Commit 75f36069 authored Nov 30, 2019 by Song Liu Committed by Linus Torvalds Dec 01, 2019

mm/thp: flush file for !is_shmem PageDirty() case in collapse_file()

For non-shmem file THPs, khugepaged only collapses read only .text
mapping (VM_DENYWRITE).  These pages should not be dirty except the case
where the file hasn't been flushed since first write.

Call filemap_flush() in collapse_file() to accelerate the write back in
such cases.

Link: http://lkml.kernel.org/r/20191106060930.2571389-3-songliubraving@fb.com


Signed-off-by: Song Liu <songliubraving@fb.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f1fe80d4

mm/khugepaged.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -1602,6 +1602,24 @@ static void collapse_file(struct mm_struct *mm,
		result = SCAN_FAIL;
		goto xa_unlocked;
		}
		} else if (PageDirty(page)) {
		/*
		* khugepaged only works on read-only fd,
		* so this page is dirty because it hasn't
		* been flushed since first write. There
		* won't be new dirty pages.
		*
		* Trigger async flush here and hope the
		* writeback is done when khugepaged
		* revisits this page.
		*
		* This is a one-off situation. We are not
		* forcing writeback in loop.
		*/
		xas_unlock_irq(&xas);
		filemap_flush(mapping);
		result = SCAN_FAIL;
		goto xa_unlocked;
		} else if (trylock_page(page)) {
		get_page(page);
		xas_unlock_irq(&xas);

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