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authorDaeho Jeong <daehojeong@google.com>2021-09-29 21:12:03 +0300
committerJaegeuk Kim <jaegeuk@kernel.org>2021-10-27 00:04:30 +0300
commit6691d940b0e09dd1564130e7a354d6deaf05d009 (patch)
treeae609ea58abdfd7ce7c73e72f82d39226f2de3a9 /fs/f2fs/segment.c
parent84eab2a899f28137e51a36861ed2df9579f54ebe (diff)
downloadlinux-6691d940b0e09dd1564130e7a354d6deaf05d009.tar.xz
f2fs: introduce fragment allocation mode mount option
Added two options into "mode=" mount option to make it possible for developers to 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:block" : We can scatter block allocation with "max_fragment_chunk" and "max_fragment_hole" sysfs nodes. f2fs will allocate 1..<max_fragment_chunk> blocks in a chunk and make a hole in the length of 1..<max_fragment_hole> by turns in a newly allocated free segment. Plus, this mode implicitly enables "fragment:segment" option for more randomness. Reviewed-by: Chao Yu <chao@kernel.org> Signed-off-by: Daeho Jeong <daehojeong@google.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/f2fs/segment.c')
-rw-r--r--fs/f2fs/segment.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 3189537a19dc..bdaf5fbdfb18 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"
@@ -2649,6 +2650,8 @@ 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_need_rand_seg(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))
@@ -2700,6 +2703,9 @@ 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_BLK)
+ curseg->fragment_remained_chunk =
+ prandom_u32() % sbi->max_fragment_chunk + 1;
}
static int __next_free_blkoff(struct f2fs_sb_info *sbi,
@@ -2726,12 +2732,22 @@ 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_BLK) {
+ /* To allocate block chunks in different sizes, use random number */
+ if (--seg->fragment_remained_chunk <= 0) {
+ seg->fragment_remained_chunk =
+ prandom_u32() % sbi->max_fragment_chunk + 1;
+ seg->next_blkoff +=
+ prandom_u32() % sbi->max_fragment_hole + 1;
+ }
+ }
+ }
}
bool f2fs_segment_has_free_slot(struct f2fs_sb_info *sbi, int segno)