The patch titled
Subject: mm: migration: factor out code to compute expected number of page references
has been added to the -mm tree. Its filename is
mm-migration-factor-out-code-to-compute-expected-number-of-page-references.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-migration-factor-out-code-to-compute-expected-number-of-page-references.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-migration-factor-out-code-to-compute-expected-number-of-page-references.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: mm: migration: factor out code to compute expected number of page references
Patch series "mm: migrate: Fix page migration stalls for blkdev pages".
This patchset deals with page migration stalls that were reported by our
customer due to a block device page that had a bufferhead that was in the
bh LRU cache.
The patchset modifies the page migration code so that bufferheads are
completely handled inside buffer_migrate_page() and then provides a new
migration helper for pages with buffer heads that is safe to use even for
block device pages and that also deals with bh lrus.
This patch (of 6):
Factor out function to compute number of expected page references in
migrate_page_move_mapping(). Note that we move hpage_nr_pages() and
page_has_private() checks from under xas_lock_irq() however this is safe
since we hold page lock.
Link: http://lkml.kernel.org/r/20181211172143.7358-2-jack@xxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/migrate.c~mm-migration-factor-out-code-to-compute-expected-number-of-page-references
+++ a/mm/migrate.c
@@ -424,6 +424,22 @@ static inline bool buffer_migrate_lock_b
}
#endif /* CONFIG_BLOCK */
+static int expected_page_refs(struct page *page)
+{
+ int expected_count = 1;
+
+ /*
+ * Device public or private pages have an extra refcount as they are
+ * ZONE_DEVICE pages.
+ */
+ expected_count += is_device_private_page(page);
+ expected_count += is_device_public_page(page);
+ if (page->mapping)
+ expected_count += hpage_nr_pages(page) + page_has_private(page);
+
+ return expected_count;
+}
+
/*
* Replace the page in the mapping.
*
@@ -440,14 +456,7 @@ int migrate_page_move_mapping(struct add
XA_STATE(xas, &mapping->i_pages, page_index(page));
struct zone *oldzone, *newzone;
int dirty;
- int expected_count = 1 + extra_count;
-
- /*
- * Device public or private pages have an extra refcount as they are
- * ZONE_DEVICE pages.
- */
- expected_count += is_device_private_page(page);
- expected_count += is_device_public_page(page);
+ int expected_count = expected_page_refs(page) + extra_count;
if (!mapping) {
/* Anonymous page without mapping */
@@ -467,8 +476,6 @@ int migrate_page_move_mapping(struct add
newzone = page_zone(newpage);
xas_lock_irq(&xas);
-
- expected_count += hpage_nr_pages(page) + page_has_private(page);
if (page_count(page) != expected_count || xas_load(&xas) != page) {
xas_unlock_irq(&xas);
return -EAGAIN;
_
Patches currently in -mm which might be from jack@xxxxxxx are
mm-migration-factor-out-code-to-compute-expected-number-of-page-references.patch
mm-migrate-lock-buffers-before-migrate_page_move_mapping.patch
mm-migrate-move-migrate_page_lock_buffers.patch
mm-migrate-provide-buffer_migrate_page_norefs.patch
blkdev-avoid-migration-stalls-for-blkdev-pages.patch
mm-migrate-drop-unused-argument-of-migrate_page_move_mapping.patch
