ubi: fastmap: Fix duplicate slab cache names while attaching

Since commit 4c39529 ("slab: Warn on duplicate cache names when
DEBUG_VM=y"), the duplicate slab cache names can be detected and a
kernel WARNING is thrown out.
In UBI fast attaching process, alloc_ai() could be invoked twice
with the same slab cache name 'ubi_aeb_slab_cache', which will trigger
following warning messages:
 kmem_cache of name 'ubi_aeb_slab_cache' already exists
 WARNING: CPU: 0 PID: 7519 at mm/slab_common.c:107
          __kmem_cache_create_args+0x100/0x5f0
 Modules linked in: ubi(+) nandsim [last unloaded: nandsim]
 CPU: 0 UID: 0 PID: 7519 Comm: modprobe Tainted: G 6.12.0-rc2
 RIP: 0010:__kmem_cache_create_args+0x100/0x5f0
 Call Trace:
   __kmem_cache_create_args+0x100/0x5f0
   alloc_ai+0x295/0x3f0 [ubi]
   ubi_attach+0x3c3/0xcc0 [ubi]
   ubi_attach_mtd_dev+0x17cf/0x3fa0 [ubi]
   ubi_init+0x3fb/0x800 [ubi]
   do_init_module+0x265/0x7d0
   __x64_sys_finit_module+0x7a/0xc0

The problem could be easily reproduced by loading UBI device by fastmap
with CONFIG_DEBUG_VM=y.
Fix it by using different slab names for alloc_ai() callers.

Fixes: d2158f6 ("UBI: Remove alloc_ai() slab name from parameter list")
Fixes: fdf10ed ("ubi: Rework Fastmap attach base code")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Author: Zhihao Cheng

drivers/mtd/ubi/attach.c

@@ -1447,7 +1447,7 @@ static int scan_all(struct ubi_device *ubi, struct ubi_attach_info *ai,
 	return err;
 }
 
-static struct ubi_attach_info *alloc_ai(void)
+static struct ubi_attach_info *alloc_ai(const char *slab_name)
 {
 	struct ubi_attach_info *ai;
 
@@ -1461,7 +1461,7 @@ static struct ubi_attach_info *alloc_ai(void)
 	INIT_LIST_HEAD(&ai->alien);
 	INIT_LIST_HEAD(&ai->fastmap);
 	ai->volumes = RB_ROOT;
-	ai->aeb_slab_cache = kmem_cache_create("ubi_aeb_slab_cache",
+	ai->aeb_slab_cache = kmem_cache_create(slab_name,
 					       sizeof(struct ubi_ainf_peb),
 					       0, 0, NULL);
 	if (!ai->aeb_slab_cache) {
@@ -1491,7 +1491,7 @@ static int scan_fast(struct ubi_device *ubi, struct ubi_attach_info **ai)
 
 	err = -ENOMEM;
 
-	scan_ai = alloc_ai();
+	scan_ai = alloc_ai("ubi_aeb_slab_cache_fastmap");
 	if (!scan_ai)
 		goto out;
 
@@ -1557,7 +1557,7 @@ int ubi_attach(struct ubi_device *ubi, int force_scan)
 	int err;
 	struct ubi_attach_info *ai;
 
-	ai = alloc_ai();
+	ai = alloc_ai("ubi_aeb_slab_cache");
 	if (!ai)
 		return -ENOMEM;
 
@@ -1575,7 +1575,7 @@ int ubi_attach(struct ubi_device *ubi, int force_scan)
 		if (err > 0 || mtd_is_eccerr(err)) {
 			if (err != UBI_NO_FASTMAP) {
 				destroy_ai(ai);
-				ai = alloc_ai();
+				ai = alloc_ai("ubi_aeb_slab_cache");
 				if (!ai)
 					return -ENOMEM;
 
@@ -1614,7 +1614,7 @@ int ubi_attach(struct ubi_device *ubi, int force_scan)
 	if (ubi->fm && ubi_dbg_chk_fastmap(ubi)) {
 		struct ubi_attach_info *scan_ai;
 
-		scan_ai = alloc_ai();
+		scan_ai = alloc_ai("ubi_aeb_slab_cache_dbg_chk_fastmap");
 		if (!scan_ai) {
 			err = -ENOMEM;
 			goto out_wl;