Signed-off-by: NAdrian Hunter <adrian.hunter@nokia.com>

This patch cleans up write-buffer timeout initialization and
sets it to 3-5 interval.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch adds the following minor optimization:

1. If write-buffer does not use the timer, indicate it with the
   wbuf->no_timer variable, instead of using the wbuf->softlimit
   variable. This is better because wbuf->softlimit is of ktime_t
   type, and the ktime_to_ns function contains 64-bit multiplication.

2. Do not call the 'hrtimer_cancel()' function for write-buffers
   which do not use timers.

3. Do not cancel the timer in 'ubifs_put_super()' because the
   synchronization function does this.

This patch also removes a confusing comment.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBIFS uses timers for write-buffer write-back. It is not
crucial for us to write-back exactly on time. We are fine
to write-back a little earlier or later. And this means
we may optimize UBIFS timer so that it could be groped
with a close timer event, so that the CPU would not be
waken up just to do the write back. This is optimization
to lessen power consumption, which is important in
embedded devices UBIFS is used for.

hrtimers have a nice feature: they are effectively range
timers, and we may defind the soft and hard limits for
it. Standard timers do not have these feature. They may
only be made deferrable, but this means there is effectively
no hard limit. So, we will better use hrtimers.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Now UBIFS is supported by u-boot. If we ever decide to change the
media format, then people will have to upgrade their u-boots to
mount new format images. However, very often it is possible to
preserve R/O forward-compatibility, even though the write
forward-compatibility is not preserved.

This patch introduces a new super-block field which stores the
R/O compatibility version.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: NAdrian Hunter <Adrian.Hunter@nokia.com>

This patch introduces a helpful @c->idx_leb_size variable.
The patch also fixes some spelling issues and makes comments
use "LEB" instead of "eraseblock", which is more correct.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Make 'ubifs_find_free_space()' return offset where free space starts,
rather than the amount of free space. This is just more appropriat
for its caller.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This UBIFS feature has never worked properly, and it was a mistake
to add it because we simply have no use-cases. So, lets still accept
the fast_unmount mount option, but ignore it. This does not change
much, because UBIFS commit in sync_fs anyway, and sync_fs is called
while unmounting.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

- preserve the idx_gc list - it will be needed in the same
state, should UBIFS be remounted rw again
- prevent remounting ro if we have switched to read only
mode (due to a fatal error)
Signed-off-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When data CRC checking is disabled, UBIFS returns incorrect return
code from the 'try_read_node()' function (0 instead of 1, which means
CRC error), which make the caller re-read the data node again, but using
a different code patch, so the second read is fine. Thus, we read the
same node twice. And the result of this is that UBIFS is slower
with no_chk_data_crc option than it is with chk_data_crc option.
This patches fixes the problem.
Reported-by: NReuben Dowle <Reuben.Dowle@navico.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When mounting read-only the orphan area head is
not initialized.  It must be initialized when
remounting read/write, but it was not.  This patch
fixes that.

[Artem: sorry, added comment tweaking noise]
Signed-off-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

We observe space corrupted accounting when re-mounting. So add some
debbugging checks to catch problems like this.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

When freeing the c->idx_lebs list, we have to release the LEBs as well,
because we might be called from mount to read-only mode code. Otherwise
the LEBs stay taken forever, which may cause problems when we re-mount
back ro RW mode.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Just add more commentaries. Also some commentary fixes for
lprops flags.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Mark super, file, and inode operation structcutes with 'const'.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

These are mostly long lines and wrong indentation warning
fixes. But also there are two volatile variables and
checkpatch.pl complains about them:

WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
+       volatile int gc_seq;

WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
+       volatile int gced_lnum;

Well, we anyway use smp_wmb() for c->gc_seq and c->gced_lnum, so
these 'volatile' modifiers can be just dropped.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Instead of using do_div(), use better primitives from
linux/math64.h.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Take into account that 2 eraseblocks are never available because
they are reserved for the index. This gives more realistic count
of FS blocks.

