On Thu, Nov 17, 2022 at 12:09:00AM +0530, Ritesh Harjani (IBM) wrote: > reclaim. Now IIUC from previous discussions [1][2][3], reclaims happens from > the tail end of the LRU list which could do an I/O of a single page while > an ongoing writeback was in progress of multiple pages. This disrupts the I/O > pattern to become more random in nature, compared to, if we would have let > writeback/flusher do it's job of writing back dirty pages. Yes. > Also many filesystems behave very differently within their ->writepage calls, > e.g. ext4 doesn't actually write in ->writepage for DELAYED blocks. I don't think it's many file systems. As far as I can tell only ext4 actually is significantly different. > 2. Now the other place from where ->writepage can be called from is, writeout() > function, which is a fallback function for migration (fallback_migrate_folio()). > fallback_migrate_folio() is called from move_to_new_folio() if ->migrate_folio > is not defined for the FS. Also there is generic_writepages and folio_write_one/write_one_page. > Is above a correct understanding? Yes.
