fs: cosmetic fixes to lru handling

1. inode_bit_waitqueue() was somehow placed between __inode_add_lru() and
   inode_add_lru(). move it up
2. assert ->i_lock is held in __inode_add_lru instead of just claiming it is
   needed
3. s/__inode_add_lru/__inode_lru_list_add/ for consistency with itself
   (inode_lru_list_del()) and similar routines for sb and io list
   management
4. push list presence check into inode_lru_list_del(), just like sb and
   io list

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20251029131428.654761-2-mjguzik@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/fs-writeback.c

@@ -1452,7 +1452,7 @@ static void inode_sync_complete(struct inode *inode)
 
 	inode_state_clear(inode, I_SYNC);
 	/* If inode is clean an unused, put it into LRU now... */
-	inode_add_lru(inode);
+	inode_lru_list_add(inode);
 	/* Called with inode->i_lock which ensures memory ordering. */
 	inode_wake_up_bit(inode, __I_SYNC);
 }

fs/inode.c

@@ -530,23 +530,6 @@ void ihold(struct inode *inode)
 }
 EXPORT_SYMBOL(ihold);
 
-static void __inode_add_lru(struct inode *inode, bool rotate)
-{
-	if (inode_state_read(inode) & (I_DIRTY_ALL | I_SYNC | I_FREEING | I_WILL_FREE))
-		return;
-	if (icount_read(inode))
-		return;
-	if (!(inode->i_sb->s_flags & SB_ACTIVE))
-		return;
-	if (!mapping_shrinkable(&inode->i_data))
-		return;
-
-	if (list_lru_add_obj(&inode->i_sb->s_inode_lru, &inode->i_lru))
-		this_cpu_inc(nr_unused);
-	else if (rotate)
-		inode_state_set(inode, I_REFERENCED);
-}
-
 struct wait_queue_head *inode_bit_waitqueue(struct wait_bit_queue_entry *wqe,
 					    struct inode *inode, u32 bit)
 {
@@ -584,18 +567,38 @@ void wait_on_new_inode(struct inode *inode)
 }
 EXPORT_SYMBOL(wait_on_new_inode);
 
+static void __inode_lru_list_add(struct inode *inode, bool rotate)
+{
+	lockdep_assert_held(&inode->i_lock);
+
+	if (inode_state_read(inode) & (I_DIRTY_ALL | I_SYNC | I_FREEING | I_WILL_FREE))
+		return;
+	if (icount_read(inode))
+		return;
+	if (!(inode->i_sb->s_flags & SB_ACTIVE))
+		return;
+	if (!mapping_shrinkable(&inode->i_data))
+		return;
+
+	if (list_lru_add_obj(&inode->i_sb->s_inode_lru, &inode->i_lru))
+		this_cpu_inc(nr_unused);
+	else if (rotate)
+		inode_state_set(inode, I_REFERENCED);
+}
+
 /*
  * Add inode to LRU if needed (inode is unused and clean).
- *
- * Needs inode->i_lock held.
  */
-void inode_add_lru(struct inode *inode)
+void inode_lru_list_add(struct inode *inode)
 {
-	__inode_add_lru(inode, false);
+	__inode_lru_list_add(inode, false);
 }
 
 static void inode_lru_list_del(struct inode *inode)
 {
+	if (list_empty(&inode->i_lru))
+		return;
+
 	if (list_lru_del_obj(&inode->i_sb->s_inode_lru, &inode->i_lru))
 		this_cpu_dec(nr_unused);
 }
@@ -1920,7 +1923,7 @@ static void iput_final(struct inode *inode)
 	if (!drop &&
 	    !(inode_state_read(inode) & I_DONTCACHE) &&
 	    (sb->s_flags & SB_ACTIVE)) {
-		__inode_add_lru(inode, true);
+		__inode_lru_list_add(inode, true);
 		spin_unlock(&inode->i_lock);
 		return;
 	}
@@ -1944,8 +1947,7 @@ static void iput_final(struct inode *inode)
 		inode_state_replace(inode, I_WILL_FREE, I_FREEING);
 	}
 
-	if (!list_empty(&inode->i_lru))
+	inode_lru_list_del(inode);
-		inode_lru_list_del(inode);
 	spin_unlock(&inode->i_lock);
 
 	evict(inode);

include/linux/fs.h

@@ -3502,7 +3502,7 @@ static inline void remove_inode_hash(struct inode *inode)
 }
 
 extern void inode_sb_list_add(struct inode *inode);
-extern void inode_add_lru(struct inode *inode);
+extern void inode_lru_list_add(struct inode *inode);
 
 extern int sb_set_blocksize(struct super_block *, int);
 extern int sb_min_blocksize(struct super_block *, int);

mm/filemap.c

@@ -256,7 +256,7 @@ void filemap_remove_folio(struct folio *folio)
 	__filemap_remove_folio(folio, NULL);
 	xa_unlock_irq(&mapping->i_pages);
 	if (mapping_shrinkable(mapping))
-		inode_add_lru(mapping->host);
+		inode_lru_list_add(mapping->host);
 	spin_unlock(&mapping->host->i_lock);
 
 	filemap_free_folio(mapping, folio);
@@ -335,7 +335,7 @@ void delete_from_page_cache_batch(struct address_space *mapping,
 	page_cache_delete_batch(mapping, fbatch);
 	xa_unlock_irq(&mapping->i_pages);
 	if (mapping_shrinkable(mapping))
-		inode_add_lru(mapping->host);
+		inode_lru_list_add(mapping->host);
 	spin_unlock(&mapping->host->i_lock);
 
 	for (i = 0; i < folio_batch_count(fbatch); i++)

mm/truncate.c

@@ -46,7 +46,7 @@ static void clear_shadow_entries(struct address_space *mapping,
 
 	xas_unlock_irq(&xas);
 	if (mapping_shrinkable(mapping))
-		inode_add_lru(mapping->host);
+		inode_lru_list_add(mapping->host);
 	spin_unlock(&mapping->host->i_lock);
 }
 
@@ -111,7 +111,7 @@ static void truncate_folio_batch_exceptionals(struct address_space *mapping,
 
 	xas_unlock_irq(&xas);
 	if (mapping_shrinkable(mapping))
-		inode_add_lru(mapping->host);
+		inode_lru_list_add(mapping->host);
 	spin_unlock(&mapping->host->i_lock);
 out:
 	folio_batch_remove_exceptionals(fbatch);
@@ -622,7 +622,7 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
 	__filemap_remove_folio(folio, NULL);
 	xa_unlock_irq(&mapping->i_pages);
 	if (mapping_shrinkable(mapping))
-		inode_add_lru(mapping->host);
+		inode_lru_list_add(mapping->host);
 	spin_unlock(&mapping->host->i_lock);
 
 	filemap_free_folio(mapping, folio);

mm/vmscan.c

@@ -811,7 +811,7 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
 		__filemap_remove_folio(folio, shadow);
 		xa_unlock_irq(&mapping->i_pages);
 		if (mapping_shrinkable(mapping))
-			inode_add_lru(mapping->host);
+			inode_lru_list_add(mapping->host);
 		spin_unlock(&mapping->host->i_lock);
 
 		if (free_folio)

mm/workingset.c

@@ -755,7 +755,7 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
 	xa_unlock_irq(&mapping->i_pages);
 	if (mapping->host != NULL) {
 		if (mapping_shrinkable(mapping))
-			inode_add_lru(mapping->host);
+			inode_lru_list_add(mapping->host);
 		spin_unlock(&mapping->host->i_lock);
 	}
 	ret = LRU_REMOVED_RETRY;