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Ryan Roberts 96204e1531 mm: thp_get_unmapped_area must honour topdown preference 
The addition of commit efa7df3e3b ("mm: align larger anonymous mappings
on THP boundaries") caused the "virtual_address_range" mm selftest to
start failing on arm64.  Let's fix that regression.

There were 2 visible problems when running the test; 1) it takes much
longer to execute, and 2) the test fails.  Both are related:

The (first part of the) test allocates as many 1GB anonymous blocks as it
can in the low 256TB of address space, passing NULL as the addr hint to
mmap.  Before the faulty patch, all allocations were abutted and contained
in a single, merged VMA.  However, after this patch, each allocation is in
its own VMA, and there is a 2M gap between each VMA.  This causes the 2
problems in the test: 1) mmap becomes MUCH slower because there are so
many VMAs to check to find a new 1G gap.  2) mmap fails once it hits the
VMA limit (/proc/sys/vm/max_map_count).  Hitting this limit then causes a
subsequent calloc() to fail, which causes the test to fail.

The problem is that arm64 (unlike x86) selects
ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.  But __thp_get_unmapped_area()
allocates len+2M then always aligns to the bottom of the discovered gap. 
That causes the 2M hole.

Fix this by detecting cases where we can still achive the alignment goal
when moved to the top of the allocated area, if configured to prefer
top-down allocation.

While we are at it, fix thp_get_unmapped_area's use of pgoff, which should
always be zero for anonymous mappings.  Prior to the faulty change, while
it was possible for user space to pass in pgoff!=0, the old
mm->get_unmapped_area() handler would not use it.  thp_get_unmapped_area()
does use it, so let's explicitly zero it before calling the handler.  This
should also be the correct behavior for arches that define their own
get_unmapped_area() handler.

Link: https://lkml.kernel.org/r/20240123171420.3970220-1-ryan.roberts@arm.com
Fixes: efa7df3e3b ("mm: align larger anonymous mappings on THP boundaries")
Closes: https://lore.kernel.org/linux-mm/1e8f5ac7-54ce-433a-ae53-81522b2320e1@arm.com/
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-26 01:23:44 -08:00
arch scs: add CONFIG_MMU dependency for vfree_atomic() 2024-01-25 23:52:21 -08:00
block for-6.8/block-2024-01-18 2024-01-18 18:22:40 -08:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: scomp - fix req->dst buffer overflow 2023-12-29 11:25:56 +08:00
Documentation Updates for time and clocksources: 2024-01-21 11:14:40 -08:00
drivers Updates for time and clocksources: 2024-01-21 11:14:40 -08:00
fs fs/hugetlbfs/inode.c: mm/memory-failure.c: fix hugetlbfs hwpoison handling 2024-01-25 23:52:20 -08:00
include mm, kmsan: fix infinite recursion due to RCU critical section 2024-01-25 23:52:21 -08:00
init Driver core changes for 6.8-rc1 2024-01-18 09:48:40 -08:00
io_uring for-6.8/io_uring-2024-01-18 2024-01-18 18:17:57 -08:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel uprobes: use pagesize-aligned virtual address when replacing pages 2024-01-25 23:52:20 -08:00
lib stackdepot: make fast paths lock-less again 2024-01-25 23:52:21 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: thp_get_unmapped_area must honour topdown preference 2024-01-26 01:23:44 -08:00
net Assorted CephFS fixes and cleanups with nothing standing out. 2024-01-19 09:58:55 -08:00
rust Rust changes for v6.8 2024-01-11 13:05:41 -08:00
samples RISC-V Patches for the 6.8 Merge Window, Part 4 2024-01-20 11:06:04 -08:00
scripts Coccinelle change for v6.8 2024-01-20 14:20:34 -08:00
security + Features 2024-01-19 10:53:55 -08:00
sound sound fixes for 6.8-rc1 2024-01-19 12:30:29 -08:00
tools selftests/mm: ksm_tests should only MADV_HUGEPAGE valid memory 2024-01-25 23:52:21 -08:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt Generic: 2024-01-17 13:03:37 -08:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap Char/Misc and other Driver changes for 6.8-rc1 2024-01-17 16:47:17 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
Makefile Linux 6.8-rc1 2024-01-21 14:11:32 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.