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Date:   Thu, 26 Nov 2020 14:04:41 +0900
From:   Daeho Jeong <daeho43@...il.com>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE

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@...wei.com>님이 작성:
>
> On 2020/11/23 11:17, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@...gle.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@...gle.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.
> >

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