erofs: use struct lockref to replace handcrafted approach

Let's avoid the current handcrafted lockref although `struct lockref`
inclusion usually increases extra 4 bytes with an explicit spinlock if
CONFIG_DEBUG_SPINLOCK is off.

Apart from the size difference, note that the meaning of refcount is
also changed to active users. IOWs, it doesn't take an extra refcount
for XArray tree insertion.

I don't observe any significant performance difference at least on
our cloud compute server but the new one indeed simplifies the
overall codebase a bit.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Link: https://lore.kernel.org/r/20230529123727.79943-1-hsiangkao@linux.alibaba.com

1 files changed, 2 insertions, 36 deletions

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 005f3391bcd3..36e32fa542f0 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -208,46 +208,12 @@ enum {
 	EROFS_ZIP_CACHE_READAROUND
 };
 
-#define EROFS_LOCKED_MAGIC     (INT_MIN | 0xE0F510CCL)
-
 /* basic unit of the workstation of a super_block */
 struct erofs_workgroup {
-	/* the workgroup index in the workstation */
 	pgoff_t index;
-
-	/* overall workgroup reference count */
-	atomic_t refcount;
+	struct lockref lockref;
 };
 
-static inline bool erofs_workgroup_try_to_freeze(struct erofs_workgroup *grp,
-						 int val)
-{
-	preempt_disable();
-	if (val != atomic_cmpxchg(&grp->refcount, val, EROFS_LOCKED_MAGIC)) {
-		preempt_enable();
-		return false;
-	}
-	return true;
-}
-
-static inline void erofs_workgroup_unfreeze(struct erofs_workgroup *grp,
-					    int orig_val)
-{
-	/*
-	 * other observers should notice all modifications
-	 * in the freezing period.
-	 */
-	smp_mb();
-	atomic_set(&grp->refcount, orig_val);
-	preempt_enable();
-}
-
-static inline int erofs_wait_on_workgroup_freezed(struct erofs_workgroup *grp)
-{
-	return atomic_cond_read_relaxed(&grp->refcount,
-					VAL != EROFS_LOCKED_MAGIC);
-}
-
 enum erofs_kmap_type {
 	EROFS_NO_KMAP,		/* don't map the buffer */
 	EROFS_KMAP,		/* use kmap_local_page() to map the buffer */
@@ -486,7 +452,7 @@ static inline void erofs_pagepool_add(struct page **pagepool, struct page *page)
 void erofs_release_pages(struct page **pagepool);
 
 #ifdef CONFIG_EROFS_FS_ZIP
-int erofs_workgroup_put(struct erofs_workgroup *grp);
+void erofs_workgroup_put(struct erofs_workgroup *grp);
 struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
 					     pgoff_t index);
 struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,