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Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: add F2FS_IOC_DECOMPRESS_FILE and
 F2FS_IOC_COMPRESS_FILE
To:     Daeho Jeong <daeho43@gmail.com>
CC:     <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <kernel-team@android.com>, Daeho Jeong <daehojeong@google.com>
References: <20201123031751.36811-1-daeho43@gmail.com>
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 <5b3cb83d-5d0f-c1ca-2cff-f28372dec48e@huawei.com>
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 <CACOAw_yRD5uQiZLXj2X_MjamCQSK+WHRDuvdvVeEeAFJqDpbMw@mail.gmail.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <065e47fd-29f1-edef-c40d-d392b1a59081@huawei.com>
Date:   Thu, 26 Nov 2020 14:54:05 +0800
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Daeho,

On 2020/11/26 14:35, Daeho Jeong wrote:
> Chao,
> 
>> A little bit wired, why not failing cluster_may_compress() for user mode, and
>> let writepages write cluster as raw blocks, in-where we can update i_compr_blocks
>> and global compr block stats correctly.
> 
> For decompression ioctl, I've made f2fs_need_compress_data() return
> "false" to prevent compression write, so we don't use
> f2fs_write_compressed_pages() anymore in this case.
> Because of this, I manually updated i_compr_blocks. Do you have any
> suggestions on this?

I meant, we can control condition to call into below stack, then i_compr_blocks
can be updated correctly.

- f2fs_ioc_decompress_file
  - writepages
   - f2fs_write_multi_pages
    - cluster_may_compress   return false when ioc_decompress is in-process.
     - f2fs_write_raw_pages
      - f2fs_do_write_data_page
       - f2fs_i_compr_blocks_update

