On 08.06.22 17:02, Matthew Wilcox (Oracle) wrote: > Provide a folio-based replacement for aops->migratepage. Update the > documentation to document migrate_folio instead of migratepage. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > --- > Documentation/filesystems/locking.rst | 5 ++-- > Documentation/filesystems/vfs.rst | 13 ++++++----- > Documentation/vm/page_migration.rst | 33 ++++++++++++++------------- > include/linux/fs.h | 4 +++- > mm/compaction.c | 4 +++- > mm/migrate.c | 11 +++++---- > 6 files changed, 40 insertions(+), 30 deletions(-) > > diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst > index c0fe711f14d3..3d28b23676bd 100644 > --- a/Documentation/filesystems/locking.rst > +++ b/Documentation/filesystems/locking.rst > @@ -253,7 +253,8 @@ prototypes:: > void (*free_folio)(struct folio *); > int (*direct_IO)(struct kiocb *, struct iov_iter *iter); > bool (*isolate_page) (struct page *, isolate_mode_t); > - int (*migratepage)(struct address_space *, struct page *, struct page *); > + int (*migrate_folio)(struct address_space *, struct folio *dst, > + struct folio *src, enum migrate_mode); > void (*putback_page) (struct page *); isolate_page/putback_page are leftovers from the previous patch, no? > int (*launder_folio)(struct folio *); > bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count); > @@ -281,7 +282,7 @@ release_folio: yes > free_folio: yes > direct_IO: > isolate_page: yes > -migratepage: yes (both) > +migrate_folio: yes (both) > putback_page: yes Dito. > launder_folio: yes > is_partially_uptodate: yes > diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst > index a08c652467d7..3ae1b039b03f 100644 > --- a/Documentation/filesystems/vfs.rst > +++ b/Documentation/filesystems/vfs.rst > @@ -740,7 +740,8 @@ cache in your filesystem. The following members are defined: > /* isolate a page for migration */ > bool (*isolate_page) (struct page *, isolate_mode_t); > /* migrate the contents of a page to the specified target */ > - int (*migratepage) (struct page *, struct page *); > + int (*migrate_folio)(struct mapping *, struct folio *dst, > + struct folio *src, enum migrate_mode); > /* put migration-failed page back to right list */ > void (*putback_page) (struct page *); Dito. > int (*launder_folio) (struct folio *); > @@ -935,12 +936,12 @@ cache in your filesystem. The following members are defined: > is successfully isolated, VM marks the page as PG_isolated via > __SetPageIsolated. > > -``migrate_page`` > +``migrate_folio`` > This is used to compact the physical memory usage. If the VM > - wants to relocate a page (maybe off a memory card that is > - signalling imminent failure) it will pass a new page and an old > - page to this function. migrate_page should transfer any private > - data across and update any references that it has to the page. > + wants to relocate a folio (maybe from a memory device that is > + signalling imminent failure) it will pass a new folio and an old > + folio to this function. migrate_folio should transfer any private > + data across and update any references that it has to the folio. > > ``putback_page`` > Called by the VM when isolated page's migration fails. Dito. > diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst > index 8c5cb8147e55..e0f73ddfabb1 100644 > --- a/Documentation/vm/page_migration.rst > +++ b/Documentation/vm/page_migration.rst > @@ -181,22 +181,23 @@ which are function pointers of struct address_space_operations. > Once page is successfully isolated, VM uses page.lru fields so driver > shouldn't expect to preserve values in those fields. > > -2. ``int (*migratepage) (struct address_space *mapping,`` > -| ``struct page *newpage, struct page *oldpage, enum migrate_mode);`` > - > - After isolation, VM calls migratepage() of driver with the isolated page. > - The function of migratepage() is to move the contents of the old page to the > - new page > - and set up fields of struct page newpage. Keep in mind that you should > - indicate to the VM the oldpage is no longer movable via __ClearPageMovable() > - under page_lock if you migrated the oldpage successfully and returned > - MIGRATEPAGE_SUCCESS. If driver cannot migrate the page at the moment, driver > - can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time > - because VM interprets -EAGAIN as "temporary migration failure". On returning > - any error except -EAGAIN, VM will give up the page migration without > - retrying. > - > - Driver shouldn't touch the page.lru field while in the migratepage() function. > +2. ``int (*migrate_folio) (struct address_space *mapping,`` > +| ``struct folio *dst, struct folio *src, enum migrate_mode);`` > + > + After isolation, VM calls the driver's migrate_folio() with the > + isolated folio. The purpose of migrate_folio() is to move the contents > + of the source folio to the destination folio and set up the fields > + of destination folio. Keep in mind that you should indicate to the > + VM the source folio is no longer movable via __ClearPageMovable() > + under folio if you migrated the source successfully and returned > + MIGRATEPAGE_SUCCESS. If driver cannot migrate the folio at the > + moment, driver can return -EAGAIN. On -EAGAIN, VM will retry folio > + migration in a short time because VM interprets -EAGAIN as "temporary > + migration failure". On returning any error except -EAGAIN, VM will > + give up the folio migration without retrying. > + > + Driver shouldn't touch the folio.lru field while in the migrate_folio() > + function. > > 3. ``void (*putback_page)(struct page *);`` Hmm, here it's a bit more complicated now, because we essentially have two paths: LRU+migrate_folio or !LRU+movable_ops (isolate/migrate/putback page) -- Thanks, David / dhildenb
