Commit 1a118ccf authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: use spinlock for segmap_lock instead of rwlock 



rwlock can provide better concurrency when there are much more readers than
writers because readers can hold the rwlock simultaneously.

But now, for segmap_lock rwlock in struct free_segmap_info, there is only one
reader 'mount' from below call path:
->f2fs_fill_super
  ->build_segment_manager
    ->build_dirty_segmap
      ->init_dirty_segmap
        ->find_next_inuse
          read_lock
          ...
          read_unlock

Now that our concurrency can not be improved since there is no other reader for
this lock, we do not need to use rwlock_t type for segmap_lock, let's replace it
with spinlock_t type.

Signed-off-by: default avatarChao Yu <chao2.yu@samsung.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent f1a3b98e

fs/f2fs/segment.c

+3 −3
Original line number Diff line number Diff line
@@ -800,7 +800,7 @@ static void get_new_segment(struct f2fs_sb_info *sbi, 
	int go_left = 0;

	int i;



	write_lock(&free_i->segmap_lock);

	spin_lock(&free_i->segmap_lock);



	if (!new_sec && ((*newseg + 1) % sbi->segs_per_sec)) {

		segno = find_next_zero_bit(free_i->free_segmap,
@@ -873,7 +873,7 @@ got_it: 
	f2fs_bug_on(sbi, test_bit(segno, free_i->free_segmap));

	__set_inuse(sbi, segno);

	*newseg = segno;

	write_unlock(&free_i->segmap_lock);

	spin_unlock(&free_i->segmap_lock);

}



static void reset_curseg(struct f2fs_sb_info *sbi, int type, int modified)
@@ -1923,7 +1923,7 @@ static int build_free_segmap(struct f2fs_sb_info *sbi) 
	free_i->start_segno = GET_SEGNO_FROM_SEG0(sbi, MAIN_BLKADDR(sbi));

	free_i->free_segments = 0;

	free_i->free_sections = 0;

	rwlock_init(&free_i->segmap_lock);

	spin_lock_init(&free_i->segmap_lock);

	return 0;

}

fs/f2fs/segment.h

+9 −9
Original line number Diff line number Diff line
@@ -208,7 +208,7 @@ struct free_segmap_info { 
	unsigned int start_segno;	/* start segment number logically */

	unsigned int free_segments;	/* # of free segments */

	unsigned int free_sections;	/* # of free sections */

	rwlock_t segmap_lock;		/* free segmap lock */

	spinlock_t segmap_lock;		/* free segmap lock */

	unsigned long *free_segmap;	/* free segment bitmap */

	unsigned long *free_secmap;	/* free section bitmap */

};
@@ -319,9 +319,9 @@ static inline unsigned int find_next_inuse(struct free_segmap_info *free_i, 
		unsigned int max, unsigned int segno)

{

	unsigned int ret;

	read_lock(&free_i->segmap_lock);

	spin_lock(&free_i->segmap_lock);

	ret = find_next_bit(free_i->free_segmap, max, segno);

	read_unlock(&free_i->segmap_lock);

	spin_unlock(&free_i->segmap_lock);

	return ret;

}
@@ -332,7 +332,7 @@ static inline void __set_free(struct f2fs_sb_info *sbi, unsigned int segno) 
	unsigned int start_segno = secno * sbi->segs_per_sec;

	unsigned int next;



	write_lock(&free_i->segmap_lock);

	spin_lock(&free_i->segmap_lock);

	clear_bit(segno, free_i->free_segmap);

	free_i->free_segments++;
@@ -341,7 +341,7 @@ static inline void __set_free(struct f2fs_sb_info *sbi, unsigned int segno) 
		clear_bit(secno, free_i->free_secmap);

		free_i->free_sections++;

	}

	write_unlock(&free_i->segmap_lock);

	spin_unlock(&free_i->segmap_lock);

}



static inline void __set_inuse(struct f2fs_sb_info *sbi,
@@ -363,7 +363,7 @@ static inline void __set_test_and_free(struct f2fs_sb_info *sbi, 
	unsigned int start_segno = secno * sbi->segs_per_sec;

	unsigned int next;



	write_lock(&free_i->segmap_lock);

	spin_lock(&free_i->segmap_lock);

	if (test_and_clear_bit(segno, free_i->free_segmap)) {

		free_i->free_segments++;
@@ -374,7 +374,7 @@ static inline void __set_test_and_free(struct f2fs_sb_info *sbi, 
				free_i->free_sections++;

		}

	}

	write_unlock(&free_i->segmap_lock);

	spin_unlock(&free_i->segmap_lock);

}



static inline void __set_test_and_inuse(struct f2fs_sb_info *sbi,
@@ -382,13 +382,13 @@ static inline void __set_test_and_inuse(struct f2fs_sb_info *sbi, 
{

	struct free_segmap_info *free_i = FREE_I(sbi);

	unsigned int secno = segno / sbi->segs_per_sec;

	write_lock(&free_i->segmap_lock);

	spin_lock(&free_i->segmap_lock);

	if (!test_and_set_bit(segno, free_i->free_segmap)) {

		free_i->free_segments--;

		if (!test_and_set_bit(secno, free_i->free_secmap))

			free_i->free_sections--;

	}

	write_unlock(&free_i->segmap_lock);

	spin_unlock(&free_i->segmap_lock);

}



static inline void get_sit_bitmap(struct f2fs_sb_info *sbi,

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