[Toybox] Stat, wrong blockcount for F2FS filesystems?

enh enh at google.com
Fri Apr 7 18:55:36 PDT 2017


yeah, there was a stat bug that was fixed. some filesystems modify the
block value before passing it back. drosen fixed sdcardfs to look at this
in "ANDROID: sdcardfs: Get the blocksize from the lower fs":

int f2fs_getattr(struct vfsmount *mnt,
struct dentry *dentry, struct kstat *stat)
{
struct inode *inode = dentry->d_inode;
generic_fillattr(inode, stat);
stat->blocks <<= 3;
return 0;
}

so that's where the factor of 8 would come from.


On Fri, Apr 7, 2017 at 11:31 AM, darken <darken at darken.eu> wrote:

> Wrong train of thought, toybox stat doesn't do any blockcount calculation,
> but just gets the value from `st_blocks`.
>
> We are getting bad values from `/storage/emulated/0` which is FUSE mounted
> from `/data/media/0` and the blockcount values from `/data/media/0` are
> sane.
>
> So this seems to be FUSE related...
>
> ~Matthias
>
> 2017-04-07 18:10 GMT+02:00 darken <darken at darken.eu>:
>
>> I'm using stat to display filesize and allocated size in my Android app.
>>
>> I calculate the allocated size by multiplying the block count (%b) with
>> 512 Byte.
>>
>> I found out in https://github.com/landley/toybox/issues/41 that the
>> blocksize for the blockcount calculation is hardcoded to 512. So this
>> should work well (and has so far).
>>
>> Now a user of my app noticed that on their F2FS filesystem the allocated
>> size is suspiciously small:
>> https://github.com/d4rken/sdmaid-public/issues/830
>>
>> Specifically too small by a factor of 8, as if the blocksize used for
>> blockcount calculation is 4096 (4096/512).
>>
>> Could stat have a problem with calculating the blockcount on F2FS
>> filesystems or am I overlooking something else?
>>
>> ~Matthias
>>
>
>
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>


-- 
Elliott Hughes - http://who/enh - http://jessies.org/~enh/
Android native code/tools questions? Mail me/drop by/add me as a reviewer.
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