On Oct 14, 2012, at 12:52 AM, Arnd Bergmann wrote:

> On Friday 05 October 2012, 김재극 wrote:
>> +const char *media_ext_lists[] = {
>> +       "jpg",
>> +       "gif",
>> +       "png",
>> +       "avi",
>> +       "divx",
>> +       "mp4",
>> +       "mp3",
>> ...
> 
>> + * Set multimedia files as cold files for hot/cold data separation
>> + */
>> +static inline void set_cold_file(struct inode *inode, const unsigned char 
>> *name)
>> +{
>> +       const char **extlist = media_ext_lists;
>> +
>> +       while (*extlist) {
>> +               if (!is_multimedia_file(name, *extlist)) {
>> +                       F2FS_I(inode)->is_cold = 1;
>> +                       break;
>> +               }
>> +               extlist++;
>> +       }
>> +}
> 
> This is a very clever way of categorizing files by their name, but I wonder 
> if hardcoding
> the list of file name extensions at in the kernel source is the best 
> strategy. Generally
> I would consider this to be a policy that should be configurable by the user.
> 

I think that file extensions can't be a steady basis for categorization. It is 
possible that user can use any extension as you want during file naming (for 
example, save text file with png extension). Or it is possible to use file 
without any extension. Only magics in a file structure can be a steady basis. 
But analyzing of file structure on the file system driver level is a breaking 
of some fundamentals, from my point of view.

With the best regards,
Vyacheslav Dubeyko.

> Unfortunately I can't think of a good interface to configure this, but maybe 
> someone
> else has a useful idea. Maybe the list can be stored in the superblock and 
> get written
> at mkfs time from the same defaults, but with the option of overriding it 
> using
> a debugfs tool.
> 
>       Arnd
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