<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/fs/f2fs/debug.c, branch v5.10</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>f2fs: clean up kvfree</title>
<updated>2020-09-14T18:15:37+00:00</updated>
<author>
<name>Chao Yu</name>
<email>yuchao0@huawei.com</email>
</author>
<published>2020-09-14T08:47:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=c8eb702484ed5badb2b654f2c9d086e43a00b954'/>
<id>c8eb702484ed5badb2b654f2c9d086e43a00b954</id>
<content type='text'>
After commit 0b6d4ca04a86 ("f2fs: don't return vmalloc() memory from
f2fs_kmalloc()"), f2fs_k{m,z}alloc() will not return vmalloc()'ed
memory, so clean up to use kfree() instead of kvfree() to free
vmalloc()'ed memory.

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
After commit 0b6d4ca04a86 ("f2fs: don't return vmalloc() memory from
f2fs_kmalloc()"), f2fs_k{m,z}alloc() will not return vmalloc()'ed
memory, so clean up to use kfree() instead of kvfree() to free
vmalloc()'ed memory.

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: change compr_blocks of superblock info to 64bit</title>
<updated>2020-09-11T18:11:25+00:00</updated>
<author>
<name>Daeho Jeong</name>
<email>daehojeong@google.com</email>
</author>
<published>2020-08-31T02:09:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=ae999bb9a3399527bbe2c352191a0d49faa9c441'/>
<id>ae999bb9a3399527bbe2c352191a0d49faa9c441</id>
<content type='text'>
Current compr_blocks of superblock info is not 64bit value. We are
accumulating each i_compr_blocks count of inodes to this value and
those are 64bit values. So, need to change this to 64bit value.

Signed-off-by: Daeho Jeong &lt;daehojeong@google.com&gt;
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Current compr_blocks of superblock info is not 64bit value. We are
accumulating each i_compr_blocks count of inodes to this value and
those are 64bit values. So, need to change this to 64bit value.

Signed-off-by: Daeho Jeong &lt;daehojeong@google.com&gt;
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: support age threshold based garbage collection</title>
<updated>2020-09-11T18:11:15+00:00</updated>
<author>
<name>Chao Yu</name>
<email>yuchao0@huawei.com</email>
</author>
<published>2020-08-04T13:14:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=093749e296e29a4b0162eb925a6701a01e8c9a98'/>
<id>093749e296e29a4b0162eb925a6701a01e8c9a98</id>
<content type='text'>
There are several issues in current background GC algorithm:
- valid blocks is one of key factors during cost overhead calculation,
so if segment has less valid block, however even its age is young or
it locates hot segment, CB algorithm will still choose the segment as
victim, it's not appropriate.
- GCed data/node will go to existing logs, no matter in-there datas'
update frequency is the same or not, it may mix hot and cold data
again.
- GC alloctor mainly use LFS type segment, it will cost free segment
more quickly.

This patch introduces a new algorithm named age threshold based
garbage collection to solve above issues, there are three steps
mainly:

1. select a source victim:
- set an age threshold, and select candidates beased threshold:
e.g.
 0 means youngest, 100 means oldest, if we set age threshold to 80
 then select dirty segments which has age in range of [80, 100] as
 candiddates;
- set candidate_ratio threshold, and select candidates based the
ratio, so that we can shrink candidates to those oldest segments;
- select target segment with fewest valid blocks in order to
migrate blocks with minimum cost;

2. select a target victim:
- select candidates beased age threshold;
- set candidate_radius threshold, search candidates whose age is
around source victims, searching radius should less than the
radius threshold.
- select target segment with most valid blocks in order to avoid
migrating current target segment.

3. merge valid blocks from source victim into target victim with
SSR alloctor.

