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Message-Id: <20210628143004.32596-67-sashal@kernel.org>
Date: Mon, 28 Jun 2021 10:29:59 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Hugh Dickins <hughd@...gle.com>, Neel Natu <neelnatu@...gle.com>,
Matthew Wilcox <willy@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Zhang Yi <wetpzy@...il.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Mike Kravetz <mike.kravetz@...cle.com>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Darren Hart <dvhart@...radead.org>,
Davidlohr Bueso <dave@...olabs.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 5.4 66/71] mm, futex: fix shared futex pgoff on shmem huge page
From: Hugh Dickins <hughd@...gle.com>
[ Upstream commit fe19bd3dae3d15d2fbfdb3de8839a6ea0fe94264 ]
If more than one futex is placed on a shmem huge page, it can happen
that waking the second wakes the first instead, and leaves the second
waiting: the key's shared.pgoff is wrong.
When 3.11 commit 13d60f4b6ab5 ("futex: Take hugepages into account when
generating futex_key"), the only shared huge pages came from hugetlbfs,
and the code added to deal with its exceptional page->index was put into
hugetlb source. Then that was missed when 4.8 added shmem huge pages.
page_to_pgoff() is what others use for this nowadays: except that, as
currently written, it gives the right answer on hugetlbfs head, but
nonsense on hugetlbfs tails. Fix that by calling hugetlbfs-specific
hugetlb_basepage_index() on PageHuge tails as well as on head.
Yes, it's unconventional to declare hugetlb_basepage_index() there in
pagemap.h, rather than in hugetlb.h; but I do not expect anything but
page_to_pgoff() ever to need it.
[akpm@...ux-foundation.org: give hugetlb_basepage_index() prototype the correct scope]
Link: https://lkml.kernel.org/r/b17d946b-d09-326e-b42a-52884c36df32@google.com
Fixes: 800d8c63b2e9 ("shmem: add huge pages support")
Reported-by: Neel Natu <neelnatu@...gle.com>
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Zhang Yi <wetpzy@...il.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Darren Hart <dvhart@...radead.org>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Note on stable backport: leave redundant #include <linux/hugetlb.h>
in kernel/futex.c, to avoid conflict over the header files included.
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
include/linux/hugetlb.h | 16 ----------------
include/linux/pagemap.h | 13 +++++++------
kernel/futex.c | 2 +-
mm/hugetlb.c | 5 +----
4 files changed, 9 insertions(+), 27 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index fc717aeb2b3d..a0513c444446 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -469,17 +469,6 @@ static inline int hstate_index(struct hstate *h)
return h - hstates;
}
-pgoff_t __basepage_index(struct page *page);
-
-/* Return page->index in PAGE_SIZE units */
-static inline pgoff_t basepage_index(struct page *page)
-{
- if (!PageCompound(page))
- return page->index;
-
- return __basepage_index(page);
-}
-
extern int dissolve_free_huge_page(struct page *page);
extern int dissolve_free_huge_pages(unsigned long start_pfn,
unsigned long end_pfn);
@@ -695,11 +684,6 @@ static inline int hstate_index(struct hstate *h)
return 0;
}
-static inline pgoff_t basepage_index(struct page *page)
-{
- return page->index;
-}
-
static inline int dissolve_free_huge_page(struct page *page)
{
return 0;
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 37a4d9e32cd3..8543b1aaa529 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -397,7 +397,7 @@ static inline struct page *read_mapping_page(struct address_space *mapping,
}
/*
- * Get index of the page with in radix-tree
+ * Get index of the page within radix-tree (but not for hugetlb pages).
* (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
*/
static inline pgoff_t page_to_index(struct page *page)
@@ -416,15 +416,16 @@ static inline pgoff_t page_to_index(struct page *page)
return pgoff;
}
+extern pgoff_t hugetlb_basepage_index(struct page *page);
+
/*
- * Get the offset in PAGE_SIZE.
- * (TODO: hugepage should have ->index in PAGE_SIZE)
+ * Get the offset in PAGE_SIZE (even for hugetlb pages).
+ * (TODO: hugetlb pages should have ->index in PAGE_SIZE)
*/
static inline pgoff_t page_to_pgoff(struct page *page)
{
- if (unlikely(PageHeadHuge(page)))
- return page->index << compound_order(page);
-
+ if (unlikely(PageHuge(page)))
+ return hugetlb_basepage_index(page);
return page_to_index(page);
}
diff --git a/kernel/futex.c b/kernel/futex.c
index 375e7e98e301..f82879ae6577 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -737,7 +737,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, enum futex_a
key->both.offset |= FUT_OFF_INODE; /* inode-based key */
key->shared.i_seq = get_inode_sequence_number(inode);
- key->shared.pgoff = basepage_index(tail);
+ key->shared.pgoff = page_to_pgoff(tail);
rcu_read_unlock();
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index fe15e7d8220a..95a32749af4d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1461,15 +1461,12 @@ int PageHeadHuge(struct page *page_head)
return get_compound_page_dtor(page_head) == free_huge_page;
}
-pgoff_t __basepage_index(struct page *page)
+pgoff_t hugetlb_basepage_index(struct page *page)
{
struct page *page_head = compound_head(page);
pgoff_t index = page_index(page_head);
unsigned long compound_idx;
- if (!PageHuge(page_head))
- return page_index(page);
-
if (compound_order(page_head) >= MAX_ORDER)
compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
else
--
2.30.2
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