Re: [f2fs-dev] [PATCH] f2fs: compress: don't force buffered io when in COMPR_MODE_USER mode

[Chao Yu <chao@kernel.org>]

On 2023/6/19 17:31, Yangtao Li wrote:
> On 2023/6/19 12:04, Chao Yu wrote:
> 
>> On 2023/6/19 11:11, Yangtao Li wrote:
>>> On 2023/6/19 8:54, Chao Yu wrote:
>>>
>>>> On 2023/6/13 12:14, Yangtao Li wrote:
>>>>>
>>>>> On 2023/6/12 22:38, Chao Yu wrote:
>>>>>> On 2023/6/9 21:15, Yangtao Li wrote:
>>>>>>> It is observed that when in user compression mode
>>>>>>> (compress_extension=*),
>>>>>>> even though the file is not compressed, the file is still forced
>>>>>>> to use
>>>>>>> buffer io, which makes the AndroBench sequential read and write drop
>>>>>>> significantly. In fact, when the file is not compressed, we don't
>>>>>>> need
>>>>>>> to force it to buffer io.
>>>>>>>
>>>>>>>                     | w/o patch | w/ patch |
>>>>>>> seq read  (MB/s) | 1320.068  | 3696.154 |
>>>>>>> seq write (MB/s) | 617.996   | 2978.478 |
>>>>>>>
>>>>>>> Fixes: 4c8ff7095bef ("f2fs: support data compression")
>>>>>>> Signed-off-by: Qi Han <hanqi@vivo.com>
>>>>>>> Signed-off-by: Yangtao Li <frank.li@vivo.com>
>>>>>>> ---
>>>>>>>     fs/f2fs/f2fs.h | 14 ++++++++++++++
>>>>>>>     fs/f2fs/file.c |  2 +-
>>>>>>>     2 files changed, 15 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>> index 1efcfd9e5a99..7f5472525310 100644
>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>> @@ -3168,6 +3168,20 @@ static inline int f2fs_compressed_file(struct
>>>>>>> inode *inode)
>>>>>>>             is_inode_flag_set(inode, FI_COMPRESSED_FILE);
>>>>>>>     }
>>>>>>>     +static inline bool f2fs_is_compressed_file(struct inode *inode)
>>>>>>> +{
>>>>>>> +    int compress_mode =
>>>>>>> F2FS_OPTION(F2FS_I_SB(inode)).compress_mode;
>>>>>>> +
>>>>>>> +    if (compress_mode == COMPR_MODE_FS)
>>>>>>> +        return f2fs_compressed_file(inode);
>>>>>>> +    else if (atomic_read(&F2FS_I(inode)->i_compr_blocks) ||
>>>>>>
>>>>>> Should check dirty page as well? i_compr_blocks may increase after
>>>>>> data writeback.
>>>>>>
>>>>> IIUC, in COMPR_MODE_USER mode, i_compr_blocks will only be updated
>>>>> when
>>>>> FI_ENABLE_COMPRESS is enabled.
>>>>>
>>>>> If FI_ENABLE_COMPRESS is not enabled, i_compr_blocks will never be
>>>>> updated after data writeback.
>>>>>
>>>>> So there is no need to additionally judge whether there is a dirty
>>>>> page?
>>>>
>>>> Oh, user mode, that's correct.
>>>>
>>>> If we allow dio/aio on compress file, it needs to consider race case in
>>>> between aio and ioc_compress_file.
>>>
>>>
>>> The inode_lock is already held in f2fs_file_write_iter and
>>> f2fs_ioc_compress_file, I guess this is enough?
>>>
>>> What else?
>>
>> aio may complete outside inode lock, so it needs to call inode_dio_wait()
>> in f2fs_ioc_compress_file() to avoid the race case?
> 
> 
> How about adding this below？
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index f45d05c13ae5..5021d13e788b 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -4146,6 +4146,10 @@ static int f2fs_ioc_compress_file(struct file *filp)
>                   goto out;
>           }
> 
> +       /* avoid race case between aio and ioc_compress_file */
> +       if (F2FS_OPTION(sbi).compress_mode == COMPR_MODE_USER)

f2fs_ioc_compress_file() has already checked the mode?