Test steps:
- create 160 dirty segments:
 * half of them have 128 valid blocks per segment
 * left of them have 384 valid blocks per segment
- run background GC

Benefit: GC count and block movement count both decrease obviously:

- Before:
  - Valid: 86
  - Dirty: 1
  - Prefree: 11
  - Free: 6001 (6001)

GC calls: 162 (BG: 220)
  - data segments : 160 (160)
  - node segments : 2 (2)
Try to move 41454 blocks (BG: 41454)
  - data blocks : 40960 (40960)
  - node blocks : 494 (494)

IPU: 0 blocks
SSR: 0 blocks in 0 segments
LFS: 41364 blocks in 81 segments

- After:

  - Valid: 87
  - Dirty: 0
  - Prefree: 4
  - Free: 6008 (6008)

GC calls: 75 (BG: 76)
  - data segments : 74 (74)
  - node segments : 1 (1)
Try to move 12813 blocks (BG: 12813)
  - data blocks : 12544 (12544)
  - node blocks : 269 (269)

IPU: 0 blocks
SSR: 12032 blocks in 77 segments
LFS: 855 blocks in 2 segments

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
[Jaegeuk Kim: fix a bug along with pinfile in-mem segment &amp; clean up]
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There are several issues in current background GC algorithm:
- valid blocks is one of key factors during cost overhead calculation,
so if segment has less valid block, however even its age is young or
it locates hot segment, CB algorithm will still choose the segment as
victim, it's not appropriate.
- GCed data/node will go to existing logs, no matter in-there datas'
update frequency is the same or not, it may mix hot and cold data
again.
- GC alloctor mainly use LFS type segment, it will cost free segment
more quickly.

This patch introduces a new algorithm named age threshold based
garbage collection to solve above issues, there are three steps
mainly:

1. select a source victim:
- set an age threshold, and select candidates beased threshold:
e.g.
 0 means youngest, 100 means oldest, if we set age threshold to 80
 then select dirty segments which has age in range of [80, 100] as
 candiddates;
- set candidate_ratio threshold, and select candidates based the
ratio, so that we can shrink candidates to those oldest segments;
- select target segment with fewest valid blocks in order to
migrate blocks with minimum cost;

2. select a target victim:
- select candidates beased age threshold;
- set candidate_radius threshold, search candidates whose age is
around source victims, searching radius should less than the
radius threshold.
- select target segment with most valid blocks in order to avoid
migrating current target segment.

3. merge valid blocks from source victim into target victim with
SSR alloctor.

Test steps:
- create 160 dirty segments:
 * half of them have 128 valid blocks per segment
 * left of them have 384 valid blocks per segment
- run background GC

Benefit: GC count and block movement count both decrease obviously:

- Before:
  - Valid: 86
  - Dirty: 1
  - Prefree: 11
  - Free: 6001 (6001)

GC calls: 162 (BG: 220)
  - data segments : 160 (160)
  - node segments : 2 (2)
Try to move 41454 blocks (BG: 41454)
  - data blocks : 40960 (40960)
  - node blocks : 494 (494)

IPU: 0 blocks
SSR: 0 blocks in 0 segments
LFS: 41364 blocks in 81 segments

- After:

  - Valid: 87
  - Dirty: 0
  - Prefree: 4
  - Free: 6008 (6008)

GC calls: 75 (BG: 76)
  - data segments : 74 (74)
  - node segments : 1 (1)
Try to move 12813 blocks (BG: 12813)
  - data blocks : 12544 (12544)
  - node blocks : 269 (269)

IPU: 0 blocks
SSR: 12032 blocks in 77 segments
LFS: 855 blocks in 2 segments

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
[Jaegeuk Kim: fix a bug along with pinfile in-mem segment &amp; clean up]
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: introduce inmem curseg</title>
<updated>2020-09-10T21:03:30+00:00</updated>
<author>
<name>Chao Yu</name>
<email>yuchao0@huawei.com</email>
</author>
<published>2020-08-04T13:14:45+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=d0b9e42ab6155dc05fc83f00af9f45d4dd02264d'/>
<id>d0b9e42ab6155dc05fc83f00af9f45d4dd02264d</id>
<content type='text'>
Previous implementation of aligned pinfile allocation will:
- allocate new segment on cold data log no matter whether last used
segment is partially used or not, it makes IOs more random;
- force concurrent cold data/GCed IO going into warm data area, it
can make a bad effect on hot/cold data separation;

In this patch, we introduce a new type of log named 'inmem curseg',
the differents from normal curseg is:
- it reuses existed segment type (CURSEG_XXX_NODE/DATA);
- it only exists in memory, its segno, blkofs, summary will not b
 persisted into checkpoint area;

With this new feature, we can enhance scalability of log, special
allocators can be created for purposes:
- pure lfs allocator for aligned pinfile allocation or file
defragmentation
- pure ssr allocator for later feature

So that, let's update aligned pinfile allocation to use this new
inmem curseg fwk.

