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From:   Daeho Jeong <daeho43@gmail.com>
Date:   Thu, 11 Jun 2020 20:04:06 +0900
Message-ID: <CACOAw_zyNFMYC3pTK3dT4yRgqp+-6yy3m2E64dkDkpNFKZicfQ@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: add F2FS_IOC_SEC_TRIM_FILE ioctl
To:     Chao Yu <yuchao0@huawei.com>
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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2020=EB=85=84 6=EC=9B=94 11=EC=9D=BC (=EB=AA=A9) =EC=98=A4=ED=9B=84 5:56, C=
hao Yu <yuchao0@huawei.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On 2020/6/11 11:16, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@google.com>
> >
> > Added a new ioctl to send discard commands or/and zero out
> > to whole data area of a regular file for security reason.
> >
> > Signed-off-by: Daeho Jeong <daehojeong@google.com>
> > ---
> >  fs/f2fs/f2fs.h |   8 +++
> >  fs/f2fs/file.c | 143 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 151 insertions(+)
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index c812fb8e2d9c..ca139fac5a73 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -434,6 +434,7 @@ static inline bool __has_cursum_space(struct f2fs_j=
ournal *journal,
> >                                       _IOR(F2FS_IOCTL_MAGIC, 18, __u64)
> >  #define F2FS_IOC_RESERVE_COMPRESS_BLOCKS                             \
> >                                       _IOR(F2FS_IOCTL_MAGIC, 19, __u64)
> > +#define F2FS_IOC_SEC_TRIM_FILE               _IOW(F2FS_IOCTL_MAGIC, 20=
, __u32)
> >
> >  #define F2FS_IOC_GET_VOLUME_NAME     FS_IOC_GETFSLABEL
> >  #define F2FS_IOC_SET_VOLUME_NAME     FS_IOC_SETFSLABEL
> > @@ -453,6 +454,13 @@ static inline bool __has_cursum_space(struct f2fs_=
journal *journal,
> >  #define F2FS_GOING_DOWN_METAFLUSH    0x3     /* going down with meta f=
lush */
> >  #define F2FS_GOING_DOWN_NEED_FSCK    0x4     /* going down to trigger =
fsck */
> >
> > +/*
> > + * Flags used by F2FS_IOC_SEC_TRIM_FILE
> > + */
> > +#define F2FS_TRIM_FILE_DISCARD               0x1     /* send discard c=
ommand */
> > +#define F2FS_TRIM_FILE_ZEROOUT               0x2     /* zero out */
> > +#define F2FS_TRIM_FILE_MASK          0x3
> > +
> >  #if defined(__KERNEL__) && defined(CONFIG_COMPAT)
> >  /*
> >   * ioctl commands in 32 bit emulation
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index dfa1ac2d751a..ba9b7ec5d6bf 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -3749,6 +3749,146 @@ static int f2fs_reserve_compress_blocks(struct =
file *filp, unsigned long arg)
> >       return ret;
> >  }
> >
> > +static int f2fs_secure_erase(struct block_device *bdev, block_t block,
> > +                                     block_t len, u32 flags)
> > +{
> > +     struct request_queue *q =3D bdev_get_queue(bdev);
> > +     sector_t sector =3D SECTOR_FROM_BLOCK(block);
> > +     sector_t nr_sects =3D SECTOR_FROM_BLOCK(len);
> > +     int ret =3D 0;
> > +
> > +     if (!q)
> > +             return -ENXIO;
> > +
> > +     if (flags & F2FS_TRIM_FILE_DISCARD)
> > +             ret =3D blkdev_issue_discard(bdev, sector, nr_sects, GFP_=
NOFS,
> > +                                             blk_queue_secure_erase(q)=
 ?
> > +                                             BLKDEV_DISCARD_SECURE : 0=
);
> > +
> > +     if (!ret && (flags & F2FS_TRIM_FILE_ZEROOUT))
> > +             ret =3D blkdev_issue_zeroout(bdev, sector, nr_sects, GFP_=
NOFS, 0);
> > +
> > +     return ret;
> > +}
> > +
> > +static int f2fs_sec_trim_file(struct file *filp, unsigned long arg)
> > +{
> > +     struct inode *inode =3D file_inode(filp);
> > +     struct f2fs_sb_info *sbi =3D F2FS_I_SB(inode);
> > +     struct address_space *mapping =3D inode->i_mapping;
> > +     struct block_device *prev_bdev =3D NULL;
> > +     pgoff_t index, pg_start =3D 0, pg_end;
> > +     block_t prev_block =3D 0, len =3D 0;
> > +     u32 flags;
> > +     int ret =3D 0;
> > +
> > +     if (!(filp->f_mode & FMODE_WRITE))
> > +             return -EBADF;
> > +
> > +     if (get_user(flags, (u32 __user *)arg))
> > +             return -EFAULT;
> > +     if (flags =3D=3D 0 || (flags & ~F2FS_TRIM_FILE_MASK))
> > +             return -EINVAL;
> > +
> > +     if ((flags & F2FS_TRIM_FILE_DISCARD) && !f2fs_hw_support_discard(=
sbi))
> > +             return -EOPNOTSUPP;
> > +
> > +     file_start_write(filp);
>
> Now, I'm a little confused about when we need to call __mnt_want_write_fi=
le(),
> you know, vfs_write() still will call this function when updating time.
> - __generic_file_write_iter
>  - file_update_time
>   - __mnt_want_write_file
>
> And previously, f2fs ioctl uses mnt_{want,drop}_write_file() whenever the=
re is
> any updates on fs/file, if Eric is correct, we need to clean up most of i=
octl
> interface as well.

