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mm/khugepaged: minor reorderings in collapse_shmem()
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Several cleanups in collapse_shmem(): most of which probably do not
really matter, beyond doing things in a more familiar and reassuring
order.  Simplify the failure gotos in the main loop, and on success
update stats while interrupts still disabled from the last iteration.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261526400.2275@eggly.anvils
Fixes: f3f0e1d ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Hugh Dickins authored and Linus Torvalds committed Nov 30, 2018
1 parent 2af8ff2 commit 042a308
Showing 1 changed file with 32 additions and 40 deletions.
72 changes: 32 additions & 40 deletions mm/khugepaged.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1329,10 +1329,10 @@ static void collapse_shmem(struct mm_struct *mm,
goto out;
}

__SetPageLocked(new_page);
__SetPageSwapBacked(new_page);
new_page->index = start;
new_page->mapping = mapping;
__SetPageSwapBacked(new_page);
__SetPageLocked(new_page);
BUG_ON(!page_ref_freeze(new_page, 1));

/*
Expand Down Expand Up @@ -1366,13 +1366,13 @@ static void collapse_shmem(struct mm_struct *mm,
if (index == start) {
if (!xas_next_entry(&xas, end - 1)) {
result = SCAN_TRUNCATED;
break;
goto xa_locked;
}
xas_set(&xas, index);
}
if (!shmem_charge(mapping->host, 1)) {
result = SCAN_FAIL;
break;
goto xa_locked;
}
xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
nr_none++;
Expand All @@ -1387,13 +1387,12 @@ static void collapse_shmem(struct mm_struct *mm,
result = SCAN_FAIL;
goto xa_unlocked;
}
xas_lock_irq(&xas);
xas_set(&xas, index);
} else if (trylock_page(page)) {
get_page(page);
xas_unlock_irq(&xas);
} else {
result = SCAN_PAGE_LOCK;
break;
goto xa_locked;
}

/*
Expand All @@ -1408,11 +1407,10 @@ static void collapse_shmem(struct mm_struct *mm,
result = SCAN_TRUNCATED;
goto out_unlock;
}
xas_unlock_irq(&xas);

if (isolate_lru_page(page)) {
result = SCAN_DEL_PAGE_LRU;
goto out_isolate_failed;
goto out_unlock;
}

if (page_mapped(page))
Expand All @@ -1432,7 +1430,9 @@ static void collapse_shmem(struct mm_struct *mm,
*/
if (!page_ref_freeze(page, 3)) {
result = SCAN_PAGE_COUNT;
goto out_lru;
xas_unlock_irq(&xas);
putback_lru_page(page);
goto out_unlock;
}

/*
Expand All @@ -1444,24 +1444,26 @@ static void collapse_shmem(struct mm_struct *mm,
/* Finally, replace with the new page. */
xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
continue;
out_lru:
xas_unlock_irq(&xas);
putback_lru_page(page);
out_isolate_failed:
unlock_page(page);
put_page(page);
goto xa_unlocked;
out_unlock:
unlock_page(page);
put_page(page);
break;
goto xa_unlocked;
}
xas_unlock_irq(&xas);

__inc_node_page_state(new_page, NR_SHMEM_THPS);
if (nr_none) {
struct zone *zone = page_zone(new_page);

__mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
__mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
}

xa_locked:
xas_unlock_irq(&xas);
xa_unlocked:

if (result == SCAN_SUCCEED) {
struct page *page, *tmp;
struct zone *zone = page_zone(new_page);

/*
* Replacing old pages with new one has succeeded, now we
Expand All @@ -1476,11 +1478,11 @@ static void collapse_shmem(struct mm_struct *mm,
copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
page);
list_del(&page->lru);
unlock_page(page);
page_ref_unfreeze(page, 1);
page->mapping = NULL;
page_ref_unfreeze(page, 1);
ClearPageActive(page);
ClearPageUnevictable(page);
unlock_page(page);
put_page(page);
index++;
}
Expand All @@ -1489,28 +1491,17 @@ static void collapse_shmem(struct mm_struct *mm,
index++;
}

local_irq_disable();
__inc_node_page_state(new_page, NR_SHMEM_THPS);
if (nr_none) {
__mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
__mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
}
local_irq_enable();

/*
* Remove pte page tables, so we can re-fault
* the page as huge.
*/
retract_page_tables(mapping, start);

/* Everything is ready, let's unfreeze the new_page */
set_page_dirty(new_page);
SetPageUptodate(new_page);
page_ref_unfreeze(new_page, HPAGE_PMD_NR);
set_page_dirty(new_page);
mem_cgroup_commit_charge(new_page, memcg, false, true);
lru_cache_add_anon(new_page);
unlock_page(new_page);

/*
* Remove pte page tables, so we can re-fault the page as huge.
*/
retract_page_tables(mapping, start);
*hpage = NULL;

khugepaged_pages_collapsed++;
Expand Down Expand Up @@ -1543,8 +1534,8 @@ static void collapse_shmem(struct mm_struct *mm,
xas_store(&xas, page);
xas_pause(&xas);
xas_unlock_irq(&xas);
putback_lru_page(page);
unlock_page(page);
putback_lru_page(page);
xas_lock_irq(&xas);
}
VM_BUG_ON(nr_none);
Expand All @@ -1553,9 +1544,10 @@ static void collapse_shmem(struct mm_struct *mm,
/* Unfreeze new_page, caller would take care about freeing it */
page_ref_unfreeze(new_page, 1);
mem_cgroup_cancel_charge(new_page, memcg, true);
unlock_page(new_page);
new_page->mapping = NULL;
}

unlock_page(new_page);
out:
VM_BUG_ON(!list_empty(&pagelist));
/* TODO: tracepoints */
Expand Down

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