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Previous implementation of aligned pinfile allocation will:
- allocate new segment on cold data log no matter whether last used
segment is partially used or not, it makes IOs more random;
- force concurrent cold data/GCed IO going into warm data area, it
can make a bad effect on hot/cold data separation;

In this patch, we introduce a new type of log named 'inmem curseg',
the differents from normal curseg is:
- it reuses existed segment type (CURSEG_XXX_NODE/DATA);
- it only exists in memory, its segno, blkofs, summary will not b
 persisted into checkpoint area;

With this new feature, we can enhance scalability of log, special
allocators can be created for purposes:
- pure lfs allocator for aligned pinfile allocation or file
defragmentation
- pure ssr allocator for later feature

So that, let's update aligned pinfile allocation to use this new
inmem curseg fwk.

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: show more debug info for per-temperature log</title>
<updated>2020-07-08T04:51:45+00:00</updated>
<author>
<name>Chao Yu</name>
<email>yuchao0@huawei.com</email>
</author>
<published>2020-06-28T02:58:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0759e2c151f47b1362b15d544aca903d4ed74f88'/>
<id>0759e2c151f47b1362b15d544aca903d4ed74f88</id>
<content type='text'>
- Add to account and show per-log dirty_seg, full_seg and valid_blocks
in debugfs.
- reformat printed info.

    TYPE            segno    secno   zoneno  dirty_seg   full_seg  valid_blk
  - COLD   data:     1523     1523     1523          1          0        399
  - WARM   data:      769      769      769         20        255     133098
  - HOT    data:      767      767      767          9          0        167
  - Dir   dnode:       22       22       22          3          0         70
  - File  dnode:      722      722      722         14         10       6505
  - Indir nodes:        2        2        2          1          0          3

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
- Add to account and show per-log dirty_seg, full_seg and valid_blocks
in debugfs.
- reformat printed info.

    TYPE            segno    secno   zoneno  dirty_seg   full_seg  valid_blk
  - COLD   data:     1523     1523     1523          1          0        399
  - WARM   data:      769      769      769         20        255     133098
  - HOT    data:      767      767      767          9          0        167
  - Dir   dnode:       22       22       22          3          0         70
  - File  dnode:      722      722      722         14         10       6505
  - Indir nodes:        2        2        2          1          0          3

Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: show mounted time</title>
<updated>2020-03-19T18:41:25+00:00</updated>
<author>
<name>Jaegeuk Kim</name>
<email>jaegeuk@kernel.org</email>
</author>
<published>2020-02-26T03:08:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=a7e679b53393c76d4427f4085ec9d114f06cac5a'/>
<id>a7e679b53393c76d4427f4085ec9d114f06cac5a</id>
<content type='text'>
Let's show mounted time.

Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Let's show mounted time.

Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: Add f2fs stats to sysfs</title>
<updated>2020-01-23T17:24:25+00:00</updated>
<author>
<name>Hridya Valsaraju</name>
<email>hridya@google.com</email>
</author>
<published>2020-01-22T18:51:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=fc7100ea2a52fcf200be75421bfd32652827d287'/>
<id>fc7100ea2a52fcf200be75421bfd32652827d287</id>
<content type='text'>
Currently f2fs stats are only available from /d/f2fs/status. This patch
adds some of the f2fs stats to sysfs so that they are accessible even
when debugfs is not mounted.