I also saw most filesytem codes use just mnt_{want,drop}_write_file()
and actually it doesn't affect code working. It's a matter of doing a
redundant job or not.
AFAIUI, if the file is not open for writing (FMODE_WRITE), we have to
call mnt_want_write_file() to increase mnt_writers.
In this case, we already checked it has FMODE_WRITE flag.

>
> > +     inode_lock(inode);
> > +
> > +     if (!S_ISREG(inode->i_mode) || f2fs_is_atomic_file(inode) ||
> > +                     f2fs_compressed_file(inode)) {
> > +             ret =3D -EINVAL;
> > +             goto err;
> > +     }
> > +
> > +     if (!inode->i_size)
> > +             goto err;
> > +     pg_end =3D DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
> > +
> > +     ret =3D f2fs_convert_inline_inode(inode);
> > +     if (ret)
> > +             goto err;
> > +
> > +     down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> > +     down_write(&F2FS_I(inode)->i_mmap_sem);
> > +
> > +     ret =3D filemap_write_and_wait(mapping);
> > +     if (ret)
> > +             goto out;
> > +
> > +     truncate_inode_pages(mapping, 0);
> > +
> > +     for (index =3D pg_start; index < pg_end;) {
> > +             struct dnode_of_data dn;
> > +             unsigned int end_offset;
> > +
> > +             set_new_dnode(&dn, inode, NULL, NULL, 0);
> > +             ret =3D f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
> > +             if (ret)
>
> if (ret =3D=3D -ENOENT) {
>         index =3D f2fs_get_next_page_offset(&dn, index);
>         continue;
> }

Got it.

>
> > +                     goto out;
> > +
> > +             end_offset =3D ADDRS_PER_PAGE(dn.node_page, inode);
> > +             if (pg_end < end_offset + index)
> > +                     end_offset =3D pg_end - index;
> > +
> > +             for (; dn.ofs_in_node < end_offset;
> > +                             dn.ofs_in_node++, index++) {
> > +                     struct block_device *cur_bdev;
> > +                     block_t blkaddr =3D f2fs_data_blkaddr(&dn);
> > +
> > +                     if (__is_valid_data_blkaddr(blkaddr)) {
> > +                             if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inod=
e),
> > +                                     blkaddr, DATA_GENERIC_ENHANCE)) {
> > +                                     ret =3D -EFSCORRUPTED;
> > +                                     goto out;
>
>
> if we goto out label here, we will miss to call f2fs_put_dnode()?
>

Oops, I missed this, when I changed the code flow. Thanks!

> > +                             }
> > +                     } else
>
> How about this?
>
> if (!__is_valid_data_blkaddr())
>         continue;
>
> if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), blkaddr, DATA_GENERIC_ENHANC=
E)) {
>         ret =3D -EFSCORRUPTED;
>         goto out;
> }
>

Looks better.

> > +                             continue;
> > +
> > +                     cur_bdev =3D f2fs_target_device(sbi, blkaddr, NUL=
L);
> > +                     if (f2fs_is_multi_device(sbi)) {
> > +                             int i =3D f2fs_target_device_index(sbi, b=
lkaddr);
> > +
> > +                             blkaddr -=3D FDEV(i).start_blk;
> > +                     }
> > +
> > +                     if (len) {
> > +                             if (prev_bdev =3D=3D cur_bdev &&
> > +                                     blkaddr =3D=3D prev_block + len) =
{
> > +                                     len++;
> > +                             } else {
> > +                                     ret =3D f2fs_secure_erase(prev_bd=
ev,
> > +                                                     prev_block, len, =
flags);
> > +                                     if (ret)
> > +                                             goto out;
>
> Ditto,

Got it.