On Fri, Aug 09, 2019 at 03:58:20PM -0700, ira.weiny@xxxxxxxxx wrote: > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > Callers of dax_layout_busy_page() are only rarely operating on the > entire file of concern. > > Teach dax_layout_busy_page() to operate on a sub-range of the > address_space provided. Specifying 0 - ULONG_MAX however, will continue > to operate on the "entire file" and XFS is split out to a separate patch > by this method. > > This could potentially speed up dax_layout_busy_page() as well. I need this functionality as well for virtio_fs and posted a patch for this. https://lkml.org/lkml/2019/8/21/825 Given this is an optimization which existing users can benefit from already, this patch could probably be pushed upstream independently. > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > --- > Changes from RFC v1 > Fix 0-day build errors > > fs/dax.c | 15 +++++++++++---- > fs/ext4/ext4.h | 2 +- > fs/ext4/extents.c | 6 +++--- > fs/ext4/inode.c | 19 ++++++++++++------- > fs/xfs/xfs_file.c | 3 ++- > include/linux/dax.h | 6 ++++-- > 6 files changed, 33 insertions(+), 18 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index a14ec32255d8..3ad19c384454 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -573,8 +573,11 @@ bool dax_mapping_is_dax(struct address_space *mapping) > EXPORT_SYMBOL_GPL(dax_mapping_is_dax); > > /** > - * dax_layout_busy_page - find first pinned page in @mapping > + * dax_layout_busy_page - find first pinned page in @mapping within > + * the range @off - @off + @len > * @mapping: address space to scan for a page with ref count > 1 > + * @off: offset to start at > + * @len: length to scan through > * > * DAX requires ZONE_DEVICE mapped pages. These pages are never > * 'onlined' to the page allocator so they are considered idle when > @@ -587,9 +590,13 @@ EXPORT_SYMBOL_GPL(dax_mapping_is_dax); > * to be able to run unmap_mapping_range() and subsequently not race > * mapping_mapped() becoming true. > */ > -struct page *dax_layout_busy_page(struct address_space *mapping) > +struct page *dax_layout_busy_page(struct address_space *mapping, > + loff_t off, loff_t len) > { > - XA_STATE(xas, &mapping->i_pages, 0); > + unsigned long start_idx = off >> PAGE_SHIFT; > + unsigned long end_idx = (len == ULONG_MAX) ? ULONG_MAX > + : start_idx + (len >> PAGE_SHIFT); > + XA_STATE(xas, &mapping->i_pages, start_idx); > void *entry; > unsigned int scanned = 0; > struct page *page = NULL; > @@ -612,7 +619,7 @@ struct page *dax_layout_busy_page(struct address_space *mapping) > unmap_mapping_range(mapping, 0, 0, 1); Should we unmap only those pages which fall in the range specified by caller. Unmapping whole file seems to be less efficient. Thanks Vivek
