在 2018年4月1日，下午3:11，Amir Goldstein <amir73il@xxxxxxxxx> 写道：
>
> On Sun, Apr 1, 2018 at 7:57 AM, Chengguang Xu <cgxu519@xxxxxxx> wrote:
>> Some overlayfs mount options cannot be changed via remount,
>> but remount operation does not return proper error even if
>> we specify different value to unchangeable options.
>>
>> This patch add option parsing support for remount so we can
>> recogonize unchangeable options in remount.
>>
>> Signed-off-by: Chengguang Xu <cgxu519@xxxxxxx>
>> ---
>> fs/overlayfs/super.c | 19 +++++++++++++------
>> 1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>> index 7c24619..5c8944b 100644
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -446,14 +446,10 @@ static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
>> return 0;
>> }
>>
>> -static int ovl_parse_opt(char *opt, struct ovl_config *config)
>> +static int ovl_parse_opt(char *opt, struct ovl_config *config, bool remount)
>> {
>> char *p;
>>
>> - config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
>> - if (!config->redirect_mode)
>> - return -ENOMEM;
>> -
>> while ((p = ovl_next_opt(&opt)) != NULL) {
>> int token;
>> substring_t args[MAX_OPT_ARGS];
>> @@ -517,6 +513,9 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
>> }
>> }
>>
>> + if (remount)
>> + return 0;
>> +
>> /* Workdir is useless in non-upper mount */
>> if (!config->upperdir && config->workdir) {
>> pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
>> @@ -525,6 +524,13 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
>> config->workdir = NULL;
>> }
>>
>> + if (!config->redirect_mode) {
>> + config->redirect_mode = kstrdup(ovl_redirect_mode_def(),
>> + GFP_KERNEL);
>> + if (!config->redirect_mode)
>> + return -ENOMEM;
>> + }
>> +
>
> You can move this chunk into ovl_parse_redirect_mode() no?
I just guess the purpose of sending "config->redirect_mode” as function parameter,
then I think the author hopes adding ‘const’ attribution to the string when doing
comparison. I’m not so sure should break the rule or not, What do you think?
>
>> return ovl_parse_redirect_mode(config, config->redirect_mode);
>> }
>>
>> @@ -1250,6 +1256,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>> struct ovl_entry *oe;
>> struct ovl_fs *ofs;
>> struct cred *cred;
>> + bool remount = false;
>
> This helper var is not needed.
>
> Thanks,
> Amir.
>
>> int err;
>>
>> err = -ENOMEM;
>> @@ -1263,7 +1270,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>>
>> ofs->config.index = ovl_index_def;
>> ofs->config.nfs_export = ovl_nfs_export_def;
>> - err = ovl_parse_opt((char *) data, &ofs->config);
>> + err = ovl_parse_opt((char *) data, &ofs->config, remount);
>> if (err)
>> goto out_err;
>>
>> --
>> 1.8.3.1
>>
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