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Jens Axboe dbe3ece128 dm: don't reuse bio for flushes 
DM currently has a statically allocated bio that it uses to issue empty
flushes. It doesn't submit this bio, it just uses it for maintaining
state while setting up clones. Multiple users can access this bio at the
same time. This wasn't previously an issue, even if it was a bit iffy,
but with the blkg associations it can become one.

We setup the blkg association, then clone bio's and submit, then remove
the blkg assocation again. But since we can have multiple tasks doing
this at the same time, against multiple blkg's, then we can either lose
references to a blkg, or put it twice. The latter causes complaints on
the percpu ref being <= 0 when released, and can cause use-after-free as
well. Ming reports that xfstest generic/475 triggers this:

------------[ cut here ]------------
percpu ref (blkg_release) <= 0 (0) after switching to atomic
WARNING: CPU: 13 PID: 0 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x2c9/0x4a0

Switch to just using an on-stack bio for this, and get rid of the
embedded bio.

Fixes: 5cdf2e3fea ("blkcg: associate blkg when associating a device")
Reported-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-19 09:13:34 -07:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-09 15:12:33 -08:00
block block: make request_to_qc_t public 2018-12-18 17:50:47 +01:00
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 block: update sysfs documentation 2018-12-16 19:53:06 -07:00
drivers dm: don't reuse bio for flushes 2018-12-19 09:13:34 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Linux 4.20-rc6 2018-12-09 17:45:40 -07:00
include block: make request_to_qc_t public 2018-12-18 17:50:47 +01:00
init Linux 4.20-rc5 2018-12-04 09:38:05 -07:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel Linux 4.20-rc6 2018-12-09 17:45:40 -07:00
lib iov_iter: introduce hash_and_copy_to_iter helper 2018-12-13 09:58:54 +01:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm Linux 4.20-rc6 2018-12-09 17:45:40 -07:00
net datagram: introduce skb_copy_and_hash_datagram_iter helper 2018-12-13 09:58:55 +01:00
samples VFIO updates for v4.20 2018-10-31 11:01:38 -07:00
scripts Fixes for stackleak 2018-12-07 13:13:07 -08:00
security selinux/stable-4.20 PR 20181129 2018-11-29 10:15:06 -08:00
sound ALSA: hda/realtek: Fix mic issue on Acer AIO Veriton Z4860G/Z6860G 2018-12-05 16:39:59 +01:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-09 15:12:33 -08:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt Revert "mm, mmu_notifier: annotate mmu notifiers with blockable invalidate callbacks" 2018-10-26 16:25:19 -07:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.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: change Sparse's maintainer 2018-11-25 09:17:43 -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 2018-12-09 15:12:33 -08:00
Makefile Linux 4.20-rc6 2018-12-09 15:31:00 -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.