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Jan Kara 7ce2b16bad fs: Don't invalidate page buffers in block_write_full_page() commit `6dbf7bb555` upstream. If block_write_full_page() is called for a page that is beyond current inode size, it will truncate page buffers for the page and return 0. This logic has been added in 2.5.62 in commit 81eb69062588 ("fix ext3 BUG due to race with truncate") in history.git tree to fix a problem with ext3 in data=ordered mode. This particular problem doesn't exist anymore because ext3 is long gone and ext4 handles ordered data differently. Also normally buffers are invalidated by truncate code and there's no need to specially handle this in ->writepage() code. This invalidation of page buffers in block_write_full_page() is causing issues to filesystems (e.g. ext4 or ocfs2) when block device is shrunk under filesystem's hands and metadata buffers get discarded while being tracked by the journalling layer. Although it is obviously "not supported" it can cause kernel crashes like: [ 7986.689400] BUG: unable to handle kernel NULL pointer dereference at +0000000000000008 [ 7986.697197] PGD 0 P4D 0 [ 7986.699724] Oops: 0002 [#1] SMP PTI [ 7986.703200] CPU: 4 PID: 203778 Comm: jbd2/dm-3-8 Kdump: loaded Tainted: G +O --------- - - 4.18.0-147.5.0.5.h126.eulerosv2r9.x86_64 #1 [ 7986.716438] Hardware name: Huawei RH2288H V3/BC11HGSA0, BIOS 1.57 08/11/2015 [ 7986.723462] RIP: 0010:jbd2_journal_grab_journal_head+0x1b/0x40 [jbd2] ... [ 7986.810150] Call Trace: [ 7986.812595] __jbd2_journal_insert_checkpoint+0x23/0x70 [jbd2] [ 7986.818408] jbd2_journal_commit_transaction+0x155f/0x1b60 [jbd2] [ 7986.836467] kjournald2+0xbd/0x270 [jbd2] which is not great. The crash happens because bh->b_private is suddently NULL although BH_JBD flag is still set (this is because block_invalidatepage() cleared BH_Mapped flag and subsequent bh lookup found buffer without BH_Mapped set, called init_page_buffers() which has rewritten bh->b_private). So just remove the invalidation in block_write_full_page(). Note that the buffer cache invalidation when block device changes size is already careful to avoid similar problems by using invalidate_mapping_pages() which skips busy buffers so it was only this odd block_write_full_page() behavior that could tear down bdev buffers under filesystem's hands. Reported-by: Ye Bin <yebin10@huawei.com> Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> CC: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-11-05 11:08:46 +01:00
arch	perf/x86/amd/ibs: Fix raw sample data accumulation	2020-11-05 11:08:46 +01:00
block	Revert "block: ratelimit handle_bad_sector() message"	2020-11-05 11:08:35 +01:00
certs	export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()	2018-08-22 23:21:44 +09:00
crypto	crypto: algif_skcipher - EBUSY on aio should be an error	2020-10-29 09:55:01 +01:00
Documentation	media: videodev2.h: RGB BT2020 and HSV are always full range	2020-11-05 11:08:40 +01:00
drivers	media: uvcvideo: Fix uvc_ctrl_fixup_xu_info() not having any effect	2020-11-05 11:08:46 +01:00
firmware	Fix built-in early-load Intel microcode alignment	2020-01-23 08:21:29 +01:00
fs	fs: Don't invalidate page buffers in block_write_full_page()	2020-11-05 11:08:46 +01:00
include	usb: typec: tcpm: During PR_SWAP, source caps should be sent only after tSwapSourceStart	2020-11-05 11:08:40 +01:00
init	printk: reduce LOG_BUF_SHIFT range for H8300	2020-11-05 11:08:41 +01:00
ipc	ipc/util.c: sysvipc_find_ipc() incorrectly updates position index	2020-05-20 08:18:40 +02:00
kernel	kgdb: Make "kgdbcon" work properly with "kgdb_earlycon"	2020-11-05 11:08:41 +01:00
lib	sgl_alloc_order: fix memory leak	2020-11-05 11:08:45 +01:00
LICENSES	LICENSES: Remove CC-BY-SA-4.0 license text	2018-10-18 11:28:50 +02:00
mm	mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary	2020-10-29 09:55:15 +01:00
net	net: 9p: initialize sun_server.sun_path to have addr's value only when addr is valid	2020-11-05 11:08:44 +01:00
samples	misc: vop: add round_up(x,4) for vring_size to avoid kernel panic	2020-10-30 10:38:29 +01:00
scripts	scripts/setlocalversion: make git describe output more reliable	2020-11-05 11:08:31 +01:00
security	evm: Check size of security.evm before using it	2020-11-05 11:08:34 +01:00
sound	ALSA: seq: oss: Avoid mutex lock for a long-time ioctl	2020-10-29 09:55:11 +01:00
tools	bpf: Fix comment for helper bpf_current_task_under_cgroup()	2020-11-05 11:08:34 +01:00
usr	initramfs: restore default compression behavior	2020-04-13 10:44:59 +02:00
virt	KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch	2020-10-01 13:14:54 +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 4.19.154	2020-10-30 10:38:33 +01:00
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.