From: Song Liu <songliubraving@fb.com>
To: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<akpm@linux-foundation.org>
Cc: <matthew.wilcox@oracle.com>, <kernel-team@fb.com>,
<william.kucharski@oracle.com>, <kirill.shutemov@linux.intel.com>,
Song Liu <songliubraving@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Hugh Dickins <hughd@google.com>
Subject: [PATCH v3] mm,thp: recheck each page before collapsing file THP
Date: Fri, 18 Oct 2019 11:03:45 -0700 [thread overview]
Message-ID: <20191018180345.4188310-1-songliubraving@fb.com> (raw)
In collapse_file(), after locking the page, it is necessary to recheck
that the page is up-to-date. Add PageUptodate() check for both shmem THP
and file THP.
Current khugepaged should not try to collapse dirty file THP, because it
is limited to read only text. Add a PageDirty check and warning for file
THP. This is added after page_mapping() check, because if the page is
truncated, it might be dirty.
Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
Changes v1 => v2:
Rearrange the checks per feedback from Johannes, Rik, and Kirill.
Changes v2 => v3:
Remove redudant checks before trylock_page(). (Johannes)
---
mm/khugepaged.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 0a1b4b484ac5..e20bb9d3482d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1601,17 +1601,6 @@ static void collapse_file(struct mm_struct *mm,
result = SCAN_FAIL;
goto xa_unlocked;
}
- } else if (!PageUptodate(page)) {
- xas_unlock_irq(&xas);
- wait_on_page_locked(page);
- if (!trylock_page(page)) {
- result = SCAN_PAGE_LOCK;
- goto xa_unlocked;
- }
- get_page(page);
- } else if (PageDirty(page)) {
- result = SCAN_FAIL;
- goto xa_locked;
} else if (trylock_page(page)) {
get_page(page);
xas_unlock_irq(&xas);
@@ -1626,7 +1615,12 @@ static void collapse_file(struct mm_struct *mm,
* without racing with truncate.
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);
- VM_BUG_ON_PAGE(!PageUptodate(page), page);
+
+ /* double check the page is up to date */
+ if (unlikely(!PageUptodate(page))) {
+ result = SCAN_FAIL;
+ goto out_unlock;
+ }
/*
* If file was truncated then extended, or hole-punched, before
@@ -1642,6 +1636,15 @@ static void collapse_file(struct mm_struct *mm,
goto out_unlock;
}
+ /*
+ * khugepaged should not try to collapse dirty pages for
+ * file THP. Show warning if this somehow happens.
+ */
+ if (WARN_ON_ONCE(!is_shmem && PageDirty(page))) {
+ result = SCAN_FAIL;
+ goto out_unlock;
+ }
+
if (isolate_lru_page(page)) {
result = SCAN_DEL_PAGE_LRU;
goto out_unlock;
--
2.17.1
next reply other threads:[~2019-10-18 18:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 18:03 Song Liu [this message]
2019-10-19 1:17 ` [PATCH v3] mm,thp: recheck each page before collapsing file THP Andrew Morton
2019-10-19 5:24 ` Song Liu
2019-10-21 18:03 ` Johannes Weiner
2019-11-06 4:58 ` Andrew Morton
2019-11-06 5:45 ` Song Liu
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