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Next: [PATCH 10/16] blkfront: Clean up vbd release
From: Jeremy Fitzhardinge on 20 Jul 2010 16:50
From: Jan Beulich <jbeulich(a)novell.com>

Prevent prematurely freeing 'struct blkfront_info' instances (when the
xenbus data structures are gone, but the Linux ones are still needed).

Prevent adding a disk with the same (major, minor) [and hence the same
name and sysfs entries, which leads to oopses] when the previous
instance wasn't fully de-allocated yet.

This still doesn't address all issues resulting from forced detach:
I/O submitted after the detach still blocks forever, likely preventing
subsequent un-mounting from completing. It's not clear to me (not
knowing much about the block layer) how this can be avoided.

Signed-off-by: Jan Beulich <jbeulich(a)novell.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge(a)citrix.com>
---
drivers/block/xen-blkfront.c | 83 +++++++++++++++++++++++++++++++++++++++---
1 files changed, 78 insertions(+), 5 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 6839947..b1b16e5 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -104,6 +104,10 @@ struct blkfront_info

static DEFINE_SPINLOCK(blkif_io_lock);

+static unsigned int nr_minors;
+static unsigned long *minors;
+static DEFINE_SPINLOCK(minor_lock);
+
#define MAXIMUM_OUTSTANDING_BLOCK_REQS \
(BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
#define GRANT_INVALID_REF 0
@@ -138,6 +142,55 @@ static void add_id_to_freelist(struct blkfront_info *info,
info->shadow_free = id;
}

+static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
+{
+ unsigned int end = minor + nr;
+ int rc;
+
+ if (end > nr_minors) {
+ unsigned long *bitmap, *old;
+
+ bitmap = kzalloc(BITS_TO_LONGS(end) * sizeof(*bitmap),
+ GFP_KERNEL);
+ if (bitmap == NULL)
+ return -ENOMEM;
+
+ spin_lock(&minor_lock);
+ if (end > nr_minors) {
+ old = minors;
+ memcpy(bitmap, minors,
+ BITS_TO_LONGS(nr_minors) * sizeof(*bitmap));
+ minors = bitmap;
+ nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;
+ } else
+ old = bitmap;
+ spin_unlock(&minor_lock);
+ kfree(old);
+ }
+
+ spin_lock(&minor_lock);
+ if (find_next_bit(minors, end, minor) >= end) {
+ for (; minor < end; ++minor)
+ __set_bit(minor, minors);
+ rc = 0;
+ } else
+ rc = -EBUSY;
+ spin_unlock(&minor_lock);
+
+ return rc;
+}
+
+static void xlbd_release_minors(unsigned int minor, unsigned int nr)
+{
+ unsigned int end = minor + nr;
+
+ BUG_ON(end > nr_minors);
+ spin_lock(&minor_lock);
+ for (; minor < end; ++minor)
+ __clear_bit(minor, minors);
+ spin_unlock(&minor_lock);
+}
+
static void blkif_restart_queue_callback(void *arg)
{
struct blkfront_info *info = (struct blkfront_info *)arg;
@@ -417,9 +470,14 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
if ((minor % nr_parts) == 0)
nr_minors = nr_parts;

+ err = xlbd_reserve_minors(minor, nr_minors);
+ if (err)
+ goto out;
+ err = -ENODEV;
+
gd = alloc_disk(nr_minors);
if (gd == NULL)
- goto out;
+ goto release;

offset = minor / nr_parts;

@@ -450,7 +508,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,

if (xlvbd_init_blk_queue(gd, sector_size)) {
del_gendisk(gd);
- goto out;
+ goto release;
}

info->rq = gd->queue;
@@ -470,6 +528,8 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,

return 0;

+ release:
+ xlbd_release_minors(minor, nr_minors);
out:
return err;
}
@@ -924,6 +984,7 @@ static void blkfront_connect(struct blkfront_info *info)
static void blkfront_closing(struct xenbus_device *dev)
{
struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+ unsigned int minor, nr_minors;
unsigned long flags;

dev_dbg(&dev->dev, "blkfront_closing: %s removed\n", dev->nodename);
@@ -946,7 +1007,10 @@ static void blkfront_closing(struct xenbus_device *dev)
blk_cleanup_queue(info->rq);
info->rq = NULL;

+ minor = info->gd->first_minor;
+ nr_minors = info->gd->minors;
del_gendisk(info->gd);
+ xlbd_release_minors(minor, nr_minors);

out:
xenbus_frontend_closed(dev);
@@ -1004,7 +1068,10 @@ static int blkfront_remove(struct xenbus_device *dev)

blkif_free(info, 0);

- kfree(info);
+ if(info->users == 0)
+ kfree(info);
+ else
+ info->is_ready = -1;

return 0;
}
@@ -1013,12 +1080,15 @@ static int blkfront_is_ready(struct xenbus_device *dev)
{
struct blkfront_info *info = dev_get_drvdata(&dev->dev);

- return info->is_ready;
+ return info->is_ready > 0;
}

static int blkif_open(struct block_device *bdev, fmode_t mode)
{
struct blkfront_info *info = bdev->bd_disk->private_data;
+
+ if(info->is_ready < 0)
+ return -ENODEV;
info->users++;
return 0;
}
@@ -1034,7 +1104,10 @@ static int blkif_release(struct gendisk *disk, fmode_t mode)
struct xenbus_device *dev = info->xbdev;
enum xenbus_state state = xenbus_read_driver_state(dev->otherend);

- if (state == XenbusStateClosing && info->is_ready)
+ if(info->is_ready < 0) {
+ blkfront_closing(dev);
+ kfree(info);
+ } else if (state == XenbusStateClosing && info->is_ready)
blkfront_closing(dev);
}
return 0;
--
1.7.1.1

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Prev: [PATCH 07/16] xenbus: Make xenbus_switch_state transactional
Next: [PATCH 10/16] blkfront: Clean up vbd release