To avoid future confusions like this, introduce a constant.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Dump available space calculated by budgeting subsystem.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch fixes the following section mismatch:

WARNING: fs/ubifs/ubifs.o(.init.text+0xec): Section mismatch in reference from the function init_module() to the function .exit.text:ubifs_compressors_exit()
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

We need to have a possibility to see various UBIFS variables
and ask UBIFS to dump various information. Debugfs is what
we need.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Introduce a new data structure which contains all debugging
stuff inside. This is cleaner than having debugging stuff
directly in 'c'.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

It is very handy to be able to change default UBIFS compressor
via mount options. Introduce -o compr=<name> mount option support.
Currently only "none", "lzo" and "zlib" compressors are supported.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Save a 4 bytes of RAM per 'struct inode' by stroring inode
compression type in bit-filed, instead of using 'int'.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

To avoid memory allocation failure during bulk-read, pre-allocate
a bulk-read buffer, so that if there is only one bulk-reader at
a time, it would just use the pre-allocated buffer and would not
do any memory allocation. However, if there are more than 1 bulk-
reader, then only one reader would use the pre-allocated buffer,
while the other reader would allocate the buffer for itself.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Bulk-read allocates 128KiB or more using kmalloc. The allocation
starts failing often when the memory gets fragmented. UBIFS still
works fine in this case, because it falls-back to standard
(non-optimized) read method, though. This patch teaches bulk-read
to allocate exactly the amount of memory it needs, instead of
allocating 128KiB every time.

This patch is also a preparation to the further fix where we'll
have a pre-allocated bulk-read buffer as well. For example, now
the @bu object is prepared in 'ubifs_bulk_read()', so we could
path either pre-allocated or allocated information to
'ubifs_do_bulk_read()' later. Or teaching 'ubifs_do_bulk_read()'
not to allocate 'bu->buf' if it is already there.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Bulk-read allocates a lot of memory with 'kmalloc()', and when it
is/gets fragmented 'kmalloc()' fails with a scarry warning. But
because bulk-read is just an optimization, UBIFS keeps working fine.
Supress the warning by passing __GFP_NOWARN option to 'kmalloc()'.

This patch also introduces a macro for the magic 128KiB constant.
This is just neater.

Note, this is not really fixes the problem we had, but just hides
the warnings. The further patches fix the problem.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Also add debugging checks for LPT size and separate
out c->check_lpt_free from unrelated bitfields.
Signed-off-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>

Znode may refer both data nodes and indexing nodes
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

We cannot store bit-fields together if the processes which
change them may race, unless we serialize them.

Thus, move the nospc and nospc_rp bit-fields eway from
the mount option/constant bit-fields, to avoid races.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

The "bulk_read" and "no_chk_data_crc" have only 2 values -
0 and 1. We already have bit-fields in corresponding data
structers, so make "bulk_read" and "no_chk_data_crc"
bit-fields as well.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBIFS read performance can be improved by skipping the CRC
check when data nodes are read.  This option can be used if
the underlying media is considered to be highly reliable.
Note that CRCs are always checked for metadata.

Read speed on Arm platform with OneNAND goes from 19 MiB/s
to 27 MiB/s with data CRC checking disabled.
Signed-off-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>

Some flash media are capable of reading sequentially at faster rates.
UBIFS bulk-read facility is designed to take advantage of that, by
reading in one go consecutive data nodes that are also located
consecutively in the same LEB.

Read speed on Arm platform with OneNAND goes from 17 MiB/s to
19 MiB/s.
Signed-off-by: NAdrian Hunter <ext-adrian.hunter@nokia.com>

'ubifs_get_lprops()' and 'ubifs_release_lprops()' basically wrap
mutex lock and unlock. We have them because we want lprops subsystem
be separate and as independent as possible. And we planned better
locking rules for lprops.

Anyway, because they are short, it is better to inline them.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Since free space we report in statfs is file size which should
fit to the FS - change the way we calculate free space and use
leb_overhead instead of dark_wm in calculations.

Results of "freespace" test (120MiB volume, 16KiB LEB size,
512 bytes page size). Before the change:

freespace: Test 1: fill the space we have 3 times
freespace: was free: 85204992 bytes 81.3 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 11284480 bytes 10.8 MiB, wrote 13.2% more than predicted
freespace: was free: 83554304 bytes 79.7 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 12935168 bytes 12.3 MiB, wrote 15.5% more than predicted
freespace: was free: 83554304 bytes 79.7 MiB, wrote: 96493568 bytes 92.0 MiB, delta: 12939264 bytes 12.3 MiB, wrote 15.5% more than predicted
freespace: Test 1 finished

