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Filename Latest commit message Latest commit date
Hugh Dickins e045e9e79d mm/thp: fix page_vma_mapped_walk() if THP mapped by ptes
Running certain tests with a DEBUG_VM kernel would crash within hours,
on the total_mapcount BUG() in split_huge_page_to_list(), while trying
to free up some memory by punching a hole in a shmem huge page: split's
try_to_unmap() was unable to find all the mappings of the page (which,
on a !DEBUG_VM kernel, would then keep the huge page pinned in memory).

Crash dumps showed two tail pages of a shmem huge page remained mapped
by pte: ptes in a non-huge-aligned vma of a gVisor process, at the end
of a long unmapped range; and no page table had yet been allocated for
the head of the huge page to be mapped into.

Although designed to handle these odd misaligned huge-page-mapped-by-pte
cases, page_vma_mapped_walk() falls short by returning false prematurely
when !pmd_present or !pud_present or !p4d_present or !pgd_present: there
are cases when a huge page may span the boundary, with ptes present in
the next.

Restructure page_vma_mapped_walk() as a loop to continue in these cases,
while keeping its layout much as before.  Add a step_forward() helper to
advance pvmw->address across those boundaries: originally I tried to use
mm's standard p?d_addr_end() macros, but hit the same crash 512 times
less often: because of the way redundant levels are folded together, but
folded differently in different configurations, it was just too
difficult to use them correctly; and step_forward() is simpler anyway.

Link: https://lkml.kernel.org/r/fedb8632-1798-de42-f39e-873551d5bc81@google.com
Fixes: ace71a19ce ("mm: introduce page_vma_mapped_walk()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Wang Yugui <wangyugui@e16-tech.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-06-30 08:47:54 -04:00
arch PCI: Add AMD RS690 quirk to enable 64-bit DMA 2021-06-30 08:47:49 -04:00
block blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-19 10:08:30 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 10:26:29 +01:00
crypto crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS 2021-05-11 14:04:15 +02:00
Documentation mm/slub: clarify verification reporting 2021-06-23 14:41:30 +02:00
drivers i2c: robotfuzz-osif: fix control-request directions 2021-06-30 08:47:50 -04:00
fs nilfs2: fix memory leak in nilfs_sysfs_delete_device_group 2021-06-30 08:47:50 -04:00
include mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page() 2021-06-30 08:47:53 -04:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel kthread: prevent deadlock when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync() 2021-06-30 08:47:51 -04:00
lib lib/lz4: explicitly support in-place decompression 2021-06-10 13:37:16 +02:00
LICENSES
mm mm/thp: fix page_vma_mapped_walk() if THP mapped by ptes 2021-06-30 08:47:54 -04:00
net net/packet: annotate accesses to po->ifindex 2021-06-30 08:47:48 -04:00
samples samples: vfio-mdev: fix error handing in mdpy_fb_probe() 2021-06-10 13:37:03 +02:00
scripts recordmcount: Correct st_shndx handling 2021-06-30 08:47:49 -04:00
security security: commoncap: fix -Wstringop-overread warning 2021-05-11 14:04:16 +02:00
sound ASoC: rt5659: Fix the lost powers for the HDA header 2021-06-23 14:41:27 +02:00
tools KVM: selftests: Fix kvm_check_cap() assertion 2021-06-30 08:47:49 -04:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: do not allow mapping valid but non-reference-counted pages 2021-06-30 08:47:50 -04:00
.clang-format
.cocciconfig
.get_maintainer.ignore
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.gitignore
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COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.128 2021-06-23 14:41:32 +02:00
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.