Re: [PATCH] erofs: set SB_NODEV sb_flags when mounting with fsid

[Baokun Li <libaokun1@huawei.com>]

On 2024/4/16 22:49, Gao Xiang wrote:
> On Tue, Apr 16, 2024 at 02:35:08PM +0200, Christian Brauner wrote:
>>>> I'm not sure how to resolve it in EROFS itself, anyway...
>> Instead of allocating the erofs_sb_info in fill_super() allocate it
>> during erofs_get_tree() and then you can ensure that you always have the
>> info you need available during erofs_kill_sb(). See the appended
>> (untested) patch.
> Hi Christian,
>
> Yeah, that is a good way I think.  Although sbi will be allocated
> unconditionally instead but that is minor.
>
> I'm on OSSNA this week, will test this patch more when returning.
>
> Hi Baokun,
>
> Could you also check this on your side?
>
> Thanks,
> Gao Xiang
Hi Xiang,

This patch does fix the initial problem.


Hi Christian,

Thanks for the patch, this is a good idea. Just with nits below.
Otherwise feel free to add.

Reviewed-and-tested-by: Baokun Li <libaokun1@huawei.com>
>
>>  From e4f586a41748b6edc05aca36d49b7b39e55def81 Mon Sep 17 00:00:00 2001
>> From: Christian Brauner <brauner@kernel.org>
>> Date: Mon, 15 Apr 2024 20:17:46 +0800
>> Subject: [PATCH] erofs: reliably distinguish block based and fscache mode
>>
SNIP

>>
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index c0eb139adb07..4ed80154edf8 100644
>> --- a/fs/erofs/super.c
>> +++ b/fs/erofs/super.c
>> @@ -581,7 +581,7 @@ static const struct export_operations erofs_export_ops = {
>>   static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>   {
>>   	struct inode *inode;
>> -	struct erofs_sb_info *sbi;
>> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>>   	struct erofs_fs_context *ctx = fc->fs_private;
>>   	int err;
>>   
>> @@ -590,15 +590,10 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>   	sb->s_maxbytes = MAX_LFS_FILESIZE;
>>   	sb->s_op = &erofs_sops;
>>   
>> -	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>> -	if (!sbi)
>> -		return -ENOMEM;
>> -
>>   	sb->s_fs_info = sbi;
This line is no longer needed.
>>   	sbi->opt = ctx->opt;
>>   	sbi->devs = ctx->devs;
>>   	ctx->devs = NULL;
>> -	sbi->fsid = ctx->fsid;
>>   	ctx->fsid = NULL;
>>   	sbi->domain_id = ctx->domain_id;
>>   	ctx->domain_id = NULL;
Since erofs_sb_info is now allocated in erofs_fc_get_tree(), why not
encapsulate the above lines as erofs_ctx_to_info() helper function
to be called in erofs_fc_get_tree()？Then erofs_fc_fill_super() wouldn't
have to use erofs_fs_context and would prevent the fsid from being
freed twice.
>> @@ -707,8 +702,15 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>   static int erofs_fc_get_tree(struct fs_context *fc)
>>   {
>>   	struct erofs_fs_context *ctx = fc->fs_private;
>> +	struct erofs_sb_info *sbi;
>> +
>> +	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>> +	if (!sbi)
>> +		return -ENOMEM;
>>   
>> -	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->fsid)
>> +	fc->s_fs_info = sbi;
>> +	sbi->fsid = ctx->fsid;
Here ctx->fsid is not set to null, so fsid may be freed twice.
>> +	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
>>   		return get_tree_nodev(fc, erofs_fc_fill_super);
>>   
>>   	return get_tree_bdev(fc, erofs_fc_fill_super);
>> @@ -762,11 +764,15 @@ static void erofs_free_dev_context(struct erofs_dev_context *devs)
>>   static void erofs_fc_free(struct fs_context *fc)
>>   {
>>   	struct erofs_fs_context *ctx = fc->fs_private;
>> +	struct erofs_sb_info *sbi = fc->s_fs_info;
>>   
>>   	erofs_free_dev_context(ctx->devs);
>>   	kfree(ctx->fsid);
>>   	kfree(ctx->domain_id);
>>   	kfree(ctx);
>> +
>> +	if (sbi)
>> +		kfree(sbi);
There's no need to check sbi, kfree does.
>>   }
>>   
>>   static const struct fs_context_operations erofs_context_ops = {
>> @@ -783,6 +789,7 @@ static int erofs_init_fs_context(struct fs_context *fc)
>>   	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
>>   	if (!ctx)
>>   		return -ENOMEM;
>> +
>>   	ctx->devs = kzalloc(sizeof(struct erofs_dev_context), GFP_KERNEL);
>>   	if (!ctx->devs) {
>>   		kfree(ctx);
>> @@ -799,17 +806,13 @@ static int erofs_init_fs_context(struct fs_context *fc)
>>   
>>   static void erofs_kill_sb(struct super_block *sb)
>>   {
>> -	struct erofs_sb_info *sbi;
>> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>>   
>> -	if (erofs_is_fscache_mode(sb))
>> +	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
>>   		kill_anon_super(sb);
>>   	else
>>   		kill_block_super(sb);
>>   
>> -	sbi = EROFS_SB(sb);
>> -	if (!sbi)
>> -		return;
>> -
>>   	erofs_free_dev_context(sbi->devs);
>>   	fs_put_dax(sbi->dax_dev, NULL);
>>   	erofs_fscache_unregister_fs(sb);
>> -- 
>> 2.43.0
>>