[PATCH] f2fs: use mutex rather than the rw_sem

[Gu Zheng]

Use mutex rather than the rw_sem to protect bio related fields,
because it's needless to take the read_sem in the read path.


Signed-off-by: Gu Zheng <guz.f...@cn.fujitsu.com>
---
 fs/f2fs/data.c    |    4 ----
 fs/f2fs/f2fs.h    |    2 +-
 fs/f2fs/segment.c |    8 ++++----
 fs/f2fs/super.c   |    2 +-
 4 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index aa3438c..b4e4c7e 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -383,8 +383,6 @@ int f2fs_readpage(struct f2fs_sb_info *sbi, struct page 
*page,
 
        trace_f2fs_readpage(page, blk_addr, type);
 
-       down_read(&sbi->bio_sem);
-
        /* Allocate a new bio */
        bio = f2fs_bio_alloc(bdev, 1);
 
@@ -394,13 +392,11 @@ int f2fs_readpage(struct f2fs_sb_info *sbi, struct page 
*page,
 
        if (bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) {
                bio_put(bio);
-               up_read(&sbi->bio_sem);
                f2fs_put_page(page, 1);
                return -EFAULT;
        }
 
        submit_bio(type, bio);
-       up_read(&sbi->bio_sem);
        return 0;
 }
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 89dc750..78a0054 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -361,7 +361,7 @@ struct f2fs_sb_info {
        struct f2fs_sm_info *sm_info;           /* segment manager */
        struct bio *bio[NR_PAGE_TYPE];          /* bios to merge */
        sector_t last_block_in_bio[NR_PAGE_TYPE];       /* last block number */
-       struct rw_semaphore bio_sem;            /* IO semaphore */
+       struct mutex bio_mutex;                 /* IO write mutex */
 
        /* for checkpoint */
        struct f2fs_checkpoint *ckpt;           /* raw checkpoint pointer */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fa284d3..e91f65c 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -653,9 +653,9 @@ static void do_submit_bio(struct f2fs_sb_info *sbi,
 
 void f2fs_submit_bio(struct f2fs_sb_info *sbi, enum page_type type, bool sync)
 {
-       down_write(&sbi->bio_sem);
+       mutex_lock(&sbi->bio_mutex);
        do_submit_bio(sbi, type, sync);
-       up_write(&sbi->bio_sem);
+       mutex_unlock(&sbi->bio_mutex);
 }
 
 static void submit_write_page(struct f2fs_sb_info *sbi, struct page *page,
@@ -666,7 +666,7 @@ static void submit_write_page(struct f2fs_sb_info *sbi, 
struct page *page,
 
        verify_block_addr(sbi, blk_addr);
 
-       down_write(&sbi->bio_sem);
+       mutex_lock(&sbi->bio_mutex);
 
        inc_page_count(sbi, F2FS_WRITEBACK);
 
@@ -701,7 +701,7 @@ retry:
 
        sbi->last_block_in_bio[type] = blk_addr;
 
-       up_write(&sbi->bio_sem);
+       mutex_unlock(&sbi->bio_mutex);
        trace_f2fs_submit_write_page(page, blk_addr, type);
 }
 
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index bafff72..fab3550 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -874,7 +874,7 @@ static int f2fs_fill_super(struct super_block *sb, void 
*data, int silent)
        mutex_init(&sbi->node_write);
        sbi->por_doing = false;
        spin_lock_init(&sbi->stat_lock);
-       init_rwsem(&sbi->bio_sem);
+       mutex_init(&sbi->bio_mutex);
        init_rwsem(&sbi->cp_rwsem);
        init_waitqueue_head(&sbi->cp_wait);
        init_sb_info(sbi);
-- 
1.7.7

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