freespace: Test 2: gradually lessen amount of free space and fill the FS
freespace: do 10 steps, lessen free space by 7596218 bytes 7.2 MiB each time
freespace: was free: 78675968 bytes 75.0 MiB, wrote: 88903680 bytes 84.8 MiB, delta: 10227712 bytes 9.8 MiB, wrote 13.0% more than predicted
freespace: was free: 72015872 bytes 68.7 MiB, wrote: 81514496 bytes 77.7 MiB, delta: 9498624 bytes 9.1 MiB, wrote 13.2% more than predicted
freespace: was free: 63938560 bytes 61.0 MiB, wrote: 72589312 bytes 69.2 MiB, delta: 8650752 bytes 8.2 MiB, wrote 13.5% more than predicted
freespace: was free: 56127488 bytes 53.5 MiB, wrote: 63762432 bytes 60.8 MiB, delta: 7634944 bytes 7.3 MiB, wrote 13.6% more than predicted
freespace: was free: 48336896 bytes 46.1 MiB, wrote: 54935552 bytes 52.4 MiB, delta: 6598656 bytes 6.3 MiB, wrote 13.7% more than predicted
freespace: was free: 40587264 bytes 38.7 MiB, wrote: 46157824 bytes 44.0 MiB, delta: 5570560 bytes 5.3 MiB, wrote 13.7% more than predicted
freespace: was free: 32841728 bytes 31.3 MiB, wrote: 37384192 bytes 35.7 MiB, delta: 4542464 bytes 4.3 MiB, wrote 13.8% more than predicted
freespace: was free: 25100288 bytes 23.9 MiB, wrote: 28618752 bytes 27.3 MiB, delta: 3518464 bytes 3.4 MiB, wrote 14.0% more than predicted
freespace: was free: 17342464 bytes 16.5 MiB, wrote: 19841024 bytes 18.9 MiB, delta: 2498560 bytes 2.4 MiB, wrote 14.4% more than predicted
freespace: was free: 9605120 bytes 9.2 MiB, wrote: 11063296 bytes 10.6 MiB, delta: 1458176 bytes 1.4 MiB, wrote 15.2% more than predicted
freespace: Test 2 finished

freespace: Test 3: gradually lessen amount of free space by trashing and fill the FS
freespace: do 10 steps, lessen free space by 7606272 bytes 7.3 MiB each time
freespace: trashing: was free: 83668992 bytes 79.8 MiB, need free: 7606272 bytes 7.3 MiB, files created: 248297, delete 225724 (90.9% of them)
freespace: was free: 70803456 bytes 67.5 MiB, wrote: 82485248 bytes 78.7 MiB, delta: 11681792 bytes 11.1 MiB, wrote 16.5% more than predicted
freespace: trashing: was free: 81080320 bytes 77.3 MiB, need free: 15212544 bytes 14.5 MiB, files created: 248711, delete 202047 (81.2% of them)
freespace: was free: 59867136 bytes 57.1 MiB, wrote: 71897088 bytes 68.6 MiB, delta: 12029952 bytes 11.5 MiB, wrote 20.1% more than predicted
freespace: trashing: was free: 82243584 bytes 78.4 MiB, need free: 22818816 bytes 21.8 MiB, files created: 248866, delete 179817 (72.3% of them)
freespace: was free: 50905088 bytes 48.5 MiB, wrote: 63168512 bytes 60.2 MiB, delta: 12263424 bytes 11.7 MiB, wrote 24.1% more than predicted
freespace: trashing: was free: 83402752 bytes 79.5 MiB, need free: 30425088 bytes 29.0 MiB, files created: 248920, delete 158114 (63.5% of them)
freespace: was free: 42651648 bytes 40.7 MiB, wrote: 55406592 bytes 52.8 MiB, delta: 12754944 bytes 12.2 MiB, wrote 29.9% more than predicted
freespace: trashing: was free: 84402176 bytes 80.5 MiB, need free: 38031360 bytes 36.3 MiB, files created: 248709, delete 136641 (54.9% of them)
freespace: was free: 35233792 bytes 33.6 MiB, wrote: 48250880 bytes 46.0 MiB, delta: 13017088 bytes 12.4 MiB, wrote 36.9% more than predicted
freespace: trashing: was free: 82530304 bytes 78.7 MiB, need free: 45637632 bytes 43.5 MiB, files created: 248778, delete 111208 (44.7% of them)
freespace: was free: 27287552 bytes 26.0 MiB, wrote: 40267776 bytes 38.4 MiB, delta: 12980224 bytes 12.4 MiB, wrote 47.6% more than predicted
freespace: trashing: was free: 85114880 bytes 81.2 MiB, need free: 53243904 bytes 50.8 MiB, files created: 248508, delete 93052 (37.4% of them)
freespace: was free: 22437888 bytes 21.4 MiB, wrote: 35328000 bytes 33.7 MiB, delta: 12890112 bytes 12.3 MiB, wrote 57.4% more than predicted
freespace: trashing: was free: 84103168 bytes 80.2 MiB, need free: 60850176 bytes 58.0 MiB, files created: 248637, delete 68743 (27.6% of them)
freespace: was free: 15536128 bytes 14.8 MiB, wrote: 28319744 bytes 27.0 MiB, delta: 12783616 bytes 12.2 MiB, wrote 82.3% more than predicted
freespace: trashing: was free: 84357120 bytes 80.4 MiB, need free: 68456448 bytes 65.3 MiB, files created: 248567, delete 46852 (18.8% of them)
freespace: was free: 9015296 bytes 8.6 MiB, wrote: 22044672 bytes 21.0 MiB, delta: 13029376 bytes 12.4 MiB, wrote 144.5% more than predicted
freespace: trashing: was free: 84942848 bytes 81.0 MiB, need free: 76062720 bytes 72.5 MiB, files created: 248636, delete 25993 (10.5% of them)
freespace: was free: 6086656 bytes 5.8 MiB, wrote: 8331264 bytes 7.9 MiB, delta: 2244608 bytes 2.1 MiB, wrote 36.9% more than predicted
freespace: Test 3 finished

