---- 在 星期四, 2021-10-07 22:41:56 Jan Kara <jack@xxxxxxx> 撰写 ---- > On Thu 07-10-21 20:26:36, Chengguang Xu wrote: > > ---- 在 星期四, 2021-10-07 17:01:57 Jan Kara <jack@xxxxxxx> 撰写 ---- > > > > > > > + if (mapping_writably_mapped(upper->i_mapping) || > > > > + mapping_tagged(upper->i_mapping, PAGECACHE_TAG_WRITEBACK)) > > > > + iflag |= I_DIRTY_PAGES; > > > > + > > > > + iflag |= upper->i_state & I_DIRTY_ALL; > > > > > > Also since you call ->write_inode directly upper->i_state won't be updated > > > to reflect that inode has been written out (I_DIRTY flags get cleared in > > > __writeback_single_inode()). So it seems to me overlayfs will keep writing > > > out upper inode until flush worker on upper filesystem also writes the > > > inode and clears the dirty flags? So you rather need to call something like > > > write_inode_now() that will handle the flag clearing and do writeback list > > > handling for you? > > > > > > > Calling ->write_inode directly upper->i_state won't be updated, however, > > I don't think overlayfs will keep writing out upper inode since > > ->write_inode will be called when only overlay inode itself marked dirty. > > Am I missing something? > > Well, if upper->i_state is not updated, you are more or less guaranteed > upper->i_state & I_DIRTY_ALL != 0 and thus even overlay inode stays dirty. > And thus next time writeback runs you will see dirty overlay inode and > writeback the upper inode again although it is not necessary. > Hi Jan, Yes, I get the point now. Thanks for the explanation. Thanks, Chengguang
