• Jaegeuk Kim's avatar
    f2fs: avoid infinite GC loop due to stale atomic files · 743b620c
    Jaegeuk Kim authored
    If committing atomic pages is failed when doing f2fs_do_sync_file(), we can
    get commited pages but atomic_file being still set like:
    
    - inmem:    0, atomic IO:    4 (Max.   10), volatile IO:    0 (Max.    0)
    
    If GC selects this block, we can get an infinite loop like this:
    
    f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
    f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
    f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
    f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
    f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA
    f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096
    f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234
    f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c
    
    In that moment, we can observe:
    
    [Before]
    Try to move 5084219 blocks (BG: 384508)
      - data blocks : 4962373 (274483)
      - node blocks : 121846 (110025)
    Skipped : atomic write 4534686 (10)
    
    [After]
    Try to move 5088973 blocks (BG: 384508)
      - data blocks : 4967127 (274483)
      - node blocks : 121846 (110025)
    Skipped : atomic write 4539440 (10)
    
    So, refactor atomic_write flow like this:
    1. start_atomic_write
     - add inmem_list and set atomic_file
    
    2. write()
     - register it in inmem_pages
    
    3. commit_atomic_write
     - if no error, f2fs_drop_inmem_pages()
     - f2fs_commit_inmme_pages() failed
       : __revoked_inmem_pages() was done
     - f2fs_do_sync_file failed
       : abort_atomic_write later
    
    4. abort_atomic_write
     - f2fs_drop_inmem_pages
    
    5. f2fs_drop_inmem_pages
     - clear atomic_file
     - remove inmem_list
    
    Based on this change, when GC fails to move block in atomic_file,
    f2fs_drop_inmem_pages_all() can call f2fs_drop_inmem_pages().
    Reviewed-by: default avatarChao Yu <yuchao0@huawei.com>
    Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
    743b620c
file.c 78.6 KB