On 2021/3/31 17:34, Yi Zhuang wrote:
In the cache writing process, if it is an atomic file, increase the page count of F2FS_WB_CP_DATA, otherwise increase the page count of F2FS_WB_DATA.When you step into the hook branch due to insufficient memory in f2fs_write_begin, f2fs_drop_inmem_pages_all will be called to traverse all atomic inodes and clear the FI_ATOMIC_FILE mark of all atomic files. In f2fs_drop_inmem_pages，first acquire the inmem_lock , revoke all the inmem_pages, and then clear the FI_ATOMIC_FILE mark. Before this mark is cleared, other threads may hold inmem_lock to add inmem_pages to the inode that has just been emptied inmem_pages, and increase the page count of F2FS_WB_CP_DATA. When the IO returns, it is found that the FI_ATOMIC_FILE flag is cleared by f2fs_drop_inmem_pages_all, and f2fs_is_atomic_file returns false,which causes the page count of F2FS_WB_DATA to be decremented. The page count of F2FS_WB_CP_DATA cannot be cleared. Finally, hungtask is triggered in f2fs_wait_on_all_pages because get_pages will never return zero. process A: process B: f2fs_drop_inmem_pages_all ->f2fs_drop_inmem_pages of inode#1 ->mutex_lock(&fi->inmem_lock) ->__revoke_inmem_pages of inode#1 f2fs_ioc_commit_atomic_write ->mutex_unlock(&fi->inmem_lock) ->f2fs_commit_inmem_pages of inode#1 ->mutex_lock(&fi->inmem_lock) ->__f2fs_commit_inmem_pages ->f2fs_do_write_data_page ->f2fs_outplace_write_data ->do_write_page ->f2fs_submit_page_write ->inc_page_count(sbi, F2FS_WB_CP_DATA ) ->mutex_unlock(&fi->inmem_lock) ->spin_lock(&sbi->inode_lock[ATOMIC_FILE]); ->clear_inode_flag(inode, FI_ATOMIC_FILE) ->spin_unlock(&sbi->inode_lock[ATOMIC_FILE]) f2fs_write_end_io ->dec_page_count(sbi, F2FS_WB_DATA ); We can fix the problem by putting the action of clearing the FI_ATOMIC_FILE mark into the inmem_lock lock. This operation can ensure that no one will submit the inmem pages before the FI_ATOMIC_FILE mark is cleared, so that there will be no atomic writes waiting for writeback. Fixes: 57864ae5ce3a ("f2fs: limit # of inmemory pages") Signed-off-by: Yi Zhuang <[email protected]>
Reviewed-by: Chao Yu <[email protected]> Thanks, _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
