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From:   Daeho Jeong <daeho43@gmail.com>
Date:   Mon, 31 Aug 2020 08:36:51 +0900
Message-ID: <CACOAw_xnTh9mVO7b+inK_Gsk+g+88W7p5GmLhJV3XY8UHssLzw@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: make fibmap consistent with fiemap for
 compression chunk
To:     Chao Yu <chao@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com,
        Daeho Jeong <daehojeong@google.com>
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I got it. Thanks~ :)

2020=EB=85=84 8=EC=9B=94 30=EC=9D=BC (=EC=9D=BC) =EC=98=A4=EC=A0=84 8:44, C=
hao Yu <chao@kernel.org>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On 2020-8-28 11:49, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@google.com>
> >
> > Currently fibmap returns zero address for compression chunk. But it
> > is not consistent with the output of fiemap, since fiemap returns
> > real pysical block address related to the compression chunk. Therefore
> > I suggest fibmap returns the same output with fiemap.
>
> We can return real physical block address in fiemap, because we have set
> FIEMAP_EXTENT_ENCODED flag in extent.fe_flags, then user can be noticed t=
hat he
> can not just read/write that block address for access/update in-there dat=
a.
>
> Quoted from Documentation/filesystems/fiemap.rst
> "
> FIEMAP_EXTENT_ENCODED
>    This extent does not consist of plain filesystem blocks but is
>    encoded (e.g. encrypted or compressed).  Reading the data in this
>    extent via I/O to the block device will have undefined results.
> "
>
> However, there is no such flag in fibmap interface, so I just return bloc=
k
> address for those logical pages in non-compressed cluster.
>
> Thanks,
>
> >
> > Signed-off-by: Daeho Jeong <daehojeong@google.com>
> > ---
> >  fs/f2fs/data.c | 33 ---------------------------------
> >  1 file changed, 33 deletions(-)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index c1b676be67b9..8c26c5d0c778 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -3708,36 +3708,6 @@ static int f2fs_set_data_page_dirty(struct page =
*page)
> >       return 0;
> >  }
> >
> > -
> > -static sector_t f2fs_bmap_compress(struct inode *inode, sector_t block=
)
> > -{
> > -#ifdef CONFIG_F2FS_FS_COMPRESSION
> > -     struct dnode_of_data dn;
> > -     sector_t start_idx, blknr =3D 0;
> > -     int ret;
> > -
> > -     start_idx =3D round_down(block, F2FS_I(inode)->i_cluster_size);
> > -
> > -     set_new_dnode(&dn, inode, NULL, NULL, 0);
> > -     ret =3D f2fs_get_dnode_of_data(&dn, start_idx, LOOKUP_NODE);
> > -     if (ret)
> > -             return 0;
> > -
> > -     if (dn.data_blkaddr !=3D COMPRESS_ADDR) {
> > -             dn.ofs_in_node +=3D block - start_idx;
> > -             blknr =3D f2fs_data_blkaddr(&dn);
> > -             if (!__is_valid_data_blkaddr(blknr))
> > -                     blknr =3D 0;
> > -     }
> > -
> > -     f2fs_put_dnode(&dn);
> > -     return blknr;
> > -#else
> > -     return 0;
> > -#endif
> > -}
> > -
> > -
> >  static sector_t f2fs_bmap(struct address_space *mapping, sector_t bloc=
k)
> >  {
> >       struct inode *inode =3D mapping->host;
> > @@ -3753,9 +3723,6 @@ static sector_t f2fs_bmap(struct address_space *m=
apping, sector_t block)
> >       if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
> >               filemap_write_and_wait(mapping);
> >
> > -     if (f2fs_compressed_file(inode))
> > -             blknr =3D f2fs_bmap_compress(inode, block);
> > -
> >       if (!get_data_block_bmap(inode, block, &tmp, 0))
> >               blknr =3D tmp.b_blocknr;
> >  out:
> >