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

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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>
This commit is contained in:
Song Liu 2019-11-30 17:57:19 -08:00 committed by Linus Torvalds
parent f1fe80d4ae
commit 75f360696c
1 changed files with 18 additions and 0 deletions
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18
mm/khugepaged.c
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@ -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);