From: Alan Huang <mmpgouride@gmail.com>
Date: Fri, 13 Jun 2025 13:19:50 +0000 (+0800)
Subject: bcachefs: Don't allocate new memory when mempool is exhausted
X-Git-Tag: v6.16-rc4~24^2~48
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9b9a3270092bf8030dbe21ce90b2d0c8d98d33c7;p=thirdparty%2Fkernel%2Flinux.git

bcachefs: Don't allocate new memory when mempool is exhausted

Allocating new memory when mempool is exhausted is too complicated, just
return ENOMEM is fine. memcpy is not needed, since there might be
pointers point to the old memory, that's the bug.

Signed-off-by: Alan Huang <mmpgouride@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index b586ecf2fdfa1..55de2e474705c 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -3217,28 +3217,8 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size, unsigned long
 	}
 
 	if (trans->used_mempool) {
-		if (trans->mem_bytes >= new_bytes)
-			goto out_change_top;
-
-		/* No more space from mempool item, need malloc new one */
-		new_mem = kmalloc(new_bytes, GFP_NOWAIT|__GFP_NOWARN);
-		if (unlikely(!new_mem)) {
-			bch2_trans_unlock(trans);
-
-			new_mem = kmalloc(new_bytes, GFP_KERNEL);
-			if (!new_mem)
-				return ERR_PTR(-BCH_ERR_ENOMEM_trans_kmalloc);
-
-			ret = bch2_trans_relock(trans);
-			if (ret) {
-				kfree(new_mem);
-				return ERR_PTR(ret);
-			}
-		}
-		memcpy(new_mem, trans->mem, trans->mem_top);
-		trans->used_mempool = false;
-		mempool_free(trans->mem, &c->btree_trans_mem_pool);
-		goto out_new_mem;
+		EBUG_ON(trans->mem_bytes >= new_bytes);
+		return ERR_PTR(-BCH_ERR_ENOMEM_trans_kmalloc);
 	}
 
 	new_mem = krealloc(trans->mem, new_bytes, GFP_NOWAIT|__GFP_NOWARN);
@@ -3249,7 +3229,6 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size, unsigned long
 		if (!new_mem && new_bytes <= BTREE_TRANS_MEM_MAX) {
 			new_mem = mempool_alloc(&c->btree_trans_mem_pool, GFP_KERNEL);
 			new_bytes = BTREE_TRANS_MEM_MAX;
-			memcpy(new_mem, trans->mem, trans->mem_top);
 			trans->used_mempool = true;
 			kfree(trans->mem);
 		}
@@ -3264,7 +3243,7 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size, unsigned long
 		if (ret)
 			return ERR_PTR(ret);
 	}
-out_new_mem:
+
 	trans->mem = new_mem;
 	trans->mem_bytes = new_bytes;
 
@@ -3273,7 +3252,7 @@ out_new_mem:
 		return ERR_PTR(btree_trans_restart_ip(trans,
 					BCH_ERR_transaction_restart_mem_realloced, _RET_IP_));
 	}
-out_change_top:
+
 	bch2_trans_kmalloc_trace(trans, size, ip);
 
 	p = trans->mem + trans->mem_top;