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.hu...@intel.com>
---
fs/f2fs/gc.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -421,6 +421,12 @@ 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);
--
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