Commit 95feeabb authored Nov 30, 2018 by Hugh Dickins Committed by Linus Torvalds Nov 30, 2018

mm/khugepaged: fix the xas_create_range() error path

collapse_shmem()'s xas_nomem() is very unlikely to fail, but it is
rightly given a failure path, so move the whole xas_create_range() block
up before __SetPageLocked(new_page): so that it does not need to
remember to unlock_page(new_page).

Add the missing mem_cgroup_cancel_charge(), and set (currently unused)
result to SCAN_FAIL rather than SCAN_SUCCEED.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261531200.2275@eggly.anvils


Fixes: 77da9389 ("mm: Convert collapse_shmem to XArray")
Signed-off-by: Hugh Dickins <hughd@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 06a5e126

mm/khugepaged.c

+14 −11

Original line number	Diff line number	Diff line
		@@ -1329,6 +1329,20 @@ static void collapse_shmem(struct mm_struct *mm,
		goto out;
		}

		/* This will be less messy when we use multi-index entries */
		do {
		xas_lock_irq(&xas);
		xas_create_range(&xas);
		if (!xas_error(&xas))
		break;
		xas_unlock_irq(&xas);
		if (!xas_nomem(&xas, GFP_KERNEL)) {
		mem_cgroup_cancel_charge(new_page, memcg, true);
		result = SCAN_FAIL;
		goto out;
		}
		} while (1);

		__SetPageLocked(new_page);
		__SetPageSwapBacked(new_page);
		new_page->index = start;
		@@ -1340,17 +1354,6 @@ static void collapse_shmem(struct mm_struct *mm,
		* be able to map it or use it in another way until we unlock it.
		*/

		/* This will be less messy when we use multi-index entries */
		do {
		xas_lock_irq(&xas);
		xas_create_range(&xas);
		if (!xas_error(&xas))
		break;
		xas_unlock_irq(&xas);
		if (!xas_nomem(&xas, GFP_KERNEL))
		goto out;
		} while (1);

		xas_set(&xas, start);
		for (index = start; index < end; index++) {
		struct page *page = xas_next(&xas);

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