[PATCH 4/9] block: turn bdev_lock into a mutex

Christoph Hellwig
2023-05-05T17:53:08Z

There is no reason for this lock to spin, and being able to sleep under
it will come in handy soon.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/bdev.c | 27 +++++++++++++--------------
1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index f2c7181b0bba7d..bad75f6cf8edcd 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -308,7 +308,7 @@ EXPORT_SYMBOL(thaw_bdev);
* pseudo-fs
*/

-static __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);
+static __cacheline_aligned_in_smp DEFINE_MUTEX(bdev_lock);
static struct kmem_cache * bdev_cachep __read_mostly;

static struct inode *bdev_alloc_inode(struct super_block *sb)
@@ -457,15 +457,14 @@ long nr_blockdev_pages(void)
*
* Test whether @bdev can be claimed by @holder.
*
- * CONTEXT:
- * spin_lock(&bdev_lock).
- *
* RETURNS:
* %true if @bdev can be claimed, %false otherwise.
*/
static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
void *holder)
{
+ lockdep_assert_held(&bdev_lock);
+
if (bdev->bd_holder == holder)
return true; /* already a holder */
else if (bdev->bd_holder != NULL)
@@ -500,10 +499,10 @@ int bd_prepare_to_claim(struct block_device *bdev, void *holder)
if (WARN_ON_ONCE(!holder))
return -EINVAL;
retry:
- spin_lock(&bdev_lock);
+ mutex_lock(&bdev_lock);
/* if someone else claimed, fail */
if (!bd_may_claim(bdev, whole, holder)) {
- spin_unlock(&bdev_lock);
+ mutex_unlock(&bdev_lock);
return -EBUSY;
}

@@ -513,7 +512,7 @@ int bd_prepare_to_claim(struct block_device *bdev, void *holder)
DEFINE_WAIT(wait);

prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
- spin_unlock(&bdev_lock);
+ mutex_unlock(&bdev_lock);
schedule();
finish_wait(wq, &wait);
goto retry;
@@ -521,7 +520,7 @@ int bd_prepare_to_claim(struct block_device *bdev, void *holder)

/* yay, all mine */
whole->bd_claiming = holder;
- spin_unlock(&bdev_lock);
+ mutex_unlock(&bdev_lock);
return 0;
}
EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */
@@ -547,7 +546,7 @@ static void bd_finish_claiming(struct block_device *bdev, void *holder)
{
struct block_device *whole = bdev_whole(bdev);

- spin_lock(&bdev_lock);
+ mutex_lock(&bdev_lock);
BUG_ON(!bd_may_claim(bdev, whole, holder));
/*
* Note that for a whole device bd_holders will be incremented twice,
@@ -558,7 +557,7 @@ static void bd_finish_claiming(struct block_device *bdev, void *holder)
bdev->bd_holders++;
bdev->bd_holder = holder;
bd_clear_claiming(whole, holder);
- spin_unlock(&bdev_lock);
+ mutex_unlock(&bdev_lock);
}

/**
@@ -572,9 +571,9 @@ static void bd_finish_claiming(struct block_device *bdev, void *holder)
*/
void bd_abort_claiming(struct block_device *bdev, void *holder)
{
- spin_lock(&bdev_lock);
+ mutex_lock(&bdev_lock);
bd_clear_claiming(bdev_whole(bdev), holder);
- spin_unlock(&bdev_lock);
+ mutex_unlock(&bdev_lock);
}
EXPORT_SYMBOL(bd_abort_claiming);

@@ -587,7 +586,7 @@ static void bd_end_claim(struct block_device *bdev)
* Release a claim on the device. The holder fields are protected with
* bdev_lock. open_mutex is used to synchronize disk_holder unlinking.
*/
- spin_lock(&bdev_lock);
+ mutex_lock(&bdev_lock);
WARN_ON_ONCE(--bdev->bd_holders < 0);
WARN_ON_ONCE(--whole->bd_holders < 0);
if (!bdev->bd_holders) {
@@ -597,7 +596,7 @@ static void bd_end_claim(struct block_device *bdev)
}
if (!whole->bd_holders)
whole->bd_holder = NULL;
- spin_unlock(&bdev_lock);
+ mutex_unlock(&bdev_lock);

/*
* If this was the last claim, remove holder link and unblock evpoll if
--
2.39.2