On Fri, Nov 18, 2022 at 10:37:35AM +0000, David Howells wrote: > A hint flag is added to the writeback_control struct so that a filesystem > can say that the write is triggered by write_begin seeing a conflicting > write. This causes do_writepages() to do a single pass of the loop only. Not a huge fan of that, especially as write_begin is not really a method, but just an awkward hook in legacy write implementations. I'd much rather have a private pointer in the writeback_control and make the behavior implementation specific. It will need to be split into a separate patch with proper documentation and a CC to linux-mm. > (1) afs_write_back_from_locked_folio() could be called directly rather > than calling filemap_fdatawrite_wbc(), but that would avoid the > control group stuff that wbc_attach_and_unlock_inode() and co. seem to > do. Do I actually need to do this? That would be much preferred over the for_write_begin hack, given that write_begin really isn't a well defined method but a hacky hook for legacy write implementations. > (2) afs_writepages_region() has a loop in it to generate multiple writes. > do_writepages() also acquired a loop[2] which will also generate > multiple writes. Should I remove the loop from > afs_writepages_region() and leave it to the caller of ->writepages()? Dropping out of ->writpages inside a page does seem a bit problematic, so you probably want to keep the loop.
