On Sun, Jan 19, 2020 at 04:15:02PM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 97d3d0f9a1cf132c63c0b8b8bd497b8a56283dd9 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Date: Mon, 13 Jan 2020 16:29:10 -0800
Subject: [PATCH] mm/huge_memory.c: thp: fix conflict of above-47bit hint
address and PMD alignment
Patch series "Fix two above-47bit hint address vs. THP bugs".
The two get_unmapped_area() implementations have to be fixed to provide
THP-friendly mappings if above-47bit hint address is specified.
This patch (of 2):
Filesystems use thp_get_unmapped_area() to provide THP-friendly
mappings. For DAX in particular.
Normally, the kernel doesn't create userspace mappings above 47-bit,
even if the machine allows this (such as with 5-level paging on x86-64).
Not all user space is ready to handle wide addresses. It's known that
at least some JIT compilers use higher bits in pointers to encode their
information.
Userspace can ask for allocation from full address space by specifying
hint address (with or without MAP_FIXED) above 47-bits. If the
application doesn't need a particular address, but wants to allocate
from whole address space it can specify -1 as a hint address.
Unfortunately, this trick breaks thp_get_unmapped_area(): the function
would not try to allocate PMD-aligned area if *any* hint address
specified.
Modify the routine to handle it correctly:
- Try to allocate the space at the specified hint address with length
padding required for PMD alignment.
- If failed, retry without length padding (but with the same hint
address);
- If the returned address matches the hint address return it.
- Otherwise, align the address as required for THP and return.
The user specified hint address is passed down to get_unmapped_area() so
above-47bit hint address will be taken into account without breaking
alignment requirements.
Link: http://lkml.kernel.org/r/20191220142548.7118-2-kirill.shutemov@xxxxxxxxxxxxxxx
Fixes: b569bab78d8d ("x86/mm: Prepare to expose larger address space to userspace")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Thomas Willhalm <thomas.willhalm@xxxxxxxxx>
Tested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: "Bruggeman, Otto G" <otto.g.bruggeman@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Conflict due to missing b3b07077b01e ("mm/huge_memory.c: make
__thp_get_unmapped_area static"), I've just queued both for 4.19 and
4.14.
--
Thanks,
Sasha
