2023-07-07 11:27 GMT+09:00, gaoming <gaoming20@xxxxxxxxxxx>:
> exfat_get_dentry_set could be called after the u-disk have been inserted,
> through exfat_find, __exfat_write_inode functions.
> This could happen at any time, which scenario can not guarantee the
> continuity of physical memory.
> This bugfix will enhance the robustness of exfat.
I'm sorry, but I understood that it was changed even though you didn't
find any particular problem. I think there will not be issues like
allocation-bitmap allocation failures. I will delete this code and
apply it. If you don't agree, please explain how much memory is
allocated here.
Thanks.
>
> Thanks.
> -----邮件原件-----
> 发件人: Namjae Jeon <linkinjeon@xxxxxxxxxx>
> 发送时间: 2023年7月7日 7:10
> 收件人: gaoming <gaoming20@xxxxxxxxxxx>
> 抄送: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>; open list:EXFAT FILE SYSTEM
> <linux-fsdevel@xxxxxxxxxxxxxxx>; open list <linux-kernel@xxxxxxxxxxxxxxx>;
> fengbaopeng <fengbaopeng@xxxxxxxxxxx>; gaoxu <gaoxu2@xxxxxxxxxxx>; wangfei
> 00014658 <wangfei66@xxxxxxxxxxx>; shenchen 00013118
> <harry.shen@xxxxxxxxxxx>
> 主题: Re: [PATCH] exfat: use kvmalloc_array/kvfree instead of
> kmalloc_array/kfree
>
> 2023-07-05 18:15 GMT+09:00, gaoming <gaoming20@xxxxxxxxxxx>:
>> 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@xxxxxxxxxxx>
>> ---
>> 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);
> Could you please elaborate why you change this to kvmalloc_array also?
>
> Thanks.
>> if (!es->bh) {
>> brelse(bh);
>> return -ENOMEM;
>> --
>> 2.17.1
>>
>>
>
