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SubjectRe: [PATCH] Posix file attribute support on VFAT
Bodo Eggert wrote:
> Hiroyuki Machida <machida@sm.sony.co.jp> wrote:
>
>
>>For newly created and/or modified files/dirs, system can utilize
>>full posix attributes, because memory resident inode storage can
>>hold those. After umount-mount cycle, system may lose some
>>attributes to preserve VFAT format.
>
>
> Inodes may be reclaimed, therefore you might also lose some attributes at
> runtime. For your users, that will look like a heisenbug. A similar bug
> has been reported for procfs. Is your implementation affected?

Yes.
Thank you, pointed it out. So I need to select
1) restric attribute even in mamory
or
2) pinn inode in memory during mount
(I think it's not good idea)

I'll revise the patch with 1).

>>- Special file
>> To distinguish special files, look if this fat dir entry
>> has ATTR_SYS, first. If it has ATTR_SYS, then check
>> 1st. LSB bit in ctime_cs, refered as "special file flag".
>> If set, this file is created under VFAT with "posix_attr".
>> Look up TYPE field to decide special file type.
>> This spcial file detection mothod has some flaw to make
>> potential confusion. E.g. some system file created under
>> dos/win may be treated as special file. However in most case,
>> user don't create system file under dos/win.
>
>
> You can add additional magic, e.g.: nodes must be empty, except for symlinks
> which must be not larger than 4KB (current PATH_MAX?). This will get rid
> of io.sys, logo.sys etc.\. If you want to be really sure, prepend a magic
> code to the on-disk representation of symlinks.

Please confirm my understanding.
You sugessted that symlink should not have ATTR_SYS, to prevent
some over 4KB files created in DOS/WIN to be treated as symlinks?

--
Hiroyuki Machida machida@sm.sony.co.jp
SSW Dept. HENC, Sony Corp.
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