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: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c9d314f..daee4ab 100644 (file)
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -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;
 }
 

diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index ba858ca..7fd3511 100644 (file)
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -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,