freespace: finished successfully

After the change:

freespace: Test 1: fill the space we have 3 times
freespace: was free: 94048256 bytes 89.7 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 2441216 bytes 2.3 MiB, wrote 2.6% more than predicted
freespace: was free: 92246016 bytes 88.0 MiB, wrote: 96493568 bytes 92.0 MiB, delta: 4247552 bytes 4.1 MiB, wrote 4.6% more than predicted
freespace: was free: 92254208 bytes 88.0 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 4235264 bytes 4.0 MiB, wrote 4.6% more than predicted
freespace: Test 1 finished

freespace: Test 2: gradually lessen amount of free space and fill the FS
freespace: do 10 steps, lessen free space by 8386001 bytes 8.0 MiB each time
freespace: was free: 86605824 bytes 82.6 MiB, wrote: 88252416 bytes 84.2 MiB, delta: 1646592 bytes 1.6 MiB, wrote 1.9% more than predicted
freespace: was free: 78667776 bytes 75.0 MiB, wrote: 80715776 bytes 77.0 MiB, delta: 2048000 bytes 2.0 MiB, wrote 2.6% more than predicted
freespace: was free: 69615616 bytes 66.4 MiB, wrote: 71630848 bytes 68.3 MiB, delta: 2015232 bytes 1.9 MiB, wrote 2.9% more than predicted
freespace: was free: 61018112 bytes 58.2 MiB, wrote: 62783488 bytes 59.9 MiB, delta: 1765376 bytes 1.7 MiB, wrote 2.9% more than predicted
freespace: was free: 52424704 bytes 50.0 MiB, wrote: 53968896 bytes 51.5 MiB, delta: 1544192 bytes 1.5 MiB, wrote 2.9% more than predicted
freespace: was free: 43880448 bytes 41.8 MiB, wrote: 45199360 bytes 43.1 MiB, delta: 1318912 bytes 1.3 MiB, wrote 3.0% more than predicted
freespace: was free: 35332096 bytes 33.7 MiB, wrote: 36425728 bytes 34.7 MiB, delta: 1093632 bytes 1.0 MiB, wrote 3.1% more than predicted
freespace: was free: 26771456 bytes 25.5 MiB, wrote: 27643904 bytes 26.4 MiB, delta: 872448 bytes 852.0 KiB, wrote 3.3% more than predicted
freespace: was free: 18231296 bytes 17.4 MiB, wrote: 18878464 bytes 18.0 MiB, delta: 647168 bytes 632.0 KiB, wrote 3.5% more than predicted
freespace: was free: 9674752 bytes 9.2 MiB, wrote: 10088448 bytes 9.6 MiB, delta: 413696 bytes 404.0 KiB, wrote 4.3% more than predicted
freespace: Test 2 finished

