Re: [f2fs-dev] [PATCH] f2fs: fix to add swap extent correctly

[Ju Hyung Park]

Hi Chao,

I think this should be sent to linux-stable.
Thoughts?

Thanks.

On Fri, Dec 27, 2019 at 7:45 PM Chao Yu <yuchao0@xxxxxxxxxx> wrote:
>
> As Youling reported in mailing list:
>
> https://www.linuxquestions.org/questions/linux-newbie-8/the-file-system-f2fs-is-broken-4175666043/
>
> https://www.linux.org/threads/the-file-system-f2fs-is-broken.26490/
>
> There is a test case can corrupt f2fs image:
> - dd if=/dev/zero of=/swapfile bs=1M count=4096
> - chmod 600 /swapfile
> - mkswap /swapfile
> - swapon --discard /swapfile
>
> The root cause is f2fs_swap_activate() intends to return zero value
> to setup_swap_extents() to enable SWP_FS mode (swap file goes through
> fs), in this flow, setup_swap_extents() setups swap extent with wrong
> block address range, result in discard_swap() erasing incorrect address.
>
> Because f2fs_swap_activate() has pinned swapfile, its data block
> address will not change, it's safe to let swap to handle IO through
> raw device, so we can get rid of SWAP_FS mode and initial swap extents
> inside f2fs_swap_activate(), by this way, later discard_swap() can trim
> in right address range.
>
> Fixes: 4969c06a0d83 ("f2fs: support swap file w/ DIO")
> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> ---
>  fs/f2fs/data.c | 32 +++++++++++++++++++++++++-------
>  1 file changed, 25 insertions(+), 7 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 19cd03450066..ee4d3d284379 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3608,7 +3608,8 @@ int f2fs_migrate_page(struct address_space *mapping,
>
>  #ifdef CONFIG_SWAP
>  /* Copied from generic_swapfile_activate() to check any holes */
> -static int check_swap_activate(struct file *swap_file, unsigned int max)
> +static int check_swap_activate(struct swap_info_struct *sis,
> +                               struct file *swap_file, sector_t *span)
>  {
>         struct address_space *mapping = swap_file->f_mapping;
>         struct inode *inode = mapping->host;
> @@ -3619,6 +3620,8 @@ static int check_swap_activate(struct file *swap_file, unsigned int max)
>         sector_t last_block;
>         sector_t lowest_block = -1;
>         sector_t highest_block = 0;
> +       int nr_extents = 0;
> +       int ret;
>
>         blkbits = inode->i_blkbits;
>         blocks_per_page = PAGE_SIZE >> blkbits;
> @@ -3630,7 +3633,8 @@ static int check_swap_activate(struct file *swap_file, unsigned int max)
>         probe_block = 0;
>         page_no = 0;
>         last_block = i_size_read(inode) >> blkbits;
> -       while ((probe_block + blocks_per_page) <= last_block && page_no < max) {
> +       while ((probe_block + blocks_per_page) <= last_block &&
> +                       page_no < sis->max) {
>                 unsigned block_in_page;
>                 sector_t first_block;
>
> @@ -3670,13 +3674,27 @@ static int check_swap_activate(struct file *swap_file, unsigned int max)
>                                 highest_block = first_block;
>                 }
>
> +               /*
> +                * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
> +                */
> +               ret = add_swap_extent(sis, page_no, 1, first_block);
> +               if (ret < 0)
> +                       goto out;
> +               nr_extents += ret;
>                 page_no++;
>                 probe_block += blocks_per_page;
>  reprobe:
>                 continue;
>         }
> -       return 0;
> -
> +       ret = nr_extents;
> +       *span = 1 + highest_block - lowest_block;
> +       if (page_no == 0)
> +               page_no = 1;    /* force Empty message */
> +       sis->max = page_no;
> +       sis->pages = page_no - 1;
> +       sis->highest_bit = page_no - 1;
> +out:
> +       return ret;
>  bad_bmap:
>         pr_err("swapon: swapfile has holes\n");
>         return -EINVAL;
> @@ -3701,14 +3719,14 @@ static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
>         if (f2fs_disable_compressed_file(inode))
>                 return -EINVAL;
>
> -       ret = check_swap_activate(file, sis->max);
> -       if (ret)
> +       ret = check_swap_activate(sis, file, span);
> +       if (ret < 0)
>                 return ret;
>
>         set_inode_flag(inode, FI_PIN_FILE);
>         f2fs_precache_extents(inode);
>         f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
> -       return 0;
> +       return ret;
>  }
>
>  static void f2fs_swap_deactivate(struct file *file)
> --
> 2.18.0.rc1
>
>
>
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