Thanks,

> 
> 2020년 11월 26일 (목) 오후 2:04, Daeho Jeong <daeho43@gmail.com>님이 작성:
>>
>> Eric,
>>
>> do_page_cache_ra() is defined in mm/internal.h for internal use
>> between in mm, so we cannot use this one right now.
>> So, I think we could use page_cache_ra_unbounded(), because we already
>> check i_size boundary on our own.
>> What do you think?
>>
>> 2020년 11월 24일 (화) 오후 12:05, Chao Yu <yuchao0@huawei.com>님이 작성:
>>>
>>> On 2020/11/23 11:17, Daeho Jeong wrote:
>>>> From: Daeho Jeong <daehojeong@google.com>
>>>>
>>>> Added two ioctl to decompress/compress explicitly the compression
>>>> enabled file in "compress_mode=user-based" mount option.
>>>>
>>>> Using these two ioctls, the users can make a control of compression
>>>> and decompression of their files.
>>>>
>>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>>> ---
>>>>    fs/f2fs/file.c            | 181 +++++++++++++++++++++++++++++++++++++-
>>>>    include/uapi/linux/f2fs.h |   2 +
>>>>    2 files changed, 182 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>> index be8db06aca27..e8f142470e87 100644
>>>> --- a/fs/f2fs/file.c
>>>> +++ b/fs/f2fs/file.c
>>>> @@ -4026,6 +4026,180 @@ static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
>>>>        return ret;
>>>>    }
>>>>
>>>> +static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
>>>> +{
>>>> +     DEFINE_READAHEAD(ractl, NULL, inode->i_mapping, page_idx);
>>>> +     struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>> +     struct address_space *mapping = inode->i_mapping;
>>>> +     struct page *page;
>>>> +     pgoff_t redirty_idx = page_idx;
>>>> +     int i, page_len = 0, ret = 0;
>>>> +
>>>> +     page_cache_ra_unbounded(&ractl, len, 0);
>>>> +
>>>> +     for (i = 0; i < len; i++, page_idx++) {
>>>> +             page = read_cache_page(mapping, page_idx, NULL, NULL);
>>>> +             if (IS_ERR(page)) {
>>>> +                     ret = PTR_ERR(page);
>>>> +                     f2fs_warn(sbi, "%s: inode (%lu) : page_index (%lu) "
>>>> +                             "couldn't be read (errno:%d).\n",
>>>> +                             __func__, inode->i_ino, page_idx, ret);
>>>
>>> This is a common error case during calling read_cache_page(), IMO, this looks
>>> more like a debug log, so I prefer to print nothing here, or at least using
>>> f2fs_debug() instead.
>>>
>>>> +                     break;
>>>> +             }
>>>> +             page_len++;
>>>> +     }
>>>> +
>>>> +     for (i = 0; i < page_len; i++, redirty_idx++) {
>>>> +             page = find_lock_page(mapping, redirty_idx);
>>>> +             if (!page) {
>>>> +                     ret = -ENOENT;
>>>> +                     f2fs_warn(sbi, "%s: inode (%lu) : page_index (%lu) "
>>>> +                             "couldn't be found (errno:%d).\n",
>>>> +                             __func__, inode->i_ino, redirty_idx, ret);
>>>
>>> Ditto.
>>>
>>>> +             }
>>>> +             set_page_dirty(page);
>>>> +             f2fs_put_page(page, 1);
>>>> +             f2fs_put_page(page, 0);
>>>> +     }
>>>> +
>>>> +     return ret;
>>>> +}
>>>> +
>>>> +static int f2fs_ioc_decompress_file(struct file *filp, unsigned long arg)
>>>> +{
>>>> +     struct inode *inode = file_inode(filp);
>>>> +     struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>> +     struct f2fs_inode_info *fi = F2FS_I(inode);
>>>> +     pgoff_t page_idx = 0, last_idx;
>>>> +     int cluster_size = F2FS_I(inode)->i_cluster_size;
>>>> +     int count, ret;
>>>> +
>>>> +     if (!f2fs_sb_has_compression(sbi))
>>>> +             return -EOPNOTSUPP;
>>>> +
>>>> +     if (!(filp->f_mode & FMODE_WRITE))
>>>> +             return -EBADF;
>>>> +
>>>> +     if (!f2fs_compressed_file(inode))
>>>> +             return -EINVAL;
>>>
>>> Before compressubg/decompressing file, should we check whether current inode's
>>> compress algorithm backend is available in f2fs module?
>>>
>>>> +
>>>> +     f2fs_balance_fs(F2FS_I_SB(inode), true);
>>>> +
>>>> +     file_start_write(filp);
>>>> +     inode_lock(inode);
>>>> +
>>>> +     if (f2fs_is_mmap_file(inode)) {
>>>> +             ret = -EBUSY;
>>>> +             goto out;
>>>> +     }
>>>> +
>>>> +     ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
>>>> +     if (ret)
>>>> +             goto out;
>>>> +
>>>> +     if (!atomic_read(&fi->i_compr_blocks))
>>>> +             goto out;
>>>> +
>>>> +     last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
>>>> +
>>>> +     count = last_idx - page_idx;
>>>> +     while (count) {
>>>> +             int len = min(cluster_size, count);
>>>> +
>>>> +             ret = redirty_blocks(inode, page_idx, len);
>>>> +
>>>
>>> unneeded blank line..
>>>
>>>> +             if (ret < 0)
>>>> +                     break;
>>>> +
>>>> +             page_idx += len;
>>>> +             count -= len;
>>>
>>> Considering there isn't so many memory in low-end device, how about calling