freespace: Test 3: gradually lessen amount of free space by trashing and fill the FS
freespace: do 10 steps, lessen free space by 8397544 bytes 8.0 MiB each time
freespace: trashing: was free: 92372992 bytes 88.1 MiB, need free: 8397552 bytes 8.0 MiB, files created: 248296, delete 225723 (90.9% of them)
freespace: was free: 71909376 bytes 68.6 MiB, wrote: 82472960 bytes 78.7 MiB, delta: 10563584 bytes 10.1 MiB, wrote 14.7% more than predicted
freespace: trashing: was free: 88989696 bytes 84.9 MiB, need free: 16795096 bytes 16.0 MiB, files created: 248794, delete 201838 (81.1% of them)
freespace: was free: 60354560 bytes 57.6 MiB, wrote: 71782400 bytes 68.5 MiB, delta: 11427840 bytes 10.9 MiB, wrote 18.9% more than predicted
freespace: trashing: was free: 90304512 bytes 86.1 MiB, need free: 25192640 bytes 24.0 MiB, files created: 248733, delete 179342 (72.1% of them)
freespace: was free: 51187712 bytes 48.8 MiB, wrote: 62943232 bytes 60.0 MiB, delta: 11755520 bytes 11.2 MiB, wrote 23.0% more than predicted
freespace: trashing: was free: 91209728 bytes 87.0 MiB, need free: 33590184 bytes 32.0 MiB, files created: 248779, delete 157160 (63.2% of them)
freespace: was free: 42704896 bytes 40.7 MiB, wrote: 55050240 bytes 52.5 MiB, delta: 12345344 bytes 11.8 MiB, wrote 28.9% more than predicted
freespace: trashing: was free: 92700672 bytes 88.4 MiB, need free: 41987728 bytes 40.0 MiB, files created: 248848, delete 136135 (54.7% of them)
freespace: was free: 35250176 bytes 33.6 MiB, wrote: 48115712 bytes 45.9 MiB, delta: 12865536 bytes 12.3 MiB, wrote 36.5% more than predicted
freespace: trashing: was free: 93986816 bytes 89.6 MiB, need free: 50385272 bytes 48.1 MiB, files created: 248723, delete 115385 (46.4% of them)
freespace: was free: 29995008 bytes 28.6 MiB, wrote: 41582592 bytes 39.7 MiB, delta: 11587584 bytes 11.1 MiB, wrote 38.6% more than predicted
freespace: trashing: was free: 91881472 bytes 87.6 MiB, need free: 58782816 bytes 56.1 MiB, files created: 248645, delete 89569 (36.0% of them)
freespace: was free: 22511616 bytes 21.5 MiB, wrote: 34705408 bytes 33.1 MiB, delta: 12193792 bytes 11.6 MiB, wrote 54.2% more than predicted
freespace: trashing: was free: 91774976 bytes 87.5 MiB, need free: 67180360 bytes 64.1 MiB, files created: 248580, delete 66616 (26.8% of them)
freespace: was free: 16908288 bytes 16.1 MiB, wrote: 26898432 bytes 25.7 MiB, delta: 9990144 bytes 9.5 MiB, wrote 59.1% more than predicted
freespace: trashing: was free: 92450816 bytes 88.2 MiB, need free: 75577904 bytes 72.1 MiB, files created: 248654, delete 45381 (18.3% of them)
freespace: was free: 10170368 bytes 9.7 MiB, wrote: 19111936 bytes 18.2 MiB, delta: 8941568 bytes 8.5 MiB, wrote 87.9% more than predicted
freespace: trashing: was free: 93282304 bytes 89.0 MiB, need free: 83975448 bytes 80.1 MiB, files created: 248513, delete 24794 (10.0% of them)
freespace: was free: 3911680 bytes 3.7 MiB, wrote: 7872512 bytes 7.5 MiB, delta: 3960832 bytes 3.8 MiB, wrote 101.3% more than predicted
freespace: Test 3 finished

freespace: finished successfully
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

This is a preparational patch for the following statfs()
report fix.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Make free space calculation less pessimistic and more realistic,
which in turn improves 'statfs()' reports. Now it lies by 10%-20%,
instead of 20%-30% (10% more honest).

