The patch titled
Subject: mm: __isolate_lru_page_prepare() in isolate_migratepages_block()
has been added to the -mm tree. Its filename is
mm-__isolate_lru_page_prepare-in-isolate_migratepages_block.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-__isolate_lru_page_prepare-in-isolate_migratepages_block.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-__isolate_lru_page_prepare-in-isolate_migratepages_block.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: __isolate_lru_page_prepare() in isolate_migratepages_block()
__isolate_lru_page_prepare() conflates two unrelated functions, with the
flags to one disjoint from the flags to the other; and hides some of the
important checks outside of isolate_migratepages_block(), where the
sequence is better to be visible. It comes from the days of lumpy
reclaim, before compaction, when the combination made more sense.
Move what's needed by mm/compaction.c isolate_migratepages_block() inline
there, and what's needed by mm/vmscan.c isolate_lru_pages() inline there.
Shorten "isolate_mode" to "mode", so the sequence of conditions is easier
to read. Declare a "mapping" variable, to save one call to page_mapping()
(but not another: calling again after page is locked is necessary).
Simplify isolate_lru_pages() with a "move_to" list pointer.
Link: https://lkml.kernel.org/r/879d62a8-91cc-d3c6-fb3b-69768236df68@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Alex Shi <alexs@xxxxxxxxxx>
Cc: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 1
mm/compaction.c | 51 +++++++++++++++++---
mm/vmscan.c | 101 +++++++----------------------------------
3 files changed, 62 insertions(+), 91 deletions(-)
--- a/include/linux/swap.h~mm-__isolate_lru_page_prepare-in-isolate_migratepages_block
+++ a/include/linux/swap.h
@@ -384,7 +384,6 @@ extern void lru_cache_add_inactive_or_un
extern unsigned long zone_reclaimable_pages(struct zone *zone);
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *mask);
-extern bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_pages,
gfp_t gfp_mask,
--- a/mm/compaction.c~mm-__isolate_lru_page_prepare-in-isolate_migratepages_block
+++ a/mm/compaction.c
@@ -785,7 +785,7 @@ static bool too_many_isolated(pg_data_t
* @cc: Compaction control structure.
* @low_pfn: The first PFN to isolate
* @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
- * @isolate_mode: Isolation mode to be used.
+ * @mode: Isolation mode to be used.
*
* Isolate all pages that can be migrated from the range specified by
* [low_pfn, end_pfn). The range is expected to be within same pageblock.
@@ -798,7 +798,7 @@ static bool too_many_isolated(pg_data_t
*/
static int
isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
- unsigned long end_pfn, isolate_mode_t isolate_mode)
+ unsigned long end_pfn, isolate_mode_t mode)
{
pg_data_t *pgdat = cc->zone->zone_pgdat;
unsigned long nr_scanned = 0, nr_isolated = 0;
@@ -806,6 +806,7 @@ isolate_migratepages_block(struct compac
unsigned long flags = 0;
struct lruvec *locked = NULL;
struct page *page = NULL, *valid_page = NULL;
+ struct address_space *mapping;
unsigned long start_pfn = low_pfn;
bool skip_on_failure = false;
unsigned long next_skip_pfn = 0;
@@ -990,7 +991,7 @@ isolate_migratepages_block(struct compac
locked = NULL;
}
- if (!isolate_movable_page(page, isolate_mode))
+ if (!isolate_movable_page(page, mode))
goto isolate_success;
}
@@ -1002,15 +1003,15 @@ isolate_migratepages_block(struct compac
* so avoid taking lru_lock and isolating it unnecessarily in an
* admittedly racy check.
*/
- if (!page_mapping(page) &&
- page_count(page) > page_mapcount(page))
+ mapping = page_mapping(page);
+ if (!mapping && page_count(page) > page_mapcount(page))
goto isolate_fail;
/*
* Only allow to migrate anonymous pages in GFP_NOFS context
* because those do not depend on fs locks.
*/
- if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
+ if (!(cc->gfp_mask & __GFP_FS) && mapping)
goto isolate_fail;
/*
@@ -1021,9 +1022,45 @@ isolate_migratepages_block(struct compac
if (unlikely(!get_page_unless_zero(page)))
goto isolate_fail;
- if (!__isolate_lru_page_prepare(page, isolate_mode))
+ /* Only take pages on LRU: a check now makes later tests safe */
+ if (!PageLRU(page))
goto isolate_fail_put;
+ /* Compaction might skip unevictable pages but CMA takes them */
+ if (!(mode & ISOLATE_UNEVICTABLE) && PageUnevictable(page))
+ goto isolate_fail_put;
+
+ /*
+ * To minimise LRU disruption, the caller can indicate with
+ * ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages
+ * it will be able to migrate without blocking - clean pages
+ * for the most part. PageWriteback would require blocking.
+ */
+ if ((mode & ISOLATE_ASYNC_MIGRATE) && PageWriteback(page))
+ goto isolate_fail_put;
+
+ if ((mode & ISOLATE_ASYNC_MIGRATE) && PageDirty(page)) {
+ bool migrate_dirty;
+
+ /*
+ * Only pages without mappings or that have a
+ * ->migratepage callback are possible to migrate
+ * without blocking. However, we can be racing with
+ * truncation so it's necessary to lock the page
+ * to stabilise the mapping as truncation holds
+ * the page lock until after the page is removed
+ * from the page cache.
