[PATCH v3] f2fs: introduce fragment allocation mode mount option
From: Daeho Jeong
Date: Tue Aug 31 2021 - 01:10:46 EST
From: Daeho Jeong <daehojeong@xxxxxxxxxx>
Added three options into "mode=" mount option to make it possible for
developers to make the filesystem fragmented or simulate filesystem
fragmentation/after-GC situation itself. The developers use these modes
to understand filesystem fragmentation/after-GC condition well,
and eventually get some insights to handle them better.
"fragment:segment": f2fs allocates a new segment in ramdom position.
With this, we can simulate the after-GC condition.
"fragment:fixed_block" : We can scatter block allocation with
"fragment_chunk_size" and "fragment_hole_size" sysfs
nodes. f2fs will allocate <fragment_chunk_size> blocks
in a chunk and make a hole in the length of
<fragment_hole_size> by turns in a newly allocated free
segment.
"fragment:rand_block" : Working like "fragment:fixed_block" mode, but
added some randomness to both chunk and hole size. So,
f2fs will allocate 1..<fragment_chunk_size> blocks in a
chunk and make a hole in the nodes. f2fs will allocate
1..<fragment_chunk_size> blocks in a chunk and make a
hole in the length of 1..<fragment_hole_size> by turns
in a newly allocated free segment.
Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>
---
v3: divided "fragment:block" mode and fixed a race condition related to
making chunks.
v2: changed mode name and added sysfs nodes to control the fragmentation
pattern.
---
Documentation/ABI/testing/sysfs-fs-f2fs | 24 ++++++++++++++++++++
Documentation/filesystems/f2fs.rst | 20 +++++++++++++++++
fs/f2fs/f2fs.h | 21 ++++++++++++++++--
fs/f2fs/gc.c | 5 ++++-
fs/f2fs/segment.c | 29 +++++++++++++++++++++++--
fs/f2fs/segment.h | 1 +
fs/f2fs/super.c | 14 ++++++++++++
fs/f2fs/sysfs.c | 20 +++++++++++++++++
8 files changed, 129 insertions(+), 5 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index f627e705e663..d56ecfd16abf 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -512,3 +512,27 @@ Date: July 2021
Contact: "Daeho Jeong" <daehojeong@xxxxxxxxxx>
Description: You can control the multiplier value of bdi device readahead window size
between 2 (default) and 256 for POSIX_FADV_SEQUENTIAL advise option.
+
+What: /sys/fs/f2fs/<disk>/fragment_chunk_size
+Date: August 2021
+Contact: "Daeho Jeong" <daehojeong@xxxxxxxxxx>
+Description: With "mode=fragment:fixed_block" and "mode=fragment:rand_block" mount options,
+ we can scatter block allocation. Using this node, in "fragment:fixed_block"
+ mode, f2fs will allocate <fragment_chunk_size> blocks in a chunk and make
+ a hole in the length of <fragment_hole_size> by turns in a newly allocated
+ free segment. Plus, in "fragment:rand_block" mode, f2fs will allocate
+ 1..<fragment_chunk_size> blocks in a chunk and make a hole in the length of
+ 1..<fragment_hole_size> by turns. This value can be set between 1..512 and
+ the default value is 4.
+
+What: /sys/fs/f2fs/<disk>/fragment_hole_size
+Date: August 2021
+Contact: "Daeho Jeong" <daehojeong@xxxxxxxxxx>
+Description: With "mode=fragment:fixed_block" and "mode=fragment:rand_block" mount options,
+ we can scatter block allocation. Using this node, in "fragment:fixed_block"
+ mode, f2fs will allocate <fragment_chunk_size> blocks in a chunk and make
+ a hole in the length of <fragment_hole_size> by turns in a newly allocated
+ free segment. Plus, in "fragment:rand_block" mode, f2fs will allocate
+ 1..<fragment_chunk_size> blocks in a chunk and make a hole in the length of
+ 1..<fragment_hole_size> by turns. This value can be set between 1..512 and
+ the default value is 4.
diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
index 09de6ebbbdfa..c58d300d2f41 100644
--- a/Documentation/filesystems/f2fs.rst
+++ b/Documentation/filesystems/f2fs.rst
@@ -201,6 +201,26 @@ fault_type=%d Support configuring fault injection type, should be
mode=%s Control block allocation mode which supports "adaptive"
and "lfs". In "lfs" mode, there should be no random
writes towards main area.
+ "fragment:segment", "fragment:fixed_block" and "fragment:rand_block"
+ are newly added here. These are developer options for experiments
+ to make the filesystem fragmented or simulate filesystem
+ fragmentation/after-GC situation itself. The developers use these
+ modes to understand filesystem fragmentation/after-GC condition well,
+ and eventually get some insights to handle them better.
+ In "fragment:segment", f2fs allocates a new segment in ramdom
+ position. With this, we can simulate the after-GC condition.
+ In "fragment:fixed_block" and "fragment:rand_block", we can scatter
+ block allocation with "fragment_chunk_size" and "fragment_hole_size"
+ sysfs nodes. In "fragment:fixed_block" mode, f2fs will allocate
+ <fragment_chunk_size> blocks in a chunk and make a hole in the length
+ of <fragment_hole_size> by turns in a newly allocated free segment.