Thanks,

> +               inode_dio_wait(inode);
> +
>           ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
>           if (ret)
>                   goto out;
> 
> 
> Thanks,
> 
> 
>>
>> Thanks,
>>
>>>
>>>
>>> 4691 static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct
>>> iov_iter *from)
>>> 4692 {
>>> 4693         struct inode *inode = file_inode(iocb->ki_filp);
>>> 4694         const loff_t orig_pos = iocb->ki_pos;
>>> 4695         const size_t orig_count = iov_iter_count(from);
>>> 4696         loff_t target_size;
>>> 4697         bool dio;
>>> 4698         bool may_need_sync = true;
>>> 4699         int preallocated;
>>> 4700         ssize_t ret;
>>> 4701
>>> 4702         if (unlikely(f2fs_cp_error(F2FS_I_SB(inode)))) {
>>> 4703                 ret = -EIO;
>>> 4704                 goto out;
>>> 4705         }
>>> 4706
>>> 4707         if (!f2fs_is_compress_backend_ready(inode)) {
>>> 4708                 ret = -EOPNOTSUPP;
>>> 4709                 goto out;
>>> 4710         }
>>> 4711
>>> 4712         if (iocb->ki_flags & IOCB_NOWAIT) {
>>> 4713                 if (!inode_trylock(inode)) {
>>> 4714                         ret = -EAGAIN;
>>> 4715                         goto out;
>>> 4716                 }
>>> 4717         } else {
>>> 4718                 inode_lock(inode);
>>> 4719         }
>>>
>>>
>>> 4115 static int f2fs_ioc_compress_file(struct file *filp)
>>> 4116 {
>>> 4117         struct inode *inode = file_inode(filp);
>>> 4118         struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>> 4119         pgoff_t page_idx = 0, last_idx;
>>> 4120         unsigned int blk_per_seg = sbi->blocks_per_seg;
>>> 4121         int cluster_size = F2FS_I(inode)->i_cluster_size;
>>> 4122         int count, ret;
>>> 4123
>>> 4124         if (!f2fs_sb_has_compression(sbi) ||
>>> 4125                         F2FS_OPTION(sbi).compress_mode !=
>>> COMPR_MODE_USER)
>>> 4126                 return -EOPNOTSUPP;
>>> 4127
>>> 4128         if (!(filp->f_mode & FMODE_WRITE))
>>> 4129                 return -EBADF;
>>> 4130
>>> 4131         if (!f2fs_compressed_file(inode))
>>> 4132                 return -EINVAL;
>>> 4133
>>> 4134         f2fs_balance_fs(sbi, true);
>>> 4135
>>> 4136         file_start_write(filp);
>>> 4137         inode_lock(inode);
>>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>> +        is_inode_flag_set(inode, FI_COMPRESS_RELEASED) ||
>>>>>>> +        is_inode_flag_set(inode, FI_ENABLE_COMPRESS))
>>>>>>> +        return true;
>>>>>>> +
>>>>>>> +    return false;
>>>>>>> +}
>>>>>>> +
>>>>>>>     static inline bool f2fs_need_compress_data(struct inode *inode)
>>>>>>>     {
>>>>>>>         int compress_mode =
>>>>>>> F2FS_OPTION(F2FS_I_SB(inode)).compress_mode;
>>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>>>> index 74ecc9e20619..0698129b2165 100644
>>>>>>> --- a/fs/f2fs/file.c
>>>>>>> +++ b/fs/f2fs/file.c
>>>>>>> @@ -821,7 +821,7 @@ static bool f2fs_force_buffered_io(struct inode
>>>>>>> *inode, int rw)
>>>>>>>             return true;
>>>>>>>         if (fsverity_active(inode))
>>>>>>>             return true;
>>>>>>> -    if (f2fs_compressed_file(inode))
>>>>>>> +    if (f2fs_is_compressed_file(inode))
>>>>>>>             return true;
>>>>>>>           /* disallow direct IO if any of devices has unaligned
>>>>>>> blksize */


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