Results of "freespace" test (120MiB volume, 16KiB LEB size,
512 bytes page size). Before the change:

freespace: Test 1: fill the space we have 3 times
freespace: was free: 78274560 bytes 74.6 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 18214912 bytes 17.4 MiB, wrote 23.3% more than predicted
freespace: was free: 76754944 bytes 73.2 MiB, wrote: 96493568 bytes 92.0 MiB, delta: 19738624 bytes 18.8 MiB, wrote 25.7% more than predicted
freespace: was free: 76759040 bytes 73.2 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 19730432 bytes 18.8 MiB, wrote 25.7% more than predicted
freespace: Test 1 finished

freespace: Test 2: gradually lessen amount of free space and fill the FS
freespace: do 10 steps, lessen free space by 6977722 bytes 6.7 MiB each time
freespace: was free: 72273920 bytes 68.9 MiB, wrote: 88891392 bytes 84.8 MiB, delta: 16617472 bytes 15.8 MiB, wrote 23.0% more than predicted
freespace: was free: 66154496 bytes 63.1 MiB, wrote: 81506304 bytes 77.7 MiB, delta: 15351808 bytes 14.6 MiB, wrote 23.2% more than predicted
freespace: was free: 58732544 bytes 56.0 MiB, wrote: 72572928 bytes 69.2 MiB, delta: 13840384 bytes 13.2 MiB, wrote 23.6% more than predicted
freespace: was free: 51552256 bytes 49.2 MiB, wrote: 63754240 bytes 60.8 MiB, delta: 12201984 bytes 11.6 MiB, wrote 23.7% more than predicted
freespace: was free: 44404736 bytes 42.3 MiB, wrote: 54943744 bytes 52.4 MiB, delta: 10539008 bytes 10.1 MiB, wrote 23.7% more than predicted
freespace: was free: 37285888 bytes 35.6 MiB, wrote: 46161920 bytes 44.0 MiB, delta: 8876032 bytes 8.5 MiB, wrote 23.8% more than predicted
freespace: was free: 30171136 bytes 28.8 MiB, wrote: 37384192 bytes 35.7 MiB, delta: 7213056 bytes 6.9 MiB, wrote 23.9% more than predicted
freespace: was free: 23048192 bytes 22.0 MiB, wrote: 28606464 bytes 27.3 MiB, delta: 5558272 bytes 5.3 MiB, wrote 24.1% more than predicted
freespace: was free: 15941632 bytes 15.2 MiB, wrote: 19828736 bytes 18.9 MiB, delta: 3887104 bytes 3.7 MiB, wrote 24.4% more than predicted
freespace: was free: 8830976 bytes 8.4 MiB, wrote: 11063296 bytes 10.6 MiB, delta: 2232320 bytes 2.1 MiB, wrote 25.3% more than predicted
freespace: Test 2 finished

