linux-kernel - Re: [PATCH 2/2] f2fs: fix missing small discard in fstrim

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Message-ID: <fd75a391-3dd1-4411-806e-0bbb363fcba3@vivo.com>
Date: Fri, 3 Jan 2025 07:00:08 +0000
From: Chunhai Guo <guochunhai@...o.com>
To: Chao Yu <chao@...nel.org>, Chunhai Guo <guochunhai@...o.com>,
	"jaegeuk@...nel.org" <jaegeuk@...nel.org>
CC: "linux-f2fs-devel@...ts.sourceforge.net"
	<linux-f2fs-devel@...ts.sourceforge.net>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] f2fs: fix missing small discard in fstrim

在 1/3/2025 11:36 AM, Chao Yu 写道:
> On 2025/1/2 18:13, Chunhai Guo wrote:
>> If userspace issues an fstrim with a range that does not include all
>> segments with small discards, these segments will be reused without being
> I didn't get it, if fstrim didn't cover those segments, why do we need to
> issue small discard for out-of-range segments?
Currently, all the dirty sentries in the dirty_sentries_bitmap are 
handled in the fstrim process regardless of whether they are within the 
fstrim range or not. Therefore, this patch is necessary to address the 
issue.

f2fs_flush_sit_entries()
     list_for_each_entry_safe(ses, tmp, head, set_list) {
         for_each_set_bit_from(segno, bitmap, end) {
             ...
             __clear_bit(segno, bitmap); // segno is cleared regardless 
of whether or not it is within the fstrim range
             ...
         }
     }


Thanks,

> Thanks,
>
>> discarded. This patch fixes this issue.
>> This patch is somewhat similar to commit 650d3c4e56e1 ("f2fs: fix a missing
>> discard prefree segments").
>>
>> Fixes: d7bc2484b8d4 ("f2fs: fix small discards not to issue redundantly")
>> Signed-off-by: Chunhai Guo <guochunhai@...o.com>
>> ---
>>    fs/f2fs/segment.c | 10 +++++++---
>>    1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 8fe9f794b581..af9a62591c49 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -4552,6 +4552,8 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>    	struct list_head *head = &SM_I(sbi)->sit_entry_set;
>>    	bool to_journal = !is_sbi_flag_set(sbi, SBI_IS_RESIZEFS);
>>    	struct seg_entry *se;
>> +	bool force = (cpc->reason & CP_DISCARD);
>> +	__u64 trim_start = cpc->trim_start;
>>    
>>    	down_write(&sit_i->sentry_lock);
>>    
>> @@ -4609,7 +4611,9 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>    #endif
>>    
>>    			/* add discard candidates */
>> -			if (!(cpc->reason & CP_DISCARD)) {
>> +			if (!force || (force &&
>> +					(segno < trim_start ||
>> +					 segno > cpc->trim_end))) {
>>    				cpc->trim_start = segno;
>>    				add_discard_addrs(sbi, cpc, false, false);
>>    			}
>> @@ -4649,8 +4653,8 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>    	f2fs_bug_on(sbi, !list_empty(head));
>>    	f2fs_bug_on(sbi, sit_i->dirty_sentries);
>>    out:
>> -	if (cpc->reason & CP_DISCARD) {
>> -		__u64 trim_start = cpc->trim_start;
>> +	if (force) {
>> +		cpc->trim_start = trim_start;
>>    
>>    		for (; cpc->trim_start <= cpc->trim_end; cpc->trim_start++)
>>    			add_discard_addrs(sbi, cpc, true, false);