f2fs: avoid node page to be written twice in gc_node_segment
authorHuang Ying <ying.huang@intel.com>
Sun, 7 Sep 2014 03:05:20 +0000 (11:05 +0800)
committerIan Chang <ianc@nvidia.com>
Wed, 27 Jan 2016 10:04:13 +0000 (18:04 +0800)
commitd0f62f1371735aeaafd0bb5d7a61417fb7838d51
treecb8ea3809f9a8abfc893c2353cfe1a98eed1b1e1
parentffbe597129e9afedc09438bb59e09fd9a0851098
f2fs: avoid node page to be written twice in gc_node_segment

In gc_node_segment, if node page gc is run concurrently with node page
writeback, and check_valid_map and get_node_page run after page locked
and before cur_valid_map is updated as below, it is possible for the
page to be written twice unnecessarily.

sync_node_pages
  try_lock_page
  ...
check_valid_map   f2fs_write_node_page
    ...
    write_node_page
      do_write_page
        allocate_data_block
  ...
  refresh_sit_entry /* update cur_valid_map */
  ...
    ...
    unlock_page
get_node_page
...
set_page_dirty
...
f2fs_put_page
  unlock_page

This can be solved via calling check_valid_map after get_node_page again.

Signed-off-by: Huang, Ying <ying.huang@intel.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
fs/f2fs/gc.c