• Chao Yu's avatar
    f2fs: fix wrong discard space · ca7f76e6
    Chao Yu authored
    Under heavy fsstress, we may triggle panic while issuing discard,
    because __check_sit_bitmap() detects that discard command may earse
    valid data blocks, the root cause is as below race stack described,
    since we removed lock when flushing quota data, quota data writeback
    may race with write_checkpoint(), so that it causes inconsistency in
    between cached discard entry and segment bitmap.
    
    - f2fs_write_checkpoint
     - block_operations
      - set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH)
     - f2fs_flush_sit_entries
      - add_discard_addrs
       - __set_bit_le(i, (void *)de->discard_map);
    						- f2fs_write_data_pages
    						 - f2fs_write_single_data_page
    						   : inode is quota one, cp_rwsem won't be locked
    						  - f2fs_do_write_data_page
    						   - f2fs_allocate_data_block
    						    - f2fs_wait_discard_bio
    						      : discard entry has not been added yet.
    						    - update_sit_entry
     - f2fs_clear_prefree_segments
      - f2fs_issue_discard
      : add discard entry
    
    In order to fix this, this patch uses node_write to serialize
    f2fs_allocate_data_block and checkpoint.
    
    Fixes: 435cbab9 ("f2fs: fix quota_sync failure due to f2fs_lock_op")
    Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
    Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
    ca7f76e6
segment.c 124 KB