+ */
+ if (!trylock_page(page))
+ goto isolate_fail_put;
+
+ mapping = page_mapping(page);
+ migrate_dirty = !mapping || mapping->a_ops->migratepage;
+ unlock_page(page);
+ if (!migrate_dirty)
+ goto isolate_fail_put;
+ }
+
/* Try isolate the page */
if (!TestClearPageLRU(page))
goto isolate_fail_put;
--- a/mm/vmscan.c~mm-__isolate_lru_page_prepare-in-isolate_migratepages_block
+++ a/mm/vmscan.c
@@ -1999,69 +1999,6 @@ unsigned int reclaim_clean_pages_from_li
}
/*
- * Attempt to remove the specified page from its LRU. Only take this page
- * if it is of the appropriate PageActive status. Pages which are being
- * freed elsewhere are also ignored.
- *
- * page: page to consider
- * mode: one of the LRU isolation modes defined above
- *
- * returns true on success, false on failure.
- */
-bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
-{
- /* Only take pages on the LRU. */
- if (!PageLRU(page))
- return false;
-
- /* Compaction should not handle unevictable pages but CMA can do so */
- if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
- return false;
-
- /*
- * To minimise LRU disruption, the caller can indicate that it only
- * wants to isolate pages it will be able to operate on without
- * blocking - clean pages for the most part.
- *
- * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
- * that it is possible to migrate without blocking
- */
- if (mode & ISOLATE_ASYNC_MIGRATE) {
- /* All the caller can do on PageWriteback is block */
- if (PageWriteback(page))
- return false;
-
- if (PageDirty(page)) {
- struct address_space *mapping;
- bool migrate_dirty;
-
- /*
- * Only pages without mappings or that have a
- * ->migratepage callback are possible to migrate
- * without blocking. However, we can be racing with
- * truncation so it's necessary to lock the page
- * to stabilise the mapping as truncation holds
- * the page lock until after the page is removed
- * from the page cache.
- */
- if (!trylock_page(page))
- return false;
-
- mapping = page_mapping(page);
- migrate_dirty = !mapping || mapping->a_ops->migratepage;
- unlock_page(page);
- if (!migrate_dirty)
- return false;
- }
- }
-
- if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
- return false;
-
- return true;
-}
-
-/*
* Update LRU sizes after isolating pages. The LRU size updates must
* be complete before mem_cgroup_update_lru_size due to a sanity check.
*/
@@ -2112,11 +2049,11 @@ static unsigned long isolate_lru_pages(u
unsigned long skipped = 0;
unsigned long scan, total_scan, nr_pages;
LIST_HEAD(pages_skipped);
- isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED);
total_scan = 0;
scan = 0;
while (scan < nr_to_scan && !list_empty(src)) {
+ struct list_head *move_to = src;
struct page *page;
page = lru_to_page(src);
@@ -2126,9 +2063,9 @@ static unsigned long isolate_lru_pages(u
total_scan += nr_pages;
if (page_zonenum(page) > sc->reclaim_idx) {
- list_move(&page->lru, &pages_skipped);
nr_skipped[page_zonenum(page)] += nr_pages;
- continue;
+ move_to = &pages_skipped;
+ goto move;
}
/*
@@ -2136,37 +2073,34 @@ static unsigned long isolate_lru_pages(u
* return with no isolated pages if the LRU mostly contains
* ineligible pages. This causes the VM to not reclaim any
* pages, triggering a premature OOM.
- *
- * Account all tail pages of THP. This would not cause
- * premature OOM since __isolate_lru_page() returns -EBUSY
- * only when the page is being freed somewhere else.
+ * Account all tail pages of THP.
*/
scan += nr_pages;
- if (!__isolate_lru_page_prepare(page, mode)) {
- /* It is being freed elsewhere */
- list_move(&page->lru, src);
- continue;
- }
+
+ if (!PageLRU(page))
+ goto move;
+ if (!sc->may_unmap && page_mapped(page))
+ goto move;
+
/*
* Be careful not to clear PageLRU until after we're
* sure the page is not being freed elsewhere -- the
* page release code relies on it.
*/
- if (unlikely(!get_page_unless_zero(page))) {
- list_move(&page->lru, src);
- continue;
- }
+ if (unlikely(!get_page_unless_zero(page)))
+ goto move;
if (!TestClearPageLRU(page)) {
/* Another thread is already isolating this page */
put_page(page);
- list_move(&page->lru, src);
- continue;
+ goto move;
}
nr_taken += nr_pages;
nr_zone_taken[page_zonenum(page)] += nr_pages;
- list_move(&page->lru, dst);
+ move_to = dst;
+move:
+ list_move(&page->lru, move_to);
}
/*
@@ -2190,7 +2124,8 @@ static unsigned long isolate_lru_pages(u
}
*nr_scanned = total_scan;
trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
- total_scan, skipped, nr_taken, mode, lru);
+ total_scan, skipped, nr_taken,
+ sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru);
update_lru_sizes(lruvec, lru, nr_zone_taken);
return nr_taken;
}
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-fs-delete-pf_swapwrite.patch
mm-__isolate_lru_page_prepare-in-isolate_migratepages_block.patch
tmpfs-support-for-file-creation-time-fix.patch
shmem-mapping_set_exiting-to-help-mapped-resilience.patch
mm-_install_special_mapping-apply-vm_locked_clear_mask.patch
mempolicy-mbind_range-set_policy-after-vma_merge.patch
mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch
mm-thp-clearpagedoublemap-in-first-page_add_file_rmap.patch
mm-delete-__clearpagewaiters.patch
mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch
mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch
mm-warn-on-deleting-redirtied-only-if-accounted.patch
mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared.patch
