"blktap0");
- tapfds[0]->sysfs_set = 1;
} else {
/* this is bad, but not fatal */
WPRINTK("blktap: sysfs xen_class not created\n");
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