>>> filemap_fdatawrite() to writeback cluster after redirty several clusters
>>> or xxMB?
>>>
>>>> +     }
>>>> +
>>>> +     if (!ret)
>>>> +             ret = filemap_write_and_wait_range(inode->i_mapping, 0,
>>>> +                                                     LLONG_MAX);
>>>> +
>>>> +     if (!ret) {
>>>> +             stat_sub_compr_blocks(inode, atomic_read(&fi->i_compr_blocks));
>>>> +             atomic_set(&fi->i_compr_blocks, 0);
>>>> +             f2fs_mark_inode_dirty_sync(inode, true);
>>>
>>> A little bit wired, why not failing cluster_may_compress() for user mode, and
>>> let writepages write cluster as raw blocks, in-where we can update i_compr_blocks
>>> and global compr block stats correctly.
>>>
>>>> +     } else {
>>>> +             f2fs_warn(sbi, "%s: The file might be partially decompressed "
>>>> +                             "(errno=%d). Please delete the file.\n",
>>>> +                             __func__, ret);
>>>> +     }
>>>> +out:
>>>> +     inode_unlock(inode);
>>>> +     file_end_write(filp);
>>>> +
>>>> +     return ret;
>>>> +}
>>>> +
>>>> +static int f2fs_ioc_compress_file(struct file *filp, unsigned long arg)
>>>> +{
>>>> +     struct inode *inode = file_inode(filp);
>>>> +     struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>> +     pgoff_t page_idx = 0, last_idx;
>>>> +     int cluster_size = F2FS_I(inode)->i_cluster_size;
>>>> +     int count, ret;
>>>> +
>>>> +     if (!f2fs_sb_has_compression(sbi))
>>>> +             return -EOPNOTSUPP;
>>>> +
>>>> +     if (!(filp->f_mode & FMODE_WRITE))
>>>> +             return -EBADF;
>>>> +
>>>> +     if (!f2fs_compressed_file(inode))
>>>> +             return -EINVAL;
>>>
>>> algorithm backend check?
>>>
>>>> +
>>>> +     f2fs_balance_fs(F2FS_I_SB(inode), true);
>>>> +
>>>> +     file_start_write(filp);
>>>> +     inode_lock(inode);
>>>> +
>>>> +     if (f2fs_is_mmap_file(inode)) {
>>>> +             ret = -EBUSY;
>>>> +             goto out;
>>>> +     }
>>>> +
>>>> +     ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
>>>> +     if (ret)
>>>> +             goto out;
>>>> +
>>>> +     set_inode_flag(inode, FI_ENABLE_COMPRESS);
>>>> +
>>>> +     last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
>>>> +
>>>> +     count = last_idx - page_idx;
>>>> +     while (count) {
>>>> +             int len = min(cluster_size, count);
>>>> +
>>>> +             ret = redirty_blocks(inode, page_idx, len);
>>>> +
>>>
>>> Ditto.
>>>
>>> Thanks,
>>>
>>>> +             if (ret < 0)
>>>> +                     break;
>>>> +
>>>> +             page_idx += len;
>>>> +             count -= len;
>>>> +     }
>>>> +
>>>> +     if (!ret)
>>>> +             ret = filemap_write_and_wait_range(inode->i_mapping, 0,
>>>> +                                                     LLONG_MAX);
>>>> +
>>>> +     clear_inode_flag(inode, FI_ENABLE_COMPRESS);
>>>> +
>>>> +     if (ret)
>>>> +             f2fs_warn(sbi, "%s: The file might be partially compressed "
>>>> +                             "(errno=%d). Please delete the file.\n",
>>>> +                             __func__, ret);
>>>> +out:
>>>> +     inode_unlock(inode);
>>>> +     file_end_write(filp);
>>>> +
>>>> +     return ret;
>>>> +}
>>>> +
>>>>    static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>>>>    {
>>>>        switch (cmd) {
>>>> @@ -4113,6 +4287,10 @@ static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>>>>                return f2fs_ioc_get_compress_option(filp, arg);
>>>>        case F2FS_IOC_SET_COMPRESS_OPTION:
>>>>                return f2fs_ioc_set_compress_option(filp, arg);
>>>> +     case F2FS_IOC_DECOMPRESS_FILE:
>>>> +             return f2fs_ioc_decompress_file(filp, arg);
>>>> +     case F2FS_IOC_COMPRESS_FILE:
>>>> +             return f2fs_ioc_compress_file(filp, arg);
>>>>        default:
>>>>                return -ENOTTY;
>>>>        }
>>>> @@ -4352,7 +4530,8 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>>>>        case F2FS_IOC_SEC_TRIM_FILE:
>>>>        case F2FS_IOC_GET_COMPRESS_OPTION:
>>>>        case F2FS_IOC_SET_COMPRESS_OPTION:
>>>> -             break;
>>>> +     case F2FS_IOC_DECOMPRESS_FILE:
>>>> +     case F2FS_IOC_COMPRESS_FILE:
>>>>        default:
>>>>                return -ENOIOCTLCMD;
>>>>        }
>>>> diff --git a/include/uapi/linux/f2fs.h b/include/uapi/linux/f2fs.h
>>>> index f00199a2e38b..352a822d4370 100644
>>>> --- a/include/uapi/linux/f2fs.h
>>>> +++ b/include/uapi/linux/f2fs.h
>>>> @@ -40,6 +40,8 @@
>>>>                                                struct f2fs_comp_option)
>>>>    #define F2FS_IOC_SET_COMPRESS_OPTION        _IOW(F2FS_IOCTL_MAGIC, 22,      \
>>>>                                                struct f2fs_comp_option)
>>>> +#define F2FS_IOC_DECOMPRESS_FILE     _IO(F2FS_IOCTL_MAGIC, 23)
>>>> +#define F2FS_IOC_COMPRESS_FILE               _IO(F2FS_IOCTL_MAGIC, 24)
>>>>
>>>>    /*
>>>>     * should be same as XFS_IOC_GOINGDOWN.
>>>>
> .
>