The following sysfs nodes are added:
-/sys/fs/f2fs/&lt;disk&gt;/free_segments
-/sys/fs/f2fs/&lt;disk&gt;/cp_foreground_calls
-/sys/fs/f2fs/&lt;disk&gt;/cp_background_calls
-/sys/fs/f2fs/&lt;disk&gt;/gc_foreground_calls
-/sys/fs/f2fs/&lt;disk&gt;/gc_background_calls
-/sys/fs/f2fs/&lt;disk&gt;/moved_blocks_foreground
-/sys/fs/f2fs/&lt;disk&gt;/moved_blocks_background
-/sys/fs/f2fs/&lt;disk&gt;/avg_vblocks

Signed-off-by: Hridya Valsaraju &lt;hridya@google.com&gt;
[Jaegeuk Kim: allow STAT_FS without DEBUG_FS]
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Currently f2fs stats are only available from /d/f2fs/status. This patch
adds some of the f2fs stats to sysfs so that they are accessible even
when debugfs is not mounted.

The following sysfs nodes are added:
-/sys/fs/f2fs/&lt;disk&gt;/free_segments
-/sys/fs/f2fs/&lt;disk&gt;/cp_foreground_calls
-/sys/fs/f2fs/&lt;disk&gt;/cp_background_calls
-/sys/fs/f2fs/&lt;disk&gt;/gc_foreground_calls
-/sys/fs/f2fs/&lt;disk&gt;/gc_background_calls
-/sys/fs/f2fs/&lt;disk&gt;/moved_blocks_foreground
-/sys/fs/f2fs/&lt;disk&gt;/moved_blocks_background
-/sys/fs/f2fs/&lt;disk&gt;/avg_vblocks

Signed-off-by: Hridya Valsaraju &lt;hridya@google.com&gt;
[Jaegeuk Kim: allow STAT_FS without DEBUG_FS]
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: support data compression</title>
<updated>2020-01-18T00:48:07+00:00</updated>
<author>
<name>Chao Yu</name>
<email>yuchao0@huawei.com</email>
</author>
<published>2019-11-01T10:07:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=4c8ff7095bef64fc47e996a938f7d57f9e077da3'/>
<id>4c8ff7095bef64fc47e996a938f7d57f9e077da3</id>
<content type='text'>
This patch tries to support compression in f2fs.

- New term named cluster is defined as basic unit of compression, file can
be divided into multiple clusters logically. One cluster includes 4 &lt;&lt; n
(n &gt;= 0) logical pages, compression size is also cluster size, each of
cluster can be compressed or not.

- In cluster metadata layout, one special flag is used to indicate cluster
is compressed one or normal one, for compressed cluster, following metadata
maps cluster to [1, 4 &lt;&lt; n - 1] physical blocks, in where f2fs stores
data including compress header and compressed data.

- In order to eliminate write amplification during overwrite, F2FS only
support compression on write-once file, data can be compressed only when
all logical blocks in file are valid and cluster compress ratio is lower
than specified threshold.

- To enable compression on regular inode, there are three ways:
* chattr +c file
* chattr +c dir; touch dir/file
* mount w/ -o compress_extension=ext; touch file.ext

Compress metadata layout:
                             [Dnode Structure]
             +-----------------------------------------------+
             | cluster 1 | cluster 2 | ......... | cluster N |
             +-----------------------------------------------+
             .           .                       .           .
       .                       .                .                      .
  .         Compressed Cluster       .        .        Normal Cluster            .
+----------+---------+---------+---------+  +---------+---------+---------+---------+
|compr flag| block 1 | block 2 | block 3 |  | block 1 | block 2 | block 3 | block 4 |
+----------+---------+---------+---------+  +---------+---------+---------+---------+
           .                             .
         .                                           .
       .                                                           .
      +-------------+-------------+----------+----------------------------+
      | data length | data chksum | reserved |      compressed data       |
      +-------------+-------------+----------+----------------------------+

Changelog:

20190326:
- fix error handling of read_end_io().
- remove unneeded comments in f2fs_encrypt_one_page().

20190327:
- fix wrong use of f2fs_cluster_is_full() in f2fs_mpage_readpages().
- don't jump into loop directly to avoid uninitialized variables.
- add TODO tag in error path of f2fs_write_cache_pages().

