linux-kernel - Re: [PATCH] f2fs: add fi->commit_lock to protect commit GCed pages

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Date:   Thu, 8 Feb 2018 11:11:13 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     Chao Yu <chao@...nel.org>, <jaegeuk@...nel.org>,
        <yuchao0@...wei.com>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <shengyong1@...wei.com>, <heyunlei@...wei.com>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: add fi->commit_lock to protect commit GCed pages

Then the GCed data pages are totally mixed with the inmem atomic pages,
this will cause the atomic commit ops write the GCed data pages twice
(the first write happens in GC).

How about using the early two patches to separate the inmem data pages
and GCed data pages, and use dio_rwsem instead of this patch to fix the
dnode page problem (dnode page commited but data page are not committed
for the GCed page)?


On 2018/2/7 20:16, Chao Yu wrote:
> On 2018/2/6 11:49, Yunlong Song wrote:
>> This patch adds fi->commit_lock to avoid the case that GCed node pages
>> are committed but GCed data pages are not committed. This can avoid the
>> db file run into inconsistent state when sudden-power-off happens if
>> data pages of atomic file is allowed to be GCed before.
> 
> do_fsync:				GC:
> - mutex_lock(&fi->commit_lock);
> 					- lock_page()
> 					 - mutex_lock(&fi->commit_lock);
>   - lock_page()
> 
> 
> Well, please consider lock dependency & code complexity, IMO, reuse
> fi->dio_rwsem[WRITE] will be enough as below:
> 
> ---
>   fs/f2fs/file.c | 3 +++
>   fs/f2fs/gc.c   | 5 -----
>   2 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 672a542e5464..1bdc11feb8d0 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1711,6 +1711,8 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
> 
>   	inode_lock(inode);
> 
> +	down_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
> +
>   	if (f2fs_is_volatile_file(inode))
>   		goto err_out;
> 
> @@ -1729,6 +1731,7 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
>   		ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false);
>   	}
>   err_out:
> +	up_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
>   	inode_unlock(inode);
>   	mnt_drop_write_file(filp);
>   	return ret;
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index b9d93fd532a9..e49416283563 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -622,9 +622,6 @@ static void move_data_block(struct inode *inode, block_t bidx,
>   	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>   		goto out;
> 
> -	if (f2fs_is_atomic_file(inode))
> -		goto out;
> -
>   	if (f2fs_is_pinned_file(inode)) {
>   		f2fs_pin_file_control(inode, true);
>   		goto out;
> @@ -729,8 +726,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>   	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>   		goto out;
> 
> -	if (f2fs_is_atomic_file(inode))
> -		goto out;
>   	if (f2fs_is_pinned_file(inode)) {
>   		if (gc_type == FG_GC)
>   			f2fs_pin_file_control(inode, true);
> 

-- 
Thanks,
Yunlong Song