linux-kernel - [PATCH] exfat: use kvmalloc_array/kvfree instead of kmalloc

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Date:   Wed, 5 Jul 2023 09:15:52 +0000
From:   gaoming <gaoming20@...onor.com>
To:     Namjae Jeon <linkinjeon@...nel.org>,
        Sungjong Seo <sj1557.seo@...sung.com>
CC:     "open list:EXFAT FILE SYSTEM" <linux-fsdevel@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        fengbaopeng <fengbaopeng@...onor.com>,
        gaoxu <gaoxu2@...onor.com>,
        wangfei 00014658 <wangfei66@...onor.com>,
        "shenchen 00013118" <harry.shen@...onor.com>
Subject: [PATCH] exfat: use kvmalloc_array/kvfree instead of
 kmalloc_array/kfree

The call stack shown below is a scenario in the Linux 4.19 kernel.
Allocating memory failed where exfat fs use kmalloc_array due 
to system memory fragmentation, while the u-disk was inserted
without recognition.
Devices such as u-disk using the exfat file system are pluggable and may be
insert into the system at any time.
However, long-term running systems cannot guarantee the continuity of 
physical memory. Therefore, it's necessary to address this issue.

Binder:2632_6: page allocation failure: order:4,
mode:0x6040c0(GFP_KERNEL|__GFP_COMP), nodemask=(null)
Call trace:
[242178.097582]  dump_backtrace+0x0/0x4
[242178.097589]  dump_stack+0xf4/0x134
[242178.097598]  warn_alloc+0xd8/0x144
[242178.097603]  __alloc_pages_nodemask+0x1364/0x1384
[242178.097608]  kmalloc_order+0x2c/0x510
[242178.097612]  kmalloc_order_trace+0x40/0x16c
[242178.097618]  __kmalloc+0x360/0x408
[242178.097624]  load_alloc_bitmap+0x160/0x284
[242178.097628]  exfat_fill_super+0xa3c/0xe7c
[242178.097635]  mount_bdev+0x2e8/0x3a0
[242178.097638]  exfat_fs_mount+0x40/0x50
[242178.097643]  mount_fs+0x138/0x2e8
[242178.097649]  vfs_kern_mount+0x90/0x270
[242178.097655]  do_mount+0x798/0x173c
[242178.097659]  ksys_mount+0x114/0x1ac
[242178.097665]  __arm64_sys_mount+0x24/0x34
[242178.097671]  el0_svc_common+0xb8/0x1b8
[242178.097676]  el0_svc_handler+0x74/0x90
[242178.097681]  el0_svc+0x8/0x340

By analyzing the exfat code,we found that continuous physical memory is
not required here,so kvmalloc_array is used can solve this problem.

Signed-off-by: gaoming <gaoming20@...onor.com>
---
 fs/exfat/balloc.c | 4 ++--
 fs/exfat/dir.c    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c
index 9f42f25fab92..a183558cb7a0 100644
--- a/fs/exfat/balloc.c
+++ b/fs/exfat/balloc.c
@@ -69,7 +69,7 @@ static int exfat_allocate_bitmap(struct super_block *sb,
 	}
 	sbi->map_sectors = ((need_map_size - 1) >>
 			(sb->s_blocksize_bits)) + 1;
-	sbi->vol_amap = kmalloc_array(sbi->map_sectors,
+	sbi->vol_amap = kvmalloc_array(sbi->map_sectors,
 				sizeof(struct buffer_head *), GFP_KERNEL);
 	if (!sbi->vol_amap)
 		return -ENOMEM;
@@ -84,7 +84,7 @@ static int exfat_allocate_bitmap(struct super_block *sb,
 			while (j < i)
 				brelse(sbi->vol_amap[j++]);
 
-			kfree(sbi->vol_amap);
+			kvfree(sbi->vol_amap);
 			sbi->vol_amap = NULL;
 			return -EIO;
 		}
diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 957574180a5e..5cbb78d0a2a2 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -649,7 +649,7 @@ int exfat_put_dentry_set(struct exfat_entry_set_cache *es, int sync)
 			brelse(es->bh[i]);
 
 	if (IS_DYNAMIC_ES(es))
-		kfree(es->bh);
+		kvfree(es->bh);
 
 	return err;
 }
@@ -888,7 +888,7 @@ int exfat_get_dentry_set(struct exfat_entry_set_cache *es,
 
 	num_bh = EXFAT_B_TO_BLK_ROUND_UP(off + num_entries * DENTRY_SIZE, sb);
 	if (num_bh > ARRAY_SIZE(es->__bh)) {
-		es->bh = kmalloc_array(num_bh, sizeof(*es->bh), GFP_KERNEL);
+		es->bh = kvmalloc_array(num_bh, sizeof(*es->bh), GFP_KERNEL);
 		if (!es->bh) {
 			brelse(bh);
 			return -ENOMEM;
-- 
2.17.1