linux-kernel - Re: [f2fs-dev] [PATCH v3 3/6] f2fs: compress: fix to check unreleased compressed cluster

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Date: Fri, 12 Jan 2024 09:06:39 +0800
From: Chao Yu <chao@...nel.org>
To: Daeho Jeong <daeho43@...il.com>
Cc: jaegeuk@...nel.org, linux-kernel@...r.kernel.org,
 linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v3 3/6] f2fs: compress: fix to check unreleased
 compressed cluster

On 2024/1/12 1:15, Daeho Jeong wrote:
> On Wed, Jan 10, 2024 at 5:33 PM Chao Yu <chao@...nel.org> wrote:
>>
>> On 2024/1/11 9:18, Daeho Jeong wrote:
>>> On Thu, Dec 28, 2023 at 6:33 AM Chao Yu <chao@...nel.org> wrote:
>>>>
>>>> From: Sheng Yong <shengyong@...o.com>
>>>>
>>>> Compressed cluster may not be released due to we can fail in
>>>> release_compress_blocks(), fix to handle reserved compressed
>>>> cluster correctly in reserve_compress_blocks().
>>>>
>>>> Fixes: 4c8ff7095bef ("f2fs: support data compression")
>>>> Signed-off-by: Sheng Yong <shengyong@...o.com>
>>>> Signed-off-by: Chao Yu <chao@...nel.org>
>>>> ---
>>>>    fs/f2fs/file.c | 12 ++++++++++++
>>>>    1 file changed, 12 insertions(+)
>>>>
>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>> index 026d05a7edd8..782ae3be48f6 100644
>>>> --- a/fs/f2fs/file.c
>>>> +++ b/fs/f2fs/file.c
>>>> @@ -3624,6 +3624,15 @@ static int reserve_compress_blocks(struct dnode_of_data *dn, pgoff_t count)
>>>>                                   goto next;
>>>>                           }
>>>>
>>>> +                       /*
>>>> +                        * compressed cluster was not released due to
>>>> +                        * it fails in release_compress_blocks().
>>>> +                        */
>>>> +                       if (blkaddr == NEW_ADDR) {
>>>> +                               compr_blocks++;
>>>> +                               continue;
>>>> +                       }
>>>> +
>>>>                           if (__is_valid_data_blkaddr(blkaddr)) {
>>>>                                   compr_blocks++;
>>>>                                   continue;
>>>
>>> How about merging two conditions like "blkaddr == NEW_ADDR ||
>>> __is_valid_data_blkaddr(blkaddr)"?
>>
>> Oh, sure.
>>
>>>
>>>> @@ -3633,6 +3642,9 @@ static int reserve_compress_blocks(struct dnode_of_data *dn, pgoff_t count)
>>>>                   }
>>>>
>>>>                   reserved = cluster_size - compr_blocks;
>>>> +               if (!reserved)
>>>> +                       goto next;
>>>> +
>>>
>>> How can the reserved variable be zero?
>>
>> I guess it can happen if a cluster was not released during
>> release_compress_blocks(), then all blocks in the cluster should
>> has been reserved, so, in this round of reserving, it needs to skip
>> reserve blocks, right?
> 
> Let's assume cluster_size is 4. How can compr_blocks be 4?
> 
>                          if (i == 0) {
>                                  if (blkaddr == COMPRESS_ADDR)
>                                          continue;
>                                  dn->ofs_in_node += cluster_size;
>                                  goto next;
>                          }
> 
> We skip the block having COMPRESS_ADDR when counting compr_blocks.
> So, the maximum value of compr_blocks should be 3, right?

Ah, got it, and I think you're right.

Should fix the condition as below?

		/* for the case all blocks in cluster were reserved */
		if (reserved == 1)
			goto next;

Thanks,

> 
>>
>> Thanks,
>>
>>>
>>>>                   ret = inc_valid_block_count(sbi, dn->inode, &reserved);
>>>>                   if (ret)
>>>>                           return ret;
>>>> --
>>>> 2.40.1
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Linux-f2fs-devel mailing list
>>>> Linux-f2fs-devel@...ts.sourceforge.net
>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel