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Alexander Zhu b0c582233a btrfs: fix alignment of VMA for memory mapped files on THP 
With CONFIG_READ_ONLY_THP_FOR_FS, the Linux kernel supports using THPs for
read-only mmapped files, such as shared libraries. However, the kernel
makes no attempt to actually align those mappings on 2MB boundaries,
which makes it impossible to use those THPs most of the time. This issue
applies to general file mapping THP as well as existing setups using
CONFIG_READ_ONLY_THP_FOR_FS. This is easily fixed by using
thp_get_unmapped_area for the unmapped_area function in btrfs, which
is what ext2, ext4, fuse, and xfs all use.

Initially btrfs had been left out in commit 8c07fc452ac0 ("btrfs: fix
alignment of VMA for memory mapped files on THP") as btrfs does not support
DAX. However, commit 1854bc6e24 ("mm/readahead: Align file mappings
for non-DAX") removed the DAX requirement. We should now be able to call
thp_get_unmapped_area() for btrfs.

The problem can be seen in /proc/PID/smaps where THPeligible is set to 0
on mappings to eligible shared object files as shown below.

Before this patch:

  7fc6a7e18000-7fc6a80cc000 r-xp 00000000 00:1e 199856
  /usr/lib64/libcrypto.so.1.1.1k
  Size:               2768 kB
  THPeligible:    0
  VmFlags: rd ex mr mw me

With this patch the library is mapped at a 2MB aligned address:

  fbdfe200000-7fbdfe4b4000 r-xp 00000000 00:1e 199856
  /usr/lib64/libcrypto.so.1.1.1k
  Size:               2768 kB
  THPeligible:    1
  VmFlags: rd ex mr mw me

This fixes the alignment of VMAs for any mmap of a file that has the
rd and ex permissions and size >= 2MB. The VMA alignment and
THPeligible field for anonymous memory is handled separately and
is thus not effected by this change.

CC: stable@vger.kernel.org # 5.18+
Signed-off-by: Alexander Zhu <alexlzhu@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26 12:27:53 +02:00
arch arm64 fixes for -rc7 2022-09-23 15:28:51 -07:00
block block-6.0-2022-09-22 2022-09-24 08:22:53 -07:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto crypto: blake2b: effectively disable frame size warning 2022-08-10 17:59:11 -07:00
Documentation I2C driver bugfixes for mlxbf and imx, a few documentation fixes after 2022-09-25 08:44:46 -07:00
drivers dax-and-nvdimm-fixes-v6.0-final 2022-09-25 08:53:52 -07:00
fs btrfs: fix alignment of VMA for memory mapped files on THP 2022-09-26 12:27:53 +02:00
include TTY/Serial driver fixes for 6.0-rc7 2022-09-24 08:42:55 -07:00
init arm64 fixes for -rc3 2022-08-26 11:32:53 -07:00
io_uring io_uring-6.0-2022-09-23 2022-09-24 08:27:08 -07:00
ipc Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
kernel Cgroup fixes for v6.0-rc6 2022-09-24 08:36:10 -07:00
lib Makefile.debug: re-enable debug info for .S files 2022-09-24 11:19:19 +09:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm slab fixes for 6.0-rc7 2022-09-22 14:37:58 -07:00
net Including fixes from wifi, netfilter and can. 2022-09-22 10:58:13 -07:00
samples Tracing updates for 5.20 / 6.0 2022-08-05 09:41:12 -07:00
scripts Makefile.debug: re-enable debug info for .S files 2022-09-24 11:19:19 +09:00
security Landlock fix for v6.0-rc4 2022-09-02 15:24:08 -07:00
sound Revert "ALSA: usb-audio: Split endpoint setups for hw_params and prepare" 2022-09-20 13:40:18 +02:00
tools dax-and-nvdimm-fixes-v6.0-final 2022-09-25 08:53:52 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Drop unnecessary initialization of "ops" in kvm_ioctl_create_device() 2022-08-19 04:05:43 -04:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap Devicetree fixes for v6.0, take 2: 2022-09-14 10:22:39 +01:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS I2C driver bugfixes for mlxbf and imx, a few documentation fixes after 2022-09-25 08:44:46 -07:00
Makefile Linux 6.0-rc7 2022-09-25 14:01:02 -07:00
README

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.