20190328:
- fix wrong merge condition in f2fs_read_multi_pages().
- check compressed file in f2fs_post_read_required().

20190401
- allow overwrite on non-compressed cluster.
- check cluster meta before writing compressed data.

20190402
- don't preallocate blocks for compressed file.

- add lz4 compress algorithm
- process multiple post read works in one workqueue
  Now f2fs supports processing post read work in multiple workqueue,
  it shows low performance due to schedule overhead of multiple
  workqueue executing orderly.

20190921
- compress: support buffered overwrite
C: compress cluster flag
V: valid block address
N: NEW_ADDR

One cluster contain 4 blocks

 before overwrite   after overwrite

- VVVV		-&gt;	CVNN
- CVNN		-&gt;	VVVV

- CVNN		-&gt;	CVNN
- CVNN		-&gt;	CVVV

- CVVV		-&gt;	CVNN
- CVVV		-&gt;	CVVV

20191029
- add kconfig F2FS_FS_COMPRESSION to isolate compression related
codes, add kconfig F2FS_FS_{LZO,LZ4} to cover backend algorithm.
note that: will remove lzo backend if Jaegeuk agreed that too.
- update codes according to Eric's comments.

20191101
- apply fixes from Jaegeuk

20191113
- apply fixes from Jaegeuk
- split workqueue for fsverity

20191216
- apply fixes from Jaegeuk

20200117
- fix to avoid NULL pointer dereference

[Jaegeuk Kim]
- add tracepoint for f2fs_{,de}compress_pages()
- fix many bugs and add some compression stats
- fix overwrite/mmap bugs
- address 32bit build error, reported by Geert.
- bug fixes when handling errors and i_compressed_blocks

Reported-by: &lt;noreply@ellerman.id.au&gt;
Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This patch tries to support compression in f2fs.

- New term named cluster is defined as basic unit of compression, file can
be divided into multiple clusters logically. One cluster includes 4 &lt;&lt; n
(n &gt;= 0) logical pages, compression size is also cluster size, each of
cluster can be compressed or not.

- In cluster metadata layout, one special flag is used to indicate cluster
is compressed one or normal one, for compressed cluster, following metadata
maps cluster to [1, 4 &lt;&lt; n - 1] physical blocks, in where f2fs stores
data including compress header and compressed data.

- In order to eliminate write amplification during overwrite, F2FS only
support compression on write-once file, data can be compressed only when
all logical blocks in file are valid and cluster compress ratio is lower
than specified threshold.

- To enable compression on regular inode, there are three ways:
* chattr +c file
* chattr +c dir; touch dir/file
* mount w/ -o compress_extension=ext; touch file.ext

Compress metadata layout:
                             [Dnode Structure]
             +-----------------------------------------------+
             | cluster 1 | cluster 2 | ......... | cluster N |
             +-----------------------------------------------+
             .           .                       .           .
       .                       .                .                      .
  .         Compressed Cluster       .        .        Normal Cluster            .
+----------+---------+---------+---------+  +---------+---------+---------+---------+
|compr flag| block 1 | block 2 | block 3 |  | block 1 | block 2 | block 3 | block 4 |
+----------+---------+---------+---------+  +---------+---------+---------+---------+
           .                             .
         .                                           .
       .                                                           .
      +-------------+-------------+----------+----------------------------+
      | data length | data chksum | reserved |      compressed data       |
      +-------------+-------------+----------+----------------------------+

Changelog:

20190326:
- fix error handling of read_end_io().
- remove unneeded comments in f2fs_encrypt_one_page().

20190327:
- fix wrong use of f2fs_cluster_is_full() in f2fs_mpage_readpages().
- don't jump into loop directly to avoid uninitialized variables.
- add TODO tag in error path of f2fs_write_cache_pages().

20190328:
- fix wrong merge condition in f2fs_read_multi_pages().
- check compressed file in f2fs_post_read_required().

20190401
- allow overwrite on non-compressed cluster.
- check cluster meta before writing compressed data.

