According to stable write assumptions (1d1d1a767206fb) grab_cache_page_write_begin() now calls relaxed method wait_for_stable_page() which will wait for writeback to finish only if bdi demand that. Commit message states that ext4 may not wait But there are a lot of write-paths where we expect that: BUG_ON(!PageLocked(page)); BUG_ON(PageWriteback(page)); And the only reason we avoid this bugon is because of commit 47564bfb95b which use following trick to avoid lock inversion over journal_start: page = grab_cache_page_write_begin() unlock_page(page); ext4_journal_start() lock_page(page); wait_on_page_writeback(page); <<<< unconditional wait So as far as I understand this was done just by occasion because ext4_page_mkwrite() use wait_for_stable_page(). So here is my question: Do we have to wait for page's writeback to finish for all write paths in ext4 code or we may use wait_for_stable_page() and should cleanup all places where we may trigger BUG_ON(PageWriteback(page)); -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
