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Dave Chinner a837eca241 iomap: Revert "fs/iomap.c: get/put the page in iomap_page_create/release()" 
This reverts commit 61c6de6672.

The reverted commit added page reference counting to iomap page
structures that are used to track block size < page size state. This
was supposed to align the code with page migration page accounting
assumptions, but what it has done instead is break XFS filesystems.
Every fstests run I've done on sub-page block size XFS filesystems
has since picking up this commit 2 days ago has failed with bad page
state errors such as:

# ./run_check.sh "-m rmapbt=1,reflink=1 -i sparse=1 -b size=1k" "generic/038"
....
SECTION       -- xfs
FSTYP         -- xfs (debug)
PLATFORM      -- Linux/x86_64 test1 4.20.0-rc6-dgc+
MKFS_OPTIONS  -- -f -m rmapbt=1,reflink=1 -i sparse=1 -b size=1k /dev/sdc
MOUNT_OPTIONS -- /dev/sdc /mnt/scratch

generic/038 454s ...
 run fstests generic/038 at 2018-12-20 18:43:05
 XFS (sdc): Unmounting Filesystem
 XFS (sdc): Mounting V5 Filesystem
 XFS (sdc): Ending clean mount
 BUG: Bad page state in process kswapd0  pfn:3a7fa
 page:ffffea0000ccbeb0 count:0 mapcount:0 mapping:ffff88800d9b6360 index:0x1
 flags: 0xfffffc0000000()
 raw: 000fffffc0000000 dead000000000100 dead000000000200 ffff88800d9b6360
 raw: 0000000000000001 0000000000000000 00000000ffffffff
 page dumped because: non-NULL mapping
 CPU: 0 PID: 676 Comm: kswapd0 Not tainted 4.20.0-rc6-dgc+ #915
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-1 04/01/2014
 Call Trace:
  dump_stack+0x67/0x90
  bad_page.cold.116+0x8a/0xbd
  free_pcppages_bulk+0x4bf/0x6a0
  free_unref_page_list+0x10f/0x1f0
  shrink_page_list+0x49d/0xf50
  shrink_inactive_list+0x19d/0x3b0
  shrink_node_memcg.constprop.77+0x398/0x690
  ? shrink_slab.constprop.81+0x278/0x3f0
  shrink_node+0x7a/0x2f0
  kswapd+0x34b/0x6d0
  ? node_reclaim+0x240/0x240
  kthread+0x11f/0x140
  ? __kthread_bind_mask+0x60/0x60
  ret_from_fork+0x24/0x30
 Disabling lock debugging due to kernel taint
....

The failures are from anyway that frees pages and empties the
per-cpu page magazines, so it's not a predictable failure or an easy
to debug failure.

generic/038 is a reliable reproducer of this problem - it has a 9 in
10 failure rate on one of my test machines. Failure on other
machines have been at random points in fstests runs but every run
has ended up tripping this problem. Hence generic/038 was used to
bisect the failure because it was the most reliable failure.

It is too close to the 4.20 release (not to mention holidays) to
try to diagnose, fix and test the underlying cause of the problem,
so reverting the commit is the only option we have right now. The
revert has been tested against a current tot 4.20-rc7+ kernel across
multiple machines running sub-page block size XFs filesystems and
none of the bad page state failures have been seen.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Cc: Piotr Jaroszynski <pjaroszynski@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Brian Foster <bfoster@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-12-20 07:22:51 -08:00
arch kvm: x86: Add AMD's EX_CFG to the list of ignored MSRs 2018-12-18 22:15:44 +01:00
block block: Fix null_blk_zoned creation failure with small number of zones 2018-12-11 16:19:38 -07:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: user - Disable statistics interface 2018-12-07 13:56:08 +08:00
Documentation XArray updates for 4.20-rc7 2018-12-13 16:35:58 -08:00
drivers Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs iomap: Revert "fs/iomap.c: get/put the page in iomap_page_create/release()" 2018-12-20 07:22:51 -08:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
init psi: fix reference to kernel commandline enable 2018-12-14 15:05:45 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
lib XArray: Fix xa_alloc when id exceeds max 2018-12-13 14:07:33 -05:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm hugetlbfs: call VM_BUG_ON_PAGE earlier in free_huge_page() 2018-12-14 15:05:45 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
samples VFIO updates for v4.20 2018-10-31 11:01:38 -07:00
scripts scripts/spdxcheck.py: always open files in binary mode 2018-12-14 15:05:45 -08:00
security ima: cleanup the match_token policy code 2018-12-17 16:31:28 -08:00
sound ALSA: hda/realtek: Enable audio jacks of ASUS UX433FN/UX333FA with ALC294 2018-12-10 11:25:22 +01:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: fix unregistering coalesced mmio zone from wrong bus 2018-12-18 22:07:25 +01:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.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 mailmap: Update email for Punit Agrawal 2018-11-05 10:02:11 +00:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: update entry for MMP platform 2018-12-03 12:39:57 -08:00
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 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-19 23:34:33 -08:00
Makefile Linux 4.20-rc7 2018-12-16 15:46:55 -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.