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Hugh Dickins 94ab10dd42 mm: delete unsafe BUG from page_cache_add_speculative() 
It is not easily reproducible, but on 5.16-rc I have several times hit
the VM_BUG_ON_PAGE(PageTail(page), page) in
page_cache_add_speculative(): usually from filemap_get_read_batch() for
an ext4 read, yesterday from next_uptodate_page() from
filemap_map_pages() for a shmem fault.

That BUG used to be placed where page_ref_add_unless() had succeeded,
but now it is placed before folio_ref_add_unless() is attempted: that is
not safe, since it is only the acquired reference which makes the page
safe from racing THP collapse or split.

We could keep the BUG, checking PageTail only when
folio_ref_try_add_rcu() has succeeded; but I don't think it adds much
value - just delete it.

Link: https://lkml.kernel.org/r/8b98fc6f-3439-8614-c3f3-945c659a1aba@google.com
Fixes: 020853b6f5 ("mm: Add folio_try_get_rcu()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-12-25 12:20:55 -08:00
arch parisc architecture late bug fixes for kernel v5.16 2021-12-22 10:17:16 -08:00
block block-5.16-2021-12-19 2021-12-19 12:38:53 -08:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Update to zstd-1.4.10 2021-11-13 15:32:30 -08:00
Documentation * Fix for compilation of selftests on non-x86 architectures 2021-12-21 12:25:57 -08:00
drivers Fix some IPMI crashes 2021-12-22 10:11:17 -08:00
fs Fixes: 2021-12-21 12:02:36 -08:00
include mm: delete unsafe BUG from page_cache_add_speculative() 2021-12-25 12:20:55 -08:00
init kbuild: Fix -Wimplicit-fallthrough=5 error for GCC 5.x and 6.x 2021-11-14 18:59:49 -08:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-20 10:35:54 -08:00
kernel kernel/crash_core: suppress unknown crashkernel parameter warning 2021-12-25 12:20:55 -08:00
lib Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2021-12-08 16:06:44 -08:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm, hwpoison: fix condition in free hugetlb page path 2021-12-25 12:20:55 -08:00
net Networking fixes for 5.16-rc6, including fixes from mac80211, wifi, bpf. 2021-12-16 15:02:14 -08:00
samples ftrace/samples: Add module to test multi direct modify interface 2021-12-09 13:02:44 -05:00
scripts recordmcount.pl: look for jgnop instruction as well as bcrl on s390 2021-12-12 18:52:26 +01:00
security Two overhead reduction patches for testing/fuzzing environment. 2021-12-22 10:06:32 -08:00
sound sound fixes for 5.16-rc5 2021-12-10 11:43:00 -08:00
tools * Fix for compilation of selftests on non-x86 architectures 2021-12-21 12:25:57 -08:00
usr initramfs: Check timestamp to prevent broken cpio archive 2021-10-24 13:48:40 +09:00
virt KVM: downgrade two BUG_ONs to WARN_ON_ONCE 2021-11-26 06:43:28 -05:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address for Guo Ren 2021-12-10 17:10:55 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 MAINTAINERS: mark more list instances as moderated 2021-12-25 12:20:55 -08:00
Makefile Linux 5.16-rc6 2021-12-19 14:14:33 -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.