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f2fs: fix race between write_checkpoint and write_begin

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The following race could lead to inconsistent SIT bitmap:

Task A                          Task B
======                          ======
f2fs_write_checkpoint
  block_operations
    f2fs_lock_all
      down_write(node_change)
      down_write(node_write)
      ... sync ...
      up_write(node_change)
                                f2fs_file_write_iter
                                  set_inode_flag(FI_NO_PREALLOC)
                                  ......
                                  f2fs_write_begin(index=0, has inline data)
                                    prepare_write_begin
                                      __do_map_lock(AIO) => down_read(node_change)
                                      f2fs_convert_inline_page => update SIT
                                      __do_map_lock(AIO) => up_read(node_change)
  f2fs_flush_sit_entries <= inconsistent SIT
  finish write checkpoint
  sudden-power-off

If SPO occurs after checkpoint is finished, SIT bitmap will be set
incorrectly.

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Sheng Yong 2018-11-14 19:34:28 +08:00 committed by Jaegeuk Kim
parent 4e240d1bab
commit 2866fb16d6
1 changed files with 10 additions and 2 deletions
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12
fs/f2fs/data.c
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@ -2322,6 +2322,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
bool locked = false;
struct extent_info ei = {0,0,0};
int err = 0;
int flag;
/*
* we already allocated all the blocks, so we don't need to get
@ -2331,9 +2332,15 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
!is_inode_flag_set(inode, FI_NO_PREALLOC))
return 0;
/* f2fs_lock_op avoids race between write CP and convert_inline_page */
if (f2fs_has_inline_data(inode) && pos + len > MAX_INLINE_DATA(inode))
flag = F2FS_GET_BLOCK_DEFAULT;
else
flag = F2FS_GET_BLOCK_PRE_AIO;
if (f2fs_has_inline_data(inode) ||
(pos & PAGE_MASK) >= i_size_read(inode)) {
__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, true);
__do_map_lock(sbi, flag, true);
locked = true;
}
restart:
@ -2371,6 +2378,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
f2fs_put_dnode(&dn);
__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO,
true);
WARN_ON(flag != F2FS_GET_BLOCK_PRE_AIO);
locked = true;
goto restart;
}
@ -2384,7 +2392,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
f2fs_put_dnode(&dn);
unlock_out:
if (locked)
__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, false);
__do_map_lock(sbi, flag, false);
return err;
}