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Chris Mason 53aaa9f1a6 Btrfs: keep pages dirty when using btrfs_writepage_fixup_worker 
[ Upstream commit 25f3c50219 ]

For COW, btrfs expects pages dirty pages to have been through a few setup
steps.  This includes reserving space for the new block allocations and marking
the range in the state tree for delayed allocation.

A few places outside btrfs will dirty pages directly, especially when unmapping
mmap'd pages.  In order for these to properly go through COW, we run them
through a fixup worker to wait for stable pages, and do the delalloc prep.

87826df0ec added a window where the dirty pages were cleaned, but pending
more action from the fixup worker.  We clear_page_dirty_for_io() before
we call into writepage, so the page is no longer dirty.  The commit
changed it so now we leave the page clean between unlocking it here and
the fixup worker starting at some point in the future.

During this window, page migration can jump in and relocate the page.  Once our
fixup work actually starts, it finds page->mapping is NULL and we end up
freeing the page without ever writing it.

This leads to crc errors and other exciting problems, since it screws up the
whole statemachine for waiting for ordered extents.  The fix here is to keep
the page dirty while we're waiting for the fixup worker to get to work.
This is accomplished by returning -EAGAIN from btrfs_writepage_cow_fixup
if we queued the page up for fixup, which will cause the writepage
function to redirty the page.

Because we now expect the page to be dirty once it gets to the fixup
worker we must adjust the error cases to call clear_page_dirty_for_io()
on the page.  That is the bulk of the patch, but it is not the fix, the
fix is the -EAGAIN from btrfs_writepage_cow_fixup.  We cannot separate
these two changes out because the error conditions change with the new
expectations.

Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-02-24 08:36:31 +01:00
arch KVM: s390: ENOTSUPP -> EOPNOTSUPP fixups 2020-02-24 08:36:31 +01:00
block block: fix memleak of bio integrity data 2020-01-26 10:01:09 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: testmgr - don't try to decrypt uninitialized buffers 2020-02-14 16:34:18 -05:00
Documentation dt-bindings: iio: adc: ad7606: Fix wrong maxItems value 2020-02-14 16:34:19 -05:00
drivers nbd: add a flush_workqueue in nbd_start_device 2020-02-24 08:36:31 +01:00
fs Btrfs: keep pages dirty when using btrfs_writepage_fixup_worker 2020-02-24 08:36:31 +01:00
include raid6/test: fix a compilation error 2020-02-24 08:36:27 +01:00
init Revert "um: Enable CONFIG_CONSTRUCTORS" 2020-02-01 09:34:53 +00:00
ipc ipc/msg.c: consolidate all xxxctl_down() functions 2020-02-11 04:35:07 -08:00
kernel tracing: Simplify assignment parsing for hist triggers 2020-02-24 08:36:31 +01:00
lib lib/test_kasan.c: fix memory leak in kmalloc_oob_krealloc_more() 2020-02-11 04:35:14 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush 2020-02-11 04:35:42 -08:00
net net/sched: flower: add missing validation of TCA_FLOWER_FLAGS 2020-02-24 08:36:22 +01:00
samples samples/bpf: Xdp_redirect_cpu fix missing tracepoint attach 2020-02-11 04:35:29 -08:00
scripts scripts/find-unused-docs: Fix massive false positives 2020-02-11 04:35:23 -08:00
security selinux: fall back to ref-walk if audit is required 2020-02-14 16:34:20 -05:00
sound ALSA: ctl: allow TLV read operation for callback type of element in locked case 2020-02-24 08:36:24 +01:00
tools selftests: settings: tests can be in subsubdirs 2020-02-24 08:36:30 +01:00
usr gen_initramfs_list.sh: fix 'bad variable name' error 2020-01-09 10:20:00 +01:00
virt KVM: arm64: Treat emulated TVAL TimerValue as a signed 32-bit integer 2020-02-14 16:34:18 -05:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: correct entries for ISDN/mISDN section 2020-02-11 04:35:06 -08:00
Makefile Linux 5.4.21 2020-02-19 19:53:10 +01:00
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.