+ But, in "fragment:rand_block" mode, f2fs adds some randomness to
+ both chunk and hole size. So, f2fs will allocate
+ 1..<fragment_chunk_size> blocks in a chunk and make a hole in the
+ length of 1..<fragment_hole_size> by turns. With these, the newly
+ allocated blocks will be scattered throughout the whole partition.
+ Please, use these options for your experiments and we strongly
+ recommend to re-format the filesystem after using these options.
io_bits=%u Set the bit size of write IO requests. It should be set
with "mode=lfs".
usrquota Enable plain user disk quota accounting.
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c24f03e054cb..9f9368405ab1 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1285,8 +1285,11 @@ enum {
};
enum {
- FS_MODE_ADAPTIVE, /* use both lfs/ssr allocation */
- FS_MODE_LFS, /* use lfs allocation only */
+ FS_MODE_ADAPTIVE, /* use both lfs/ssr allocation */
+ FS_MODE_LFS, /* use lfs allocation only */
+ FS_MODE_FRAGMENT_SEG, /* segment fragmentation mode */
+ FS_MODE_FRAGMENT_FIXED_BLK, /* fixed block fragmentation mode */
+ FS_MODE_FRAGMENT_RAND_BLK, /* randomized block fragmentation mode */
};
enum {
@@ -1757,6 +1760,9 @@ struct f2fs_sb_info {
unsigned long seq_file_ra_mul; /* multiplier for ra_pages of seq. files in fadvise */
+ int fragment_chunk_size; /* the chunk size for block fragmentation mode */
+ int fragment_hole_size; /* the hole size for block fragmentation mode */
+
#ifdef CONFIG_F2FS_FS_COMPRESSION
struct kmem_cache *page_array_slab; /* page array entry */
unsigned int page_array_slab_size; /* default page array slab size */
@@ -3517,6 +3523,17 @@ unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi,
unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
unsigned int segno);
+#define DEF_FRAGMENT_SIZE 4
+#define MIN_FRAGMENT_SIZE 1
+#define MAX_FRAGMENT_SIZE 512
+
+static inline bool f2fs_fragment_mode(struct f2fs_sb_info *sbi)
+{
+ return F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_SEG ||
+ F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_FIXED_BLK ||
+ F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_RAND_BLK;
+}
+
/*
* checkpoint.c
*/
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 2c18443972b6..14046fb19a20 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -14,6 +14,7 @@
#include <linux/delay.h>
#include <linux/freezer.h>
#include <linux/sched/signal.h>
+#include <linux/random.h>
#include "f2fs.h"
#include "node.h"
@@ -257,7 +258,9 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
p->max_search = sbi->max_victim_search;
/* let's select beginning hot/small space first in no_heap mode*/
- if (test_opt(sbi, NOHEAP) &&
+ if (f2fs_fragment_mode(sbi))
+ p->offset = prandom_u32() % (MAIN_SECS(sbi) * sbi->segs_per_sec);
+ else if (test_opt(sbi, NOHEAP) &&
(type == CURSEG_HOT_DATA || IS_NODESEG(type)))
p->offset = 0;
else
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a135d2247415..f064e439f2e0 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -15,6 +15,7 @@
#include <linux/timer.h>
#include <linux/freezer.h>
#include <linux/sched/signal.h>
+#include <linux/random.h>
#include "f2fs.h"
#include "segment.h"
@@ -2630,6 +2631,8 @@ static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
unsigned short seg_type = curseg->seg_type;
sanity_check_seg_type(sbi, seg_type);
+ if (f2fs_fragment_mode(sbi))
+ return prandom_u32() % (MAIN_SECS(sbi) * sbi->segs_per_sec);
/* if segs_per_sec is large than 1, we need to keep original policy. */
if (__is_large_section(sbi))
@@ -2681,6 +2684,11 @@ static void new_curseg(struct f2fs_sb_info *sbi, int type, bool new_sec)
curseg->next_segno = segno;
reset_curseg(sbi, type, 1);
curseg->alloc_type = LFS;
+ if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_FIXED_BLK)
+ curseg->fragment_remained_chunk = sbi->fragment_chunk_size;
+ else if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_RAND_BLK)
+ curseg->fragment_remained_chunk =
+ prandom_u32() % sbi->fragment_chunk_size + 1;
}
static int __next_free_blkoff(struct f2fs_sb_info *sbi,
@@ -2707,12 +2715,29 @@ static int __next_free_blkoff(struct f2fs_sb_info *sbi,
static void __refresh_next_blkoff(struct f2fs_sb_info *sbi,
struct curseg_info *seg)
{
- if (seg->alloc_type == SSR)
+ if (seg->alloc_type == SSR) {
seg->next_blkoff =
__next_free_blkoff(sbi, seg->segno,
seg->next_blkoff + 1);
- else
+ } else {
seg->next_blkoff++;
