ext4: factor out __es_alloc_extent() and __es_free_extent()

Factor out __es_alloc_extent() and __es_free_extent(), which only allocate
and free extent_status in these two helpers.

The ext4_es_alloc_extent() function is split into __es_alloc_extent()
and ext4_es_init_extent(). In __es_alloc_extent() we allocate memory using
GFP_KERNEL | __GFP_NOFAIL | __GFP_ZERO if the memory allocation cannot
fail, otherwise we use GFP_ATOMIC. and the ext4_es_init_extent() is used to
initialize extent_status and update related variables after a successful
allocation.

This is to prepare for the use of pre-allocated extent_status later.
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230424033846.4732-4-libaokun1@huawei.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents_status.c

@@ -459,14 +459,17 @@ static inline bool ext4_es_must_keep(struct extent_status *es)
 	return false;
 }
 
-static struct extent_status *
-ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
-		     ext4_fsblk_t pblk)
+static inline struct extent_status *__es_alloc_extent(bool nofail)
+{
+	if (!nofail)
+		return kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);
+
+	return kmem_cache_zalloc(ext4_es_cachep, GFP_KERNEL | __GFP_NOFAIL);
+}
+
+static void ext4_es_init_extent(struct inode *inode, struct extent_status *es,
+		ext4_lblk_t lblk, ext4_lblk_t len, ext4_fsblk_t pblk)
 {
-	struct extent_status *es;
-	es = kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);
-	if (es == NULL)
-		return NULL;
 	es->es_lblk = lblk;
 	es->es_len = len;
 	es->es_pblk = pblk;
@@ -481,8 +484,11 @@ ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
 
 	EXT4_I(inode)->i_es_all_nr++;
 	percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
+}
 
-	return es;
+static inline void __es_free_extent(struct extent_status *es)
+{
+	kmem_cache_free(ext4_es_cachep, es);
 }
 
 static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
@@ -499,7 +505,7 @@ static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
 					s_es_stats.es_stats_shk_cnt);
 	}
 
-	kmem_cache_free(ext4_es_cachep, es);
+	__es_free_extent(es);
 }
 
 /*
@@ -800,10 +806,12 @@ static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
 		}
 	}
 
-	es = ext4_es_alloc_extent(inode, newes->es_lblk, newes->es_len,
-				  newes->es_pblk);
+	es = __es_alloc_extent(false);
 	if (!es)
 		return -ENOMEM;
+	ext4_es_init_extent(inode, es, newes->es_lblk, newes->es_len,
+			    newes->es_pblk);
+
 	rb_link_node(&es->rb_node, parent, p);
 	rb_insert_color(&es->rb_node, &tree->root);