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>

1 files changed, 48 insertions, 79 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index fc48912354d1..269bfbbd10fc 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);