On Sun, Jun 04, 2023 at 01:33:06PM -0700, Darrick J. Wong wrote: > On Sun, Jun 04, 2023 at 09:10:55PM +0100, Matthew Wilcox wrote: > > On Sun, Jun 04, 2023 at 10:55:48AM -0700, Darrick J. Wong wrote: > > > On Fri, Jun 02, 2023 at 11:24:39PM +0100, Matthew Wilcox (Oracle) wrote: > > > > -->release_folio() is called when the kernel is about to try to drop the > > > > -buffers from the folio in preparation for freeing it. It returns false to > > > > -indicate that the buffers are (or may be) freeable. If ->release_folio is > > > > -NULL, the kernel assumes that the fs has no private interest in the buffers. > > > > +->release_folio() is called when the MM wants to make a change to the > > > > +folio that would invalidate the filesystem's private data. For example, > > > > +it may be about to be removed from the address_space or split. The folio > > > > +is locked and not under writeback. It may be dirty. The gfp parameter is > > > > +not usually used for allocation, but rather to indicate what the filesystem > > > > +may do to attempt to free the private data. The filesystem may > > > > +return false to indicate that the folio's private data cannot be freed. > > > > +If it returns true, it should have already removed the private data from > > > > +the folio. If a filesystem does not provide a ->release_folio method, > > > > +the kernel will call try_to_free_buffers(). > > > > > > the MM? Since you changed that above... :) > > > > > > With that nit fixed, > > > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > Well, is it the MM? At this point, the decision is made by > > filemap_release_folio(), which is the VFS, in my opinion ;-) > > It's in mm/filemap.c, which I think makes it squarely the pagecache/mm, > not the vfs. Changed this to: If a filesystem does not provide a ->release_folio method, the pagecache will assume that private data is buffer_heads and call try_to_free_buffers().
