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

[Chao Yu]

Hi Ju Hyung,

On 2020/2/7 14:42, Ju Hyung Park wrote:
> Hi Chao,
> 
> I think this should be sent to linux-stable.
> Thoughts?

Yup, I forgot to Cc stable mailing list, let me resend it.

Thanks for reminding me that.

Thanks,

> 
> 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
>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> .
>