The patch titled
Subject: mm: migrate: lock buffers before migrate_page_move_mapping()
has been added to the -mm tree. Its filename is
mm-migrate-lock-buffers-before-migrate_page_move_mapping.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-lock-buffers-before-migrate_page_move_mapping.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-lock-buffers-before-migrate_page_move_mapping.patch
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------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: mm: migrate: lock buffers before migrate_page_move_mapping()
Lock buffers before calling into migrate_page_move_mapping() so that that
function doesn't have to know about buffers (which is somewhat unexpected
anyway) and all the buffer head logic is in buffer_migrate_page().
Link: http://lkml.kernel.org/r/20181211172143.7358-3-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-migrate-lock-buffers-before-migrate_page_move_mapping
+++ a/mm/migrate.c
@@ -487,20 +487,6 @@ int migrate_page_move_mapping(struct add
}
/*
- * In the async migration case of moving a page with buffers, lock the
- * buffers using trylock before the mapping is moved. If the mapping
- * was moved, we later failed to lock the buffers and could not move
- * the mapping back due to an elevated page count, we would have to
- * block waiting on other references to be dropped.
- */
- if (mode == MIGRATE_ASYNC && head &&
- !buffer_migrate_lock_buffers(head, mode)) {
- page_ref_unfreeze(page, expected_count);
- xas_unlock_irq(&xas);
- return -EAGAIN;
- }
-
- /*
* Now we know that no one else is looking at the page:
* no turning back from here.
*/
@@ -775,24 +761,23 @@ int buffer_migrate_page(struct address_s
{
struct buffer_head *bh, *head;
int rc;
+ int expected_count;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page, mode);
- head = page_buffers(page);
+ /* Check whether page does not have extra refs before we do more work */
+ expected_count = expected_page_refs(page);
+ if (page_count(page) != expected_count)
+ return -EAGAIN;
- rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
+ head = page_buffers(page);
+ if (!buffer_migrate_lock_buffers(head, mode))
+ return -EAGAIN;
+ rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
if (rc != MIGRATEPAGE_SUCCESS)
- return rc;
-
- /*
- * In the async case, migrate_page_move_mapping locked the buffers
- * with an IRQ-safe spinlock held. In the sync case, the buffers
- * need to be locked now
- */
- if (mode != MIGRATE_ASYNC)
- BUG_ON(!buffer_migrate_lock_buffers(head, mode));
+ goto unlock_buffers;
ClearPagePrivate(page);
set_page_private(newpage, page_private(page));
@@ -814,6 +799,8 @@ int buffer_migrate_page(struct address_s
else
migrate_page_states(newpage, page);
+ rc = MIGRATEPAGE_SUCCESS;
+unlock_buffers:
bh = head;
do {
unlock_buffer(bh);
@@ -822,7 +809,7 @@ int buffer_migrate_page(struct address_s
} while (bh != head);
- return MIGRATEPAGE_SUCCESS;
+ return rc;
}
EXPORT_SYMBOL(buffer_migrate_page);
#endif
_
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
