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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>
This commit is contained in:
Huang Ying 2014-09-07 11:05:20 +08:00 committed by Jaegeuk Kim
parent 721bd4d5c3
commit 9a01b56b1a
1 changed files with 6 additions and 0 deletions
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6
fs/f2fs/gc.c
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@ -423,6 +423,12 @@ next_step:
if (IS_ERR(node_page))
continue;
/* block may become invalid during get_node_page */
if (check_valid_map(sbi, segno, off) == 0) {
f2fs_put_page(node_page, 1);
continue;
}
/* set page dirty and write it */
if (gc_type == FG_GC) {
f2fs_wait_on_page_writeback(node_page, NODE);