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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 11-01-2010, 03:15 PM
Tejun Heo
 
Default block: reorganize claim/release implementation

With claim/release rolled into blkdev_get/put(), there's no reason to
keep bd_abort/finish_claim(), __bd_claim() and bd_release() as
separate functions. It only makes the code difficult to follow.
Collapse them into blkdev_get/put(). This will ease future changes
around claim/release.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
fs/block_dev.c | 127 +++++++++++++++++++++-----------------------------------
1 files changed, 48 insertions(+), 79 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index fc48912..269bfbb 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -772,79 +772,6 @@ static struct block_device *bd_start_claiming(struct block_device *bdev,
}
}

-/* releases bdev_lock */
-static void __bd_abort_claiming(struct block_device *whole, void *holder)
-{
- BUG_ON(whole->bd_claiming != holder);
- whole->bd_claiming = NULL;
- wake_up_bit(&whole->bd_claiming, 0);
-
- spin_unlock(&bdev_lock);
- bdput(whole);
-}
-
-/**
- * bd_abort_claiming - abort claiming a block device
- * @whole: whole block device returned by bd_start_claiming()
- * @holder: holder trying to claim @bdev
- *
- * Abort a claiming block started by bd_start_claiming(). Note that
- * @whole is not the block device to be claimed but the whole device
- * returned by bd_start_claiming().
- *
- * CONTEXT:
- * Grabs and releases bdev_lock.
- */
-static void bd_abort_claiming(struct block_device *whole, void *holder)
-{
- spin_lock(&bdev_lock);
- __bd_abort_claiming(whole, holder); /* releases bdev_lock */
-}
-
-/* increment holders when we have a legitimate claim. requires bdev_lock */
-static void __bd_claim(struct block_device *bdev, struct block_device *whole,
- void *holder)
-{
- /* note that for a whole device bd_holders
- * will be incremented twice, and bd_holder will
- * be set to bd_may_claim before being set to holder
- */
- whole->bd_holders++;
- whole->bd_holder = bd_may_claim;
- bdev->bd_holders++;
- bdev->bd_holder = holder;
-}
-
-/**
- * bd_finish_claiming - finish claiming a block device
- * @bdev: block device of interest (passed to bd_start_claiming())
- * @whole: whole block device returned by bd_start_claiming()
- * @holder: holder trying to claim @bdev
- *
- * Finish a claiming block started by bd_start_claiming().
- *
- * CONTEXT:
- * Grabs and releases bdev_lock.
- */
-static void bd_finish_claiming(struct block_device *bdev,
- struct block_device *whole, void *holder)
-{
- spin_lock(&bdev_lock);
- BUG_ON(!bd_may_claim(bdev, whole, holder));
- __bd_claim(bdev, whole, holder);
- __bd_abort_claiming(whole, holder); /* not actually an abort */
-}
-
-static void bd_release(struct block_device *bdev)
-{
- spin_lock(&bdev_lock);
- if (!--bdev->bd_contains->bd_holders)
- bdev->bd_contains->bd_holder = NULL;
- if (!--bdev->bd_holders)
- bdev->bd_holder = NULL;
- spin_unlock(&bdev_lock);
-}
-
#ifdef CONFIG_SYSFS
static int add_symlink(struct kobject *from, struct kobject *to)
{
@@ -1223,10 +1150,30 @@ int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
res = __blkdev_get(bdev, mode, 0);

if (whole) {
- if (res == 0)
- bd_finish_claiming(bdev, whole, holder);
- else
- bd_abort_claiming(whole, holder);
+ /* finish claiming */
+ spin_lock(&bdev_lock);
+
+ if (res == 0) {
+ BUG_ON(!bd_may_claim(bdev, whole, holder));
+ /*
+ * Note that for a whole device bd_holders
+ * will be incremented twice, and bd_holder
+ * will be set to bd_may_claim before being
+ * set to holder
+ */
+ whole->bd_holders++;
+ whole->bd_holder = bd_may_claim;
+ bdev->bd_holders++;
+ bdev->bd_holder = holder;
+ }
+
+ /* tell others that we're done */
+ BUG_ON(whole->bd_claiming != holder);
+ whole->bd_claiming = NULL;
+ wake_up_bit(&whole->bd_claiming, 0);
+
+ spin_unlock(&bdev_lock);
+ bdput(whole);
}

return res;
@@ -1272,6 +1219,7 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
bdev->bd_part_count--;

if (!--bdev->bd_openers) {
+ WARN_ON_ONCE(bdev->bd_holders);
sync_blockdev(bdev);
kill_bdev(bdev);
}
@@ -1303,10 +1251,31 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
int blkdev_put(struct block_device *bdev, fmode_t mode)
{
if (mode & FMODE_EXCL) {
+ bool bdev_free;
+
+ /*
+ * Release a claim on the device. The holder fields
+ * are protected with bdev_lock. bd_mutex is to
+ * synchronize disk_holder unlinking.
+ */
mutex_lock(&bdev->bd_mutex);
- bd_release(bdev);
- if (!bdev->bd_holders)
+ spin_lock(&bdev_lock);
+
+ WARN_ON_ONCE(--bdev->bd_holders < 0);
+ WARN_ON_ONCE(--bdev->bd_contains->bd_holders < 0);
+
+ /* bd_contains might point to self, check in a separate step */
+ if ((bdev_free = !bdev->bd_holders))
+ bdev->bd_holder = NULL;
+ if (!bdev->bd_contains->bd_holders)
+ bdev->bd_contains->bd_holder = NULL;
+
+ spin_unlock(&bdev_lock);
+
+ /* if this was the last claim, holder link should go too */
+ if (bdev_free)
bd_unlink_disk_holder(bdev);
+
mutex_unlock(&bdev->bd_mutex);
}
return __blkdev_put(bdev, mode, 0);
--
1.7.1

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