[patch 054/135] dcache: allocate external names from reclaimable kmalloc caches

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From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: dcache: allocate external names from reclaimable kmalloc caches

We can use the newly introduced kmalloc-reclaimable-X caches, to allocate
external names in dcache, which will take care of the proper accounting
automatically, and also improve anti-fragmentation page grouping.

This effectively reverts commit f1782c9bc547 ("dcache: account external
names as indirectly reclaimable memory") and instead passes
__GFP_RECLAIMABLE to kmalloc().  The accounting thus moves from
NR_INDIRECTLY_RECLAIMABLE_BYTES to NR_SLAB_RECLAIMABLE, which is also
considered in MemAvailable calculation and overcommit decisions.

Link: http://lkml.kernel.org/r/20180731090649.16028-4-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/dcache.c |   38 +++++++++-----------------------------
 1 file changed, 9 insertions(+), 29 deletions(-)

--- a/fs/dcache.c~dcache-allocate-external-names-from-reclaimable-kmalloc-caches
+++ a/fs/dcache.c
@@ -257,24 +257,10 @@ static void __d_free(struct rcu_head *he
 	kmem_cache_free(dentry_cache, dentry); 
 }
 
-static void __d_free_external_name(struct rcu_head *head)
-{
-	struct external_name *name = container_of(head, struct external_name,
-						  u.head);
-
-	mod_node_page_state(page_pgdat(virt_to_page(name)),
-			    NR_INDIRECTLY_RECLAIMABLE_BYTES,
-			    -ksize(name));
-
-	kfree(name);
-}
-
 static void __d_free_external(struct rcu_head *head)
 {
 	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
-
-	__d_free_external_name(&external_name(dentry)->u.head);
-
+	kfree(external_name(dentry));
 	kmem_cache_free(dentry_cache, dentry);
 }
 
@@ -306,7 +292,7 @@ void release_dentry_name_snapshot(struct
 		struct external_name *p;
 		p = container_of(name->name, struct external_name, name[0]);
 		if (unlikely(atomic_dec_and_test(&p->u.count)))
-			call_rcu(&p->u.head, __d_free_external_name);
+			kfree_rcu(p, u.head);
 	}
 }
 EXPORT_SYMBOL(release_dentry_name_snapshot);
@@ -1606,7 +1592,6 @@ EXPORT_SYMBOL(d_invalidate);
  
 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 {
-	struct external_name *ext = NULL;
 	struct dentry *dentry;
 	char *dname;
 	int err;
@@ -1627,14 +1612,15 @@ struct dentry *__d_alloc(struct super_bl
 		dname = dentry->d_iname;
 	} else if (name->len > DNAME_INLINE_LEN-1) {
 		size_t size = offsetof(struct external_name, name[1]);
-
-		ext = kmalloc(size + name->len, GFP_KERNEL_ACCOUNT);
-		if (!ext) {
+		struct external_name *p = kmalloc(size + name->len,
+						  GFP_KERNEL_ACCOUNT |
+						  __GFP_RECLAIMABLE);
+		if (!p) {
 			kmem_cache_free(dentry_cache, dentry); 
 			return NULL;
 		}
-		atomic_set(&ext->u.count, 1);
-		dname = ext->name;
+		atomic_set(&p->u.count, 1);
+		dname = p->name;
 	} else  {
 		dname = dentry->d_iname;
 	}	
@@ -1673,12 +1659,6 @@ struct dentry *__d_alloc(struct super_bl
 		}
 	}
 
-	if (unlikely(ext)) {
-		pg_data_t *pgdat = page_pgdat(virt_to_page(ext));
-		mod_node_page_state(pgdat, NR_INDIRECTLY_RECLAIMABLE_BYTES,
-				    ksize(ext));
-	}
-
 	this_cpu_inc(nr_dentry);
 
 	return dentry;
@@ -2707,7 +2687,7 @@ static void copy_name(struct dentry *den
 		dentry->d_name.hash_len = target->d_name.hash_len;
 	}
 	if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
-		call_rcu(&old_name->u.head, __d_free_external_name);
+		kfree_rcu(old_name, u.head);
 }
 
 /*
_



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