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Message-ID: <7953c617-2f74-faa4-2aa4-c6ef9de2c28e@huawei.com>
Date: Sat, 30 Mar 2024 16:04:03 +0800
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Subject: Re: [PATCH] ext4: clear EXT4_GROUP_INFO_WAS_TRIMMED_BIT even mount
 with discard
To: Jan Kara <jack@suse.cz>, yangerkun <yangerkun@huaweicloud.com>, "Theodore
 Y . Ts'o" <tytso@mit.edu>
CC: <tytso@mit.edu>, <adilger.kernel@dilger.ca>, <boyu.mt@taobao.com>,
	<linux-ext4@vger.kernel.org>
References: <20231230070654.178638-1-yangerkun@huaweicloud.com>
 <20240221111852.olo7jeycctz7xntj@quack3>
From: yangerkun <yangerkun@huawei.com>
In-Reply-To: <20240221111852.olo7jeycctz7xntj@quack3>
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Hi, Ted,

Ping for this patch.


在 2024/2/21 19:18, Jan Kara 写道:
> On Sat 30-12-23 15:06:54, yangerkun wrote:
>> Commit 3d56b8d2c74c ("ext4: Speed up FITRIM by recording flags in
>> ext4_group_info") speed up fstrim by skipping trim trimmed group. We
>> also has the chance to clear trimmed once there exists some block free
>> for this group(mount without discard), and the next trim for this group
>> will work well too.
>>
>> For mount with discard, we will issue dicard when we free blocks, so
>> leave trimmed flag keep alive to skip useless trim trigger from
>> userspace seems reasonable. But for some case like ext4 build on
>> dm-thinpool(ext4 blocksize 4K, pool blocksize 128K), discard from ext4
>> maybe unaligned for dm thinpool, and thinpool will just finish this
>> discard(see process_discard_bio when begein equals to end) without
>> actually process discard. For this case, trim from userspace can really
>> help us to free some thinpool block.
>>
>> So convert to clear trimmed flag for all case no matter mounted with
>> discard or not.
>>
>> Fixes: 3d56b8d2c74c ("ext4: Speed up FITRIM by recording flags in ext4_group_info")
>> Signed-off-by: yangerkun <yangerkun@huaweicloud.com>
> 
> Thanks for the fix. It looks good. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> 								Honza
> 
>> ---
>>   fs/ext4/mballoc.c | 10 ++++------
>>   1 file changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index d72b5e3c92ec..69240ae775f1 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -3855,11 +3855,8 @@ static void ext4_free_data_in_buddy(struct super_block *sb,
>>   	/*
>>   	 * Clear the trimmed flag for the group so that the next
>>   	 * ext4_trim_fs can trim it.
>> -	 * If the volume is mounted with -o discard, online discard
>> -	 * is supported and the free blocks will be trimmed online.
>>   	 */
>> -	if (!test_opt(sb, DISCARD))
>> -		EXT4_MB_GRP_CLEAR_TRIMMED(db);
>> +	EXT4_MB_GRP_CLEAR_TRIMMED(db);
>>   
>>   	if (!db->bb_free_root.rb_node) {
>>   		/* No more items in the per group rb tree
>> @@ -6481,8 +6478,9 @@ static void ext4_mb_clear_bb(handle_t *handle, struct inode *inode,
>>   					 " group:%u block:%d count:%lu failed"
>>   					 " with %d", block_group, bit, count,
>>   					 err);
>> -		} else
>> -			EXT4_MB_GRP_CLEAR_TRIMMED(e4b.bd_info);
>> +		}
>> +
>> +		EXT4_MB_GRP_CLEAR_TRIMMED(e4b.bd_info);
>>   
>>   		ext4_lock_group(sb, block_group);
>>   		mb_free_blocks(inode, &e4b, bit, count_clusters);
>> -- 
>> 2.39.2
>>
>>