freespace: Test 3: gradually lessen amount of free space by trashing and fill the FS
freespace: do 10 steps, lessen free space by 6985541 bytes 6.7 MiB each time
freespace: trashing: was free: 76840960 bytes 73.3 MiB, need free: 6985550 bytes 6.7 MiB, files created: 248311, delete 225737 (90.9% of them)
freespace: was free: 65228800 bytes 62.2 MiB, wrote: 82530304 bytes 78.7 MiB, delta: 17301504 bytes 16.5 MiB, wrote 26.5% more than predicted
freespace: trashing: was free: 74485760 bytes 71.0 MiB, need free: 13971091 bytes 13.3 MiB, files created: 248712, delete 202061 (81.2% of them)
freespace: was free: 55025664 bytes 52.5 MiB, wrote: 71925760 bytes 68.6 MiB, delta: 16900096 bytes 16.1 MiB, wrote 30.7% more than predicted
freespace: trashing: was free: 75550720 bytes 72.1 MiB, need free: 20956632 bytes 20.0 MiB, files created: 248849, delete 179822 (72.3% of them)
freespace: was free: 46669824 bytes 44.5 MiB, wrote: 63197184 bytes 60.3 MiB, delta: 16527360 bytes 15.8 MiB, wrote 35.4% more than predicted
freespace: trashing: was free: 76214272 bytes 72.7 MiB, need free: 27942173 bytes 26.6 MiB, files created: 248789, delete 157576 (63.3% of them)
freespace: was free: 39129088 bytes 37.3 MiB, wrote: 55164928 bytes 52.6 MiB, delta: 16035840 bytes 15.3 MiB, wrote 41.0% more than predicted
freespace: trashing: was free: 77398016 bytes 73.8 MiB, need free: 34927714 bytes 33.3 MiB, files created: 248711, delete 136474 (54.9% of them)
freespace: was free: 32325632 bytes 30.8 MiB, wrote: 48234496 bytes 46.0 MiB, delta: 15908864 bytes 15.2 MiB, wrote 49.2% more than predicted
freespace: trashing: was free: 75796480 bytes 72.3 MiB, need free: 41913255 bytes 40.0 MiB, files created: 248674, delete 111164 (44.7% of them)
freespace: was free: 25079808 bytes 23.9 MiB, wrote: 40775680 bytes 38.9 MiB, delta: 15695872 bytes 15.0 MiB, wrote 62.6% more than predicted
freespace: trashing: was free: 78209024 bytes 74.6 MiB, need free: 48898796 bytes 46.6 MiB, files created: 248708, delete 93207 (37.5% of them)
freespace: was free: 20582400 bytes 19.6 MiB, wrote: 34844672 bytes 33.2 MiB, delta: 14262272 bytes 13.6 MiB, wrote 69.3% more than predicted
freespace: trashing: was free: 77328384 bytes 73.7 MiB, need free: 55884337 bytes 53.3 MiB, files created: 248644, delete 68951 (27.7% of them)
freespace: was free: 14368768 bytes 13.7 MiB, wrote: 28278784 bytes 27.0 MiB, delta: 13910016 bytes 13.3 MiB, wrote 96.8% more than predicted
freespace: trashing: was free: 77434880 bytes 73.8 MiB, need free: 62869878 bytes 60.0 MiB, files created: 248640, delete 46767 (18.8% of them)
freespace: was free: 8286208 bytes 7.9 MiB, wrote: 21811200 bytes 20.8 MiB, delta: 13524992 bytes 12.9 MiB, wrote 163.2% more than predicted
freespace: trashing: was free: 77856768 bytes 74.2 MiB, need free: 69855419 bytes 66.6 MiB, files created: 248576, delete 25546 (10.3% of them)
freespace: was free: 5570560 bytes 5.3 MiB, wrote: 8187904 bytes 7.8 MiB, delta: 2617344 bytes 2.5 MiB, wrote 47.0% more than predicted
freespace: Test 3 finished

freespace: finished successfully

After the change:

freespace: Test 1: fill the space we have 3 times
freespace: was free: 85204992 bytes 81.3 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 11284480 bytes 10.8 MiB, wrote 13.2% more than predicted
freespace: was free: 83554304 bytes 79.7 MiB, wrote: 96489472 bytes 92.0 MiB, delta: 12935168 bytes 12.3 MiB, wrote 15.5% more than predicted
freespace: was free: 83554304 bytes 79.7 MiB, wrote: 96493568 bytes 92.0 MiB, delta: 12939264 bytes 12.3 MiB, wrote 15.5% more than predicted
freespace: Test 1 finished

freespace: Test 2: gradually lessen amount of free space and fill the FS
freespace: do 10 steps, lessen free space by 7596218 bytes 7.2 MiB each time
freespace: was free: 78675968 bytes 75.0 MiB, wrote: 88903680 bytes 84.8 MiB, delta: 10227712 bytes 9.8 MiB, wrote 13.0% more than predicted
freespace: was free: 72015872 bytes 68.7 MiB, wrote: 81514496 bytes 77.7 MiB, delta: 9498624 bytes 9.1 MiB, wrote 13.2% more than predicted
freespace: was free: 63938560 bytes 61.0 MiB, wrote: 72589312 bytes 69.2 MiB, delta: 8650752 bytes 8.2 MiB, wrote 13.5% more than predicted
freespace: was free: 56127488 bytes 53.5 MiB, wrote: 63762432 bytes 60.8 MiB, delta: 7634944 bytes 7.3 MiB, wrote 13.6% more than predicted
freespace: was free: 48336896 bytes 46.1 MiB, wrote: 54935552 bytes 52.4 MiB, delta: 6598656 bytes 6.3 MiB, wrote 13.7% more than predicted
freespace: was free: 40587264 bytes 38.7 MiB, wrote: 46157824 bytes 44.0 MiB, delta: 5570560 bytes 5.3 MiB, wrote 13.7% more than predicted
freespace: was free: 32841728 bytes 31.3 MiB, wrote: 37384192 bytes 35.7 MiB, delta: 4542464 bytes 4.3 MiB, wrote 13.8% more than predicted
freespace: was free: 25100288 bytes 23.9 MiB, wrote: 28618752 bytes 27.3 MiB, delta: 3518464 bytes 3.4 MiB, wrote 14.0% more than predicted
freespace: was free: 17342464 bytes 16.5 MiB, wrote: 19841024 bytes 18.9 MiB, delta: 2498560 bytes 2.4 MiB, wrote 14.4% more than predicted
freespace: was free: 9605120 bytes 9.2 MiB, wrote: 11063296 bytes 10.6 MiB, delta: 1458176 bytes 1.4 MiB, wrote 15.2% more than predicted
freespace: Test 2 finished

