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Message-id: <001301cee4e3$cdd41320$697c3960$@samsung.com>
Date: Tue, 19 Nov 2013 12:56:08 +0800
From: Chao Yu <chao2.yu@...sung.com>
To: jaegeuk.kim@...sung.com
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: RE: [f2fs-dev] [PATCH] f2fs: split sbi->write_mutex for DATA/NODE/META
to avoid unnecessary race
Hi
> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk.kim@...sung.com]
> Sent: Tuesday, November 19, 2013 11:36 AM
> To: Chao Yu
> Cc: linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org;
> linux-f2fs-devel@...ts.sourceforge.net
> Subject: Re: [f2fs-dev] [PATCH] f2fs: split sbi->write_mutex for DATA/NODE/META to
> avoid unnecessary race
>
> Hi,
>
> I think we don't need to make two patches for this.
> How about this?
This could be reasonable,
And I will refer to this patch.
>
> From 71c27f78e72d680edcd7b1c0917842343044653c Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> Date: Mon, 18 Nov 2013 17:16:17 +0900
> Subject: [PATCH] f2fs: use sbi->write_mutex for write bios
>
> This patch removes an unnecessary semaphore (i.e., sbi->bio_sem).
> There is no reason to use the semaphore when f2fs submits read and write
> IOs.
> Instead, let's use a write mutex and cover the sbi->bio[] by the lock.
>
> Change log from v1:
> o split write_mutex suggested by Chao Yu
>
> Chao described,
> "All DATA/NODE/META bio buffers in superblock is protected by
> 'sbi->write_mutex', but each bio buffer area is independent, So we
> should split write_mutex to three for DATA/NODE/META."
>
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> ---
> fs/f2fs/data.c | 4 ----
> fs/f2fs/f2fs.h | 2 +-
> fs/f2fs/segment.c | 13 +++++++++----
> fs/f2fs/super.c | 6 +++++-
> 4 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 076a60c..5920639 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 6a49554..6e67f28 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -374,7 +374,7 @@ 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 write_mutex[NR_PAGE_TYPE]; /* mutex for writing IOs */
>
> /* for checkpoint */
> struct f2fs_checkpoint *ckpt; /* raw checkpoint pointer */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index dad5f1a..119af0b 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -871,9 +871,14 @@ 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);
> + enum page_type btype = PAGE_TYPE_OF_BIO(type);
> +
> + if (!sbi->bio[btype])
> + return;
> +
> + mutex_lock(&sbi->write_mutex[btype]);
> do_submit_bio(sbi, type, sync);
> - up_write(&sbi->bio_sem);
> + mutex_unlock(&sbi->write_mutex[btype]);
> }
>
> static void submit_write_page(struct f2fs_sb_info *sbi, struct page
> *page,
> @@ -884,7 +889,7 @@ 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->write_mutex[type]);
>
> inc_page_count(sbi, F2FS_WRITEBACK);
>
> @@ -919,7 +924,7 @@ retry:
>
> sbi->last_block_in_bio[type] = blk_addr;
>
> - up_write(&sbi->bio_sem);
> + mutex_unlock(&sbi->write_mutex[type]);
> trace_f2fs_submit_write_page(page, blk_addr, type);
> }
>
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index a022412..e194578 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -820,6 +820,7 @@ static int f2fs_fill_super(struct super_block *sb,
> void *data, int silent)
> struct buffer_head *raw_super_buf;
> struct inode *root;
> long err = -EINVAL;
> + int i;
>
> /* allocate memory for f2fs-specific super block info */
> sbi = kzalloc(sizeof(struct f2fs_sb_info), GFP_KERNEL);
> @@ -876,7 +877,10 @@ 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);
> +
> + for (i = 0; i < NR_PAGE_TYPE; i++)
> + mutex_init(&sbi->write_mutex[i]);
> +
> init_rwsem(&sbi->cp_rwsem);
> init_waitqueue_head(&sbi->cp_wait);
> init_sb_info(sbi);
> --
> 1.8.4.474.g128a96c
>
>
>
> --
> Jaegeuk Kim
> Samsung
--
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