Some follow-up:
The issue only occurs with "bigalloc" enabled.
echo 3 > /proc/sys/vm/drop_caches
seems to detach the blocked disk space from the files (so that 'du file' no longer includes the offset), but it does not free the space, 'df' still shows all file overheads as used disk space.
Am 02.11.2017 um 20:17 schrieb mfe555:
Hi, I'm using ext4 on a Linux based Enigma2 set-top box, kernel 4.8.3.
When creating a fresh file, there is a significant difference in file
size (ls -la) and disk usage (du). When making two copies of the file ..
gbquad:/hdd/test# cp file file.copy1
gbquad:/hdd/test# cp file file.copy2
gbquad:/hdd/test# ls -la
-rw------- 1 root root 581821460 Nov 1 18:52 file
-rw------- 1 root root 581821460 Nov 1 18:56 file.copy1
-rw------- 1 root root 581821460 Nov 1 18:57 file.copy2
gbquad:/hdd/test# du *
607232 file
658176 file.copy1
644864 file.copy2
... all three files show an overhead in the ~10% range, and the
overhead is different for these files although their md5sums are equal.
When deleting a file (rm), the overhead remains occupied on the disk.
For example, after deleting "file", "df" reports approx. 581821460
more bytes free, not 607232 kbytes more free space. The overhead
(607232 kB - 581821460 B =pprox. 39 MB) remains blocked.
When re-booting, the blocked space becomes free again, and in addition
the overhead of those files that were not deleted also disappears, so
that after a reboot the'file size' and 'disk usage' match for all
files (except for rounding up to some block size).
A colleague and I have observed this on two different "kernel 4.8.3"
boxes and three ext4 disks, but not on a "kernel 3.14" box also using
ext4.
Can anyone help me with this ?
Thanks a lot
Lukas
