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Commit 81eb8d6e authored by Jaegeuk Kim's avatar Jaegeuk Kim
Browse files

f2fs: reclaim prefree segments periodically 



Previously, f2fs postpones reclaiming prefree segments into free segments
as much as possible.
However, if user writes and deletes a bunch of data without any sync or fsync
calls, some flash storages can suffer from garbage collections.

So, this patch adds the reclaiming codes to f2fs_write_node_pages and background
GC thread.

If there are a lot of prefree segments, let's do checkpoint so that f2fs
submits discard commands for the prefree regions to the flash storage.

Signed-off-by: default avatarChangman Lee <cm224.lee@samsung.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
parent aabe5136

fs/f2fs/f2fs.h

+3 −0
Original line number Diff line number Diff line
@@ -299,6 +299,9 @@ struct f2fs_sm_info { 
	unsigned int main_segments;	/* # of segments in main area */

	unsigned int reserved_segments;	/* # of reserved segments */

	unsigned int ovp_segments;	/* # of overprovision segments */



	/* a threshold to reclaim prefree segments */

	unsigned int rec_prefree_segments;

};



/*

fs/f2fs/gc.c

+5 −0
Original line number Diff line number Diff line
@@ -82,6 +82,11 @@ static int gc_thread_func(void *data) 
		/* if return value is not zero, no victim was selected */

		if (f2fs_gc(sbi))

			wait_ms = gc_th->no_gc_sleep_time;



		/* balancing prefree segments */

		if (excess_prefree_segs(sbi))

			f2fs_sync_fs(sbi->sb, true);



	} while (!kthread_should_stop());

	return 0;

}

fs/f2fs/node.c

+2 −1
Original line number Diff line number Diff line
@@ -1206,7 +1206,8 @@ static int f2fs_write_node_pages(struct address_space *mapping, 
	long nr_to_write = wbc->nr_to_write;



	/* First check balancing cached NAT entries */

	if (try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK)) {

	if (try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK) ||

				excess_prefree_segs(sbi)) {

		f2fs_sync_fs(sbi->sb, true);

		return 0;

	}

fs/f2fs/segment.c

+1 −0
Original line number Diff line number Diff line
@@ -1645,6 +1645,7 @@ int build_segment_manager(struct f2fs_sb_info *sbi) 
	sm_info->ovp_segments = le32_to_cpu(ckpt->overprov_segment_count);

	sm_info->main_segments = le32_to_cpu(raw_super->segment_count_main);

	sm_info->ssa_blkaddr = le32_to_cpu(raw_super->ssa_blkaddr);

	sm_info->rec_prefree_segments = DEF_RECLAIM_PREFREE_SEGMENTS;



	err = build_sit_info(sbi);

	if (err)

fs/f2fs/segment.h

+7 −0
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ 
#define NULL_SEGNO			((unsigned int)(~0))

#define NULL_SECNO			((unsigned int)(~0))



#define DEF_RECLAIM_PREFREE_SEGMENTS	100	/* 200MB of prefree segments */



/* L: Logical segment # in volume, R: Relative segment # in main area */

#define GET_L2R_SEGNO(free_i, segno)	(segno - free_i->start_segno)

#define GET_R2L_SEGNO(free_i, segno)	(segno + free_i->start_segno)
@@ -472,6 +474,11 @@ static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi, int freed) 
						reserved_sections(sbi)));

}



static inline bool excess_prefree_segs(struct f2fs_sb_info *sbi)

{

	return (prefree_segments(sbi) > SM_I(sbi)->rec_prefree_segments);

}



static inline int utilization(struct f2fs_sb_info *sbi)

{

	return div_u64((u64)valid_user_blocks(sbi) * 100, sbi->user_block_count);