linux-ext4 - Re: [PATCH V3 5/5] ext4: make fallocate retry when err is ENOSPC

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Date:   Mon, 26 Jul 2021 15:05:41 +0800
From:   Wang Jianchao <jianchao.wan9@...il.com>
To:     Guoqing Jiang <guoqing.jiang@...ux.dev>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     tytso@....edu, adilger.kernel@...ger.ca
Subject: Re: [PATCH V3 5/5] ext4: make fallocate retry when err is ENOSPC



On 2021/7/26 11:40 AM, Guoqing Jiang wrote:
> Hi,
> 
> On 7/24/21 3:41 PM, Wang Jianchao wrote:
>> From: Wang Jianchao <wangjianchao@...ishou.com>
>>
>> The blocks may be waiting for journal commit to be freed back to
>> mb buddy. Let fallocate wait and retry in that case.
>>
>> Signed-off-by: Wang Jianchao <wangjianchao@...ishou.com>
>> ---
>>   fs/ext4/extents.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 92ad64b89d9b..ad0b874d3448 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -4635,7 +4635,7 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>>       struct inode *inode = file_inode(file);
>>       loff_t new_size = 0;
>>       unsigned int max_blocks;
>> -    int ret = 0;
>> +    int ret = 0, retries = 0;
>>       int flags;
>>       ext4_lblk_t lblk;
>>       unsigned int blkbits = inode->i_blkbits;
>> @@ -4656,6 +4656,7 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>>                FALLOC_FL_INSERT_RANGE))
>>           return -EOPNOTSUPP;
>>   +retry:
>>       ext4_fc_start_update(inode);
>>         if (mode & FALLOC_FL_PUNCH_HOLE) {
>> @@ -4722,6 +4723,9 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>>       trace_ext4_fallocate_exit(inode, offset, max_blocks, ret);
>>   exit:
>>       ext4_fc_stop_update(inode);
>> +    if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
>> +        goto retry;
>> +
> 
> Not sure if it is necessary since ext4_alloc_file_blocks already retries allocate.

Yes, this patch should be get rid of.
But it is indeed helpful to fix the xfstest generic/371 which does concurrently write/rm
and fallocate/rm. I'll figure out some other way to improve that

Thanks
Jianchao

> 
> Thanks,
> Guoqing