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Subject: Re: [PATCH] f2fs: prevent meta updates while checkpoint is in
 progress
To:     Jaegeuk Kim <jaegeuk@kernel.org>,
        Sahitya Tummala <stummala@codeaurora.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>
References: <1585219019-24831-1-git-send-email-stummala@codeaurora.org>
 <20200327192412.GA186975@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <397da8a6-fdb4-9637-c6ea-803492c408a2@huawei.com>
Date:   Sat, 28 Mar 2020 16:38:00 +0800
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Hi all,

On 2020/3/28 3:24, Jaegeuk Kim wrote:
> Hi Sahitya,
> 
> On 03/26, Sahitya Tummala wrote:
>> allocate_segment_for_resize() can cause metapage updates if
>> it requires to change the current node/data segments for resizing.
>> Stop these meta updates when there is a checkpoint already
>> in progress to prevent inconsistent CP data.
> 
> Doesn't freeze|thaw_bdev(sbi->sb->s_bdev); work for you?

That can avoid foreground ops racing? rather than background ops like
balance_fs() from kworker?

BTW, I found that {freeze,thaw}_bdev is not enough to freeze all
foreground fs ops, it needs to use {freeze,thaw}_super instead.

---
 fs/f2fs/gc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 26248c8936db..acdc8b99b543 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1538,7 +1538,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
 		return -EINVAL;
 	}

-	freeze_bdev(sbi->sb->s_bdev);
+	freeze_super(sbi->sb);

 	shrunk_blocks = old_block_count - block_count;
 	secs = div_u64(shrunk_blocks, BLKS_PER_SEC(sbi));
@@ -1551,7 +1551,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
 		sbi->user_block_count -= shrunk_blocks;
 	spin_unlock(&sbi->stat_lock);
 	if (err) {
-		thaw_bdev(sbi->sb->s_bdev, sbi->sb);
+		thaw_super(sbi->sb);
 		return err;
 	}

@@ -1613,6 +1613,6 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
 	}
 	clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
 	mutex_unlock(&sbi->resize_mutex);
-	thaw_bdev(sbi->sb->s_bdev, sbi->sb);
+	thaw_super(sbi->sb);
 	return err;
 }
-- 
2.18.0.rc1

> 
>>
>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
>> ---
>>  fs/f2fs/gc.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index 5bca560..6122bad 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -1399,8 +1399,10 @@ static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
>>  	int err = 0;
>>  
>>  	/* Move out cursegs from the target range */
>> +	f2fs_lock_op(sbi);
>>  	for (type = CURSEG_HOT_DATA; type < NR_CURSEG_TYPE; type++)
>>  		allocate_segment_for_resize(sbi, type, start, end);
>> +	f2fs_unlock_op(sbi);
>>  
>>  	/* do GC to move out valid blocks in the range */
>>  	for (segno = start; segno <= end; segno += sbi->segs_per_sec) {
>> -- 
>> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
> .
>