freespace: Test 3: gradually lessen amount of free space by trashing and fill the FS
freespace: do 10 steps, lessen free space by 7606272 bytes 7.3 MiB each time
freespace: trashing: was free: 83668992 bytes 79.8 MiB, need free: 7606272 bytes 7.3 MiB, files created: 248297, delete 225724 (90.9% of them)
freespace: was free: 70803456 bytes 67.5 MiB, wrote: 82485248 bytes 78.7 MiB, delta: 11681792 bytes 11.1 MiB, wrote 16.5% more than predicted
freespace: trashing: was free: 81080320 bytes 77.3 MiB, need free: 15212544 bytes 14.5 MiB, files created: 248711, delete 202047 (81.2% of them)
freespace: was free: 59867136 bytes 57.1 MiB, wrote: 71897088 bytes 68.6 MiB, delta: 12029952 bytes 11.5 MiB, wrote 20.1% more than predicted
freespace: trashing: was free: 82243584 bytes 78.4 MiB, need free: 22818816 bytes 21.8 MiB, files created: 248866, delete 179817 (72.3% of them)
freespace: was free: 50905088 bytes 48.5 MiB, wrote: 63168512 bytes 60.2 MiB, delta: 12263424 bytes 11.7 MiB, wrote 24.1% more than predicted
freespace: trashing: was free: 83402752 bytes 79.5 MiB, need free: 30425088 bytes 29.0 MiB, files created: 248920, delete 158114 (63.5% of them)
freespace: was free: 42651648 bytes 40.7 MiB, wrote: 55406592 bytes 52.8 MiB, delta: 12754944 bytes 12.2 MiB, wrote 29.9% more than predicted
freespace: trashing: was free: 84402176 bytes 80.5 MiB, need free: 38031360 bytes 36.3 MiB, files created: 248709, delete 136641 (54.9% of them)
freespace: was free: 35233792 bytes 33.6 MiB, wrote: 48250880 bytes 46.0 MiB, delta: 13017088 bytes 12.4 MiB, wrote 36.9% more than predicted
freespace: trashing: was free: 82530304 bytes 78.7 MiB, need free: 45637632 bytes 43.5 MiB, files created: 248778, delete 111208 (44.7% of them)
freespace: was free: 27287552 bytes 26.0 MiB, wrote: 40267776 bytes 38.4 MiB, delta: 12980224 bytes 12.4 MiB, wrote 47.6% more than predicted
freespace: trashing: was free: 85114880 bytes 81.2 MiB, need free: 53243904 bytes 50.8 MiB, files created: 248508, delete 93052 (37.4% of them)
freespace: was free: 22437888 bytes 21.4 MiB, wrote: 35328000 bytes 33.7 MiB, delta: 12890112 bytes 12.3 MiB, wrote 57.4% more than predicted
freespace: trashing: was free: 84103168 bytes 80.2 MiB, need free: 60850176 bytes 58.0 MiB, files created: 248637, delete 68743 (27.6% of them)
freespace: was free: 15536128 bytes 14.8 MiB, wrote: 28319744 bytes 27.0 MiB, delta: 12783616 bytes 12.2 MiB, wrote 82.3% more than predicted
freespace: trashing: was free: 84357120 bytes 80.4 MiB, need free: 68456448 bytes 65.3 MiB, files created: 248567, delete 46852 (18.8% of them)
freespace: was free: 9015296 bytes 8.6 MiB, wrote: 22044672 bytes 21.0 MiB, delta: 13029376 bytes 12.4 MiB, wrote 144.5% more than predicted
freespace: trashing: was free: 84942848 bytes 81.0 MiB, need free: 76062720 bytes 72.5 MiB, files created: 248636, delete 25993 (10.5% of them)
freespace: was free: 6086656 bytes 5.8 MiB, wrote: 8331264 bytes 7.9 MiB, delta: 2244608 bytes 2.1 MiB, wrote 36.9% more than predicted
freespace: Test 3 finished

freespace: finished successfully
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>