+ if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_FIXED_BLK) {
+ if (--seg->fragment_remained_chunk <= 0) {
+ seg->fragment_remained_chunk =
+ sbi->fragment_chunk_size;
+ seg->next_blkoff +=
+ sbi->fragment_hole_size;
+ }
+ } else if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_RAND_BLK) {
+ /* To allocate block chunks in different sizes, use random number */
+ if (--seg->fragment_remained_chunk <= 0) {
+ seg->fragment_remained_chunk =
+ prandom_u32() % sbi->fragment_chunk_size + 1;
+ seg->next_blkoff +=
+ prandom_u32() % sbi->fragment_hole_size + 1;
+ }
+ }
+ }
}
bool f2fs_segment_has_free_slot(struct f2fs_sb_info *sbi, int segno)
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 89fff258727d..46fde9f3f28e 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -314,6 +314,7 @@ struct curseg_info {
unsigned short next_blkoff; /* next block offset to write */
unsigned int zone; /* current zone number */
unsigned int next_segno; /* preallocated segment */
+ int fragment_remained_chunk; /* remained block size in a chunk for block fragmentation mode */
bool inited; /* indicate inmem log is inited */
};
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 49e153fd8183..60067b6d9fea 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -817,6 +817,12 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
F2FS_OPTION(sbi).fs_mode = FS_MODE_ADAPTIVE;
} else if (!strcmp(name, "lfs")) {
F2FS_OPTION(sbi).fs_mode = FS_MODE_LFS;
+ } else if (!strcmp(name, "fragment:segment")) {
+ F2FS_OPTION(sbi).fs_mode = FS_MODE_FRAGMENT_SEG;
+ } else if (!strcmp(name, "fragment:fixed_block")) {
+ F2FS_OPTION(sbi).fs_mode = FS_MODE_FRAGMENT_FIXED_BLK;
+ } else if (!strcmp(name, "fragment:rand_block")) {
+ F2FS_OPTION(sbi).fs_mode = FS_MODE_FRAGMENT_RAND_BLK;
} else {
kfree(name);
return -EINVAL;
@@ -1897,6 +1903,12 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
seq_puts(seq, "adaptive");
else if (F2FS_OPTION(sbi).fs_mode == FS_MODE_LFS)
seq_puts(seq, "lfs");
+ else if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_SEG)
+ seq_puts(seq, "fragment:segment");
+ else if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_FIXED_BLK)
+ seq_puts(seq, "fragment:fixed_block");
+ else if (F2FS_OPTION(sbi).fs_mode == FS_MODE_FRAGMENT_RAND_BLK)
+ seq_puts(seq, "fragment:rand_block");
seq_printf(seq, ",active_logs=%u", F2FS_OPTION(sbi).active_logs);
if (test_opt(sbi, RESERVE_ROOT))
seq_printf(seq, ",reserve_root=%u,resuid=%u,resgid=%u",
@@ -3515,6 +3527,8 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
sbi->max_victim_search = DEF_MAX_VICTIM_SEARCH;
sbi->migration_granularity = sbi->segs_per_sec;
sbi->seq_file_ra_mul = MIN_RA_MUL;
+ sbi->fragment_chunk_size = DEF_FRAGMENT_SIZE;
+ sbi->fragment_hole_size = DEF_FRAGMENT_SIZE;
sbi->dir_level = DEF_DIR_LEVEL;
sbi->interval_time[CP_TIME] = DEF_CP_INTERVAL;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index a1a3e0f6d658..ab34b3c2e09d 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -551,6 +551,22 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
return count;
}
+ if (!strcmp(a->attr.name, "fragment_chunk_size")) {
+ if (t >= MIN_FRAGMENT_SIZE && t <= MAX_FRAGMENT_SIZE)
+ sbi->fragment_chunk_size = t;
+ else
+ return -EINVAL;
+ return count;
+ }
+
+ if (!strcmp(a->attr.name, "fragment_hole_size")) {
+ if (t >= MIN_FRAGMENT_SIZE && t <= MAX_FRAGMENT_SIZE)
+ sbi->fragment_hole_size = t;
+ else
+ return -EINVAL;
+ return count;
+ }
+
*ui = (unsigned int)t;
return count;
@@ -781,6 +797,8 @@ F2FS_RW_ATTR(ATGC_INFO, atgc_management, atgc_age_threshold, age_threshold);
F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, seq_file_ra_mul, seq_file_ra_mul);
F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_segment_mode, gc_segment_mode);
F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_reclaimed_segments, gc_reclaimed_segs);
+F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, fragment_chunk_size, fragment_chunk_size);
+F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, fragment_hole_size, fragment_hole_size);
#define ATTR_LIST(name) (&f2fs_attr_##name.attr)
static struct attribute *f2fs_attrs[] = {
@@ -859,6 +877,8 @@ static struct attribute *f2fs_attrs[] = {
ATTR_LIST(seq_file_ra_mul),
ATTR_LIST(gc_segment_mode),
ATTR_LIST(gc_reclaimed_segments),
+ ATTR_LIST(fragment_chunk_size),
+ ATTR_LIST(fragment_hole_size),
NULL,
};
ATTRIBUTE_GROUPS(f2fs);
--
2.33.0.259.gc128427fd7-goog