On 2021/12/10 12:30, Hyeong-Jun Kim wrote:
There is a potential deadlock between writeback process and a process performing write_begin() or write_cache_pages() while trying to write same compress file, but not compressable, as below:[Process A] - doing checkpoint [Process B] [Process C] f2fs_write_cache_pages() - lock_page() [all pages in cluster, 0-31] - f2fs_write_multi_pages() - f2fs_write_raw_pages() - f2fs_write_single_data_page() - f2fs_do_write_data_page() - return -EAGAIN [f2fs_trylock_op() failed] - unlock_page(page) [e.g., page 0] - generic_perform_write() - f2fs_write_begin() - f2fs_prepare_compress_overwrite() - prepare_compress_overwrite() - lock_page() [e.g., page 0] - lock_page() [e.g., page 1] - lock_page(page) [e.g., page 0] Since there is no compress process, it is no longer necessary to hold locks on every pages in cluster within f2fs_write_raw_pages(). This patch changes f2fs_write_raw_pages() to release all locks first and then perform write same as the non-compress file in f2fs_write_cache_pages(). Fixes: 4c8ff7095bef ("f2fs: support data compression") Signed-off-by: Hyeong-Jun Kim <[email protected]> Signed-off-by: Sungjong Seo <[email protected]> Signed-off-by: Youngjin Gil <[email protected]>
Looks good to me, thanks for Fengnan and Hyeong-Jun's report and Hyeong-Jun's fixing. :) Reviewed-by: Chao Yu <[email protected]> Thanks, _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
