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Junxiao Bi 9449ad33be ocfs2: issue zeroout to EOF blocks 
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>
2021-07-30 10:14:39 -07:00
arch ARM: 2021-07-29 09:42:09 -07:00
block block-5.14-2021-07-08 2021-07-09 12:05:33 -07:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-07-09 11:00:44 -07:00
Documentation ARM: 2021-07-29 09:42:09 -07:00
drivers platform-drivers-x86 for v5.14-2 2021-07-28 10:31:17 -07:00
fs ocfs2: issue zeroout to EOF blocks 2021-07-30 10:14:39 -07:00
include dmaengine: idxd: Change license on idxd.h to LGPL 2021-07-28 10:22:43 -07:00
init Revert "mm/slub: use stackdepot to save stack trace in objects" 2021-07-17 13:27:00 -07:00
ipc Merge branch 'akpm' (patches from Andrew) 2021-07-02 12:08:10 -07:00
kernel Merge branch 'for-5.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2021-07-27 14:02:57 -07:00
lib lib/test_string.c: move string selftest in the Runtime Testing menu 2021-07-30 10:14:39 -07:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm: fix the deadlock in finish_fault() 2021-07-23 17:43:28 -07:00
net af_unix: fix garbage collect vs MSG_PEEK 2021-07-28 10:18:00 -07:00
samples Networking fixes for 5.14-rc2, including fixes from bpf and netfilter. 2021-07-14 09:24:32 -07:00
scripts Kbuild fixes for v5.14 2021-07-18 11:10:30 -07:00
security asm-generic/unaligned: Unify asm/unaligned.h around struct helper 2021-07-02 12:43:40 -07:00
sound sound fixes for 5.14-rc3 2021-07-23 09:58:23 -07:00
tools ARM: 2021-07-29 09:42:09 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: add missing compat KVM_CLEAR_DIRTY_LOG 2021-07-27 16:59:01 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 m68k updates for v5.14 2021-06-28 14:01:03 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -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 Char/Misc fixes for 5.14-rc3 2021-07-23 10:14:56 -07:00
Makefile Linux 5.14-rc3 2021-07-25 15:35:14 -07:00
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.