Re: [RFC PATCH v2 06/19] fs/ext4: Teach dax_layout_busy_page() to operate on a sub-range
From: Vivek Goyal <vgoyal@redhat.com>
Date: 2019-08-23 15:18:32
Also in:
linux-fsdevel, linux-mm, linux-rdma, linux-xfs, lkml, nvdimm
On Fri, Aug 09, 2019 at 03:58:20PM -0700, ira.weiny@intel.com wrote:
From: Ira Weiny <ira.weiny@intel.com> 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.
quoted hunk ↗ jump to hunk
Signed-off-by: Ira Weiny <ira.weiny@intel.com> --- 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