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Daniel Vetter f920e413ff mm: track mmu notifiers in fs_reclaim_acquire/release 
fs_reclaim_acquire/release nicely catch recursion issues when allocating
GFP_KERNEL memory against shrinkers (which gpu drivers tend to use to keep
the excessive caches in check).  For mmu notifier recursions we do have
lockdep annotations since 23b68395c7 ("mm/mmu_notifiers: add a lockdep
map for invalidate_range_start/end").

But these only fire if a path actually results in some pte invalidation -
for most small allocations that's very rarely the case.  The other trouble
is that pte invalidation can happen any time when __GFP_RECLAIM is set.
Which means only really GFP_ATOMIC is a safe choice, GFP_NOIO isn't good
enough to avoid potential mmu notifier recursion.

I was pondering whether we should just do the general annotation, but
there's always the risk for false positives.  Plus I'm assuming that the
core fs and io code is a lot better reviewed and tested than random mmu
notifier code in drivers.  Hence why I decide to only annotate for that
specific case.

Furthermore even if we'd create a lockdep map for direct reclaim, we'd
still need to explicit pull in the mmu notifier map - there's a lot more
places that do pte invalidation than just direct reclaim, these two
contexts arent the same.

Note that the mmu notifiers needing their own independent lockdep map is
also the reason we can't hold them from fs_reclaim_acquire to
fs_reclaim_release - it would nest with the acquistion in the pte
invalidation code, causing a lockdep splat.  And we can't remove the
annotations from pte invalidation and all the other places since they're
called from many other places than page reclaim.  Hence we can only do the
equivalent of might_lock, but on the raw lockdep map.

With this we can also remove the lockdep priming added in 66204f1d2d
("mm/mmu_notifiers: prime lockdep") since the new annotations are strictly
more powerful.

Link: https://lkml.kernel.org/r/20201125162532.1299794-2-daniel.vetter@ffwll.ch
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Thomas Hellström (Intel) <thomas_os@shipmail.org>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-15 12:13:41 -08:00
arch mm: forbid splitting special mappings 2020-12-15 12:13:41 -08:00
block block-5.10-2020-12-05 2020-12-05 14:45:30 -08:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto drivers-5.10-2020-10-12 2020-10-13 13:04:41 -07:00
Documentation mm: memcontrol: account pagetables per node 2020-12-15 12:13:40 -08:00
drivers vm_ops: rename .split() callback to .may_split() 2020-12-15 12:13:41 -08:00
fs mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio 2020-12-15 12:13:41 -08:00
include vm_ops: rename .split() callback to .may_split() 2020-12-15 12:13:41 -08:00
init mm: fix page_owner initializing issue for arm32 2020-12-15 12:13:38 -08:00
ipc vm_ops: rename .split() callback to .may_split() 2020-12-15 12:13:41 -08:00
kernel mm: cleanup: remove unused tsk arg from __access_remote_vm 2020-12-15 12:13:40 -08:00
lib selftest/fpu: avoid clang warning 2020-12-11 14:02:14 -08:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm: track mmu notifiers in fs_reclaim_acquire/release 2020-12-15 12:13:41 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2020-12-10 14:29:30 -08:00
samples Tracing fixes for 5.10-rc6 2020-12-01 15:30:18 -08:00
scripts Kbuild fixes for v5.10 (2nd) 2020-12-06 10:31:39 -08:00
security selinux/stable-5.10 PR 20201113 2020-11-14 12:04:02 -08:00
sound ALSA: pcm: use krealloc_array() 2020-12-15 12:13:37 -08:00
tools kselftests: vm: add mremap tests 2020-12-15 12:13:40 -08:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.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: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile Linux 5.10 2020-12-13 14:41:30 -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.