linux-kernel - [PATCH v2 14/17] khugepaged: Reset scan address to correct alignment

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Message-Id: <20250211111326.14295-15-dev.jain@arm.com>
Date: Tue, 11 Feb 2025 16:43:23 +0530
From: Dev Jain <dev.jain@....com>
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	Dev Jain <dev.jain@....com>
Subject: [PATCH v2 14/17] khugepaged: Reset scan address to correct alignment

There are two situations:
1) After retaking the mmap lock, the next VMA expands downwards.
2) After khugepaged sleeps and starts again, it will pick up the starting address
   from the global struct khugepaged_scan, and hence will pick up the same VMA as
   in the previous cycle.

In both cases, khugepaged_scan.address > hstart. Therefore, explicitly align the
address to the order we are scanning for. Previously this was not a problem since
the alignment was to be always PMD-aligned.

Signed-off-by: Dev Jain <dev.jain@....com>
---
 mm/khugepaged.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e1c2c5b89f6d..7c9a758f6817 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2722,6 +2722,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
 		hstart = round_up(vma->vm_start, PAGE_SIZE << order);
 		if (khugepaged_scan.address < hstart)
 			khugepaged_scan.address = hstart;
+		else
+			khugepaged_scan.address = round_down(khugepaged_scan.address, PAGE_SIZE << order);
+
 		VM_BUG_ON(khugepaged_scan.address & ((PAGE_SIZE << order) - 1));
 
 		while (khugepaged_scan.address < hend) {
-- 
2.30.2