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f2fs: fix an infinite loop when flush nodes in cp 

Thread A			Thread B

- write_checkpoint
 - block_operations
   -blk_start_plug
    -sync_node_pages		- f2fs_do_sync_file
				 - fsync_node_pages
				  - f2fs_wait_on_page_writeback

Thread A wait for global F2FS_DIRTY_NODES decreased to zero,
it start a plug list, some requests have been added to this list.
Thread B lock one dirty node page, and wait this page write back.
But this page has been in plug list of thread A with PG_writeback flag.
Thread A keep on running and its plug list has no chance to finish,
so it seems a deadlock between cp and fsync path.

This patch add a wait on page write back before set node page dirty
to avoid this problem.

Signed-off-by: Yunlei He <heyunlei@huawei.com>
Signed-off-by: Pengyang Hou <houpengyang@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Yunlei He 2016-11-16 17:26:24 +08:00 committed by Jaegeuk Kim
parent 36951b38d1
commit d40a43af0a
1 changed files with 1 additions and 0 deletions
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fs/f2fs/node.c
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@ -1410,6 +1410,7 @@ continue_unlock:
"Retry to write fsync mark: ino=%u, idx=%lx",
ino, last_page->index);
lock_page(last_page);
f2fs_wait_on_page_writeback(last_page, NODE, true);
set_page_dirty(last_page);
unlock_page(last_page);
goto retry;