20190402
- don't preallocate blocks for compressed file.

- add lz4 compress algorithm
- process multiple post read works in one workqueue
  Now f2fs supports processing post read work in multiple workqueue,
  it shows low performance due to schedule overhead of multiple
  workqueue executing orderly.

20190921
- compress: support buffered overwrite
C: compress cluster flag
V: valid block address
N: NEW_ADDR

One cluster contain 4 blocks

 before overwrite   after overwrite

- VVVV		-&gt;	CVNN
- CVNN		-&gt;	VVVV

- CVNN		-&gt;	CVNN
- CVNN		-&gt;	CVVV

- CVVV		-&gt;	CVNN
- CVVV		-&gt;	CVVV

20191029
- add kconfig F2FS_FS_COMPRESSION to isolate compression related
codes, add kconfig F2FS_FS_{LZO,LZ4} to cover backend algorithm.
note that: will remove lzo backend if Jaegeuk agreed that too.
- update codes according to Eric's comments.

20191101
- apply fixes from Jaegeuk

20191113
- apply fixes from Jaegeuk
- split workqueue for fsverity

20191216
- apply fixes from Jaegeuk

20200117
- fix to avoid NULL pointer dereference

[Jaegeuk Kim]
- add tracepoint for f2fs_{,de}compress_pages()
- fix many bugs and add some compression stats
- fix overwrite/mmap bugs
- address 32bit build error, reported by Geert.
- bug fixes when handling errors and i_compressed_blocks

Reported-by: &lt;noreply@ellerman.id.au&gt;
Signed-off-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>f2fs: cleanup duplicate stats for atomic files</title>
<updated>2020-01-15T21:43:48+00:00</updated>
<author>
<name>Sahitya Tummala</name>
<email>stummala@codeaurora.org</email>
</author>
<published>2019-12-05T03:22:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0e6d01643c207fdcd77b9b40c29cbe1c63f03c15'/>
<id>0e6d01643c207fdcd77b9b40c29cbe1c63f03c15</id>
<content type='text'>
Remove duplicate sbi-&gt;aw_cnt stats counter that tracks
the number of atomic files currently opened (it also shows
incorrect value sometimes). Use more relit lable sbi-&gt;atomic_files
to show in the stats.

Signed-off-by: Sahitya Tummala &lt;stummala@codeaurora.org&gt;
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Remove duplicate sbi-&gt;aw_cnt stats counter that tracks
the number of atomic files currently opened (it also shows
incorrect value sometimes). Use more relit lable sbi-&gt;atomic_files
to show in the stats.

Signed-off-by: Sahitya Tummala &lt;stummala@codeaurora.org&gt;
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>fs: f2fs: Remove unnecessary checks of SM_I(sbi) in update_general_status()</title>
<updated>2019-08-23T14:57:12+00:00</updated>
<author>
<name>Jia-Ju Bai</name>
<email>baijiaju1990@gmail.com</email>
</author>
<published>2019-07-26T03:45:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=280fd422958187ac5f069c08d84dd65f7f87c2e6'/>
<id>280fd422958187ac5f069c08d84dd65f7f87c2e6</id>
<content type='text'>
In fill_super() and put_super(), f2fs_destroy_stats() is called
in prior to f2fs_destroy_segment_manager(), so if current
sbi can still be visited in global stat list, SM_I(sbi) should be
released yet.
For this reason, SM_I(sbi) does not need to be checked in
update_general_status().
Thank Chao Yu for advice.

Signed-off-by: Jia-Ju Bai &lt;baijiaju1990@gmail.com&gt;
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In fill_super() and put_super(), f2fs_destroy_stats() is called
in prior to f2fs_destroy_segment_manager(), so if current
sbi can still be visited in global stat list, SM_I(sbi) should be
released yet.
For this reason, SM_I(sbi) does not need to be checked in
update_general_status().
Thank Chao Yu for advice.

Signed-off-by: Jia-Ju Bai &lt;baijiaju1990@gmail.com&gt;
Reviewed-by: Chao Yu &lt;yuchao0@huawei.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk@kernel.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
