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Commit 2866fb16 authored by Sheng Yong's avatar Sheng Yong Committed by Jaegeuk Kim
Browse files

f2fs: fix race between write_checkpoint and write_begin 



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: default avatarSheng Yong <shengyong1@huawei.com>
Reviewed-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent 4e240d1b

fs/f2fs/data.c

+10 −2
Original line number Original line Diff line number Diff line
@@ -2322,6 +2322,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi, 
	bool locked = false;

	bool locked = false;

	struct extent_info ei = {0,0,0};

	struct extent_info ei = {0,0,0};

	int err = 0;

	int err = 0;

	int flag;





	/*

	/*

	 * we already allocated all the blocks, so we don't need to get

	 * 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))

			!is_inode_flag_set(inode, FI_NO_PREALLOC))

		return 0;

		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) ||

	if (f2fs_has_inline_data(inode) ||

			(pos & PAGE_MASK) >= i_size_read(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;

		locked = true;

	}

	}

restart:

restart:
@@ -2371,6 +2378,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi, 
				f2fs_put_dnode(&dn);

				f2fs_put_dnode(&dn);

				__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO,

				__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO,

								true);

								true);

				WARN_ON(flag != F2FS_GET_BLOCK_PRE_AIO);

				locked = true;

				locked = true;

				goto restart;

				goto restart;

			}

			}
@@ -2384,7 +2392,7 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi, 
	f2fs_put_dnode(&dn);

	f2fs_put_dnode(&dn);

unlock_out:

unlock_out:

	if (locked)

	if (locked)

		__do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, false);

		__do_map_lock(sbi, flag, false);

	return err;

	return err;

}

}