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Junxiao Bi 40b5e3f544 ocfs2: issue zeroout to EOF blocks 
commit 9449ad33be upstream.

For punch holes in EOF blocks, fallocate used buffer write to zero the
EOF blocks in last cluster.  But since ->writepage will ignore EOF
pages, those zeros will not be flushed.

This "looks" ok as commit 6bba4471f0 ("ocfs2: fix data corruption by
fallocate") will zero the EOF blocks when extend the file size, but it
isn't.  The problem happened on those EOF pages, before writeback, those
pages had DIRTY flag set and all buffer_head in them also had DIRTY flag
set, when writeback run by write_cache_pages(), DIRTY flag on the page
was cleared, but DIRTY flag on the buffer_head not.

When next write happened to those EOF pages, since buffer_head already
had DIRTY flag set, it would not mark page DIRTY again.  That made
writeback ignore them forever.  That will cause data corruption.  Even
directio write can't work because it will fail when trying to drop pages
caches before direct io, as it found the buffer_head for those pages
still had DIRTY flag set, then it will fall back to buffer io mode.

To make a summary of the issue, as writeback ingores EOF pages, once any
EOF page is generated, any write to it will only go to the page cache,
it will never be flushed to disk even file size extends and that page is
not EOF page any more.  The fix is to avoid zero EOF blocks with buffer
write.

The following code snippet from qemu-img could trigger the corruption.

  656   open("6b3711ae-3306-4bdd-823c-cf1c0060a095.conv.2", O_RDWR|O_DIRECT|O_CLOEXEC) = 11
  ...
  660   fallocate(11, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, 2275868672, 327680 <unfinished ...>
  660   fallocate(11, 0, 2275868672, 327680) = 0
  658   pwrite64(11, "

Link: https://lkml.kernel.org/r/20210722054923.24389-2-junxiao.bi@oracle.com
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.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>
2021-08-04 12:23:45 +02:00
arch x86/kvm: fix vcpu-id indexed array sizes 2021-08-04 12:23:44 +02:00
block blk-wbt: make sure throttle is enabled properly 2021-07-20 16:15:48 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 09:39:44 +01:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-20 16:15:44 +02:00
Documentation clocksource: Retry clock read if long delays detected 2021-07-20 16:15:46 +02:00
drivers virtio_net: Do not pull payload in skb->head 2021-08-04 12:23:44 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs ocfs2: issue zeroout to EOF blocks 2021-08-04 12:23:45 +02:00
include gro: ensure frag0 meets IP header alignment 2021-08-04 12:23:44 +02:00
init pid: take a reference when initializing cad_pid 2021-06-10 13:24:06 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:18:40 +02:00
kernel workqueue: fix UAF in pwq_unbound_release_workfn() 2021-07-31 08:22:37 +02:00
lib lib/decompress_unlz4.c: correctly handle zero-padding around initrds. 2021-07-20 16:16:10 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm: slab: fix kmem_cache_create failed when sysfs node not destroyed 2021-07-28 11:13:44 +02:00
net gro: ensure frag0 meets IP header alignment 2021-08-04 12:23:44 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-20 16:15:51 +02:00
scripts kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set 2021-07-28 11:13:43 +02:00
security smackfs: restrict bytes count in smk_set_cipso() 2021-07-20 16:16:06 +02:00
sound ALSA: sb: Fix potential ABBA deadlock in CSP driver 2021-07-28 11:13:49 +02:00
tools selftest: fix build error in tools/testing/selftests/vm/userfaultfd.c 2021-07-31 08:22:37 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped() 2021-07-28 11:13:51 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-09-26 18:01:31 +02:00
Makefile Linux 4.19.200 2021-07-31 08:22:38 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.