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The list_head counterpart of list_for_each_entry_reverse() was missing,
add it to complete the list handling APIs in <linux/list.h>.
[ This new API is also relied on by a WIP scheduler patch, so this
variant is not a theoretical possibility only. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
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Numerous production kernel configs (see [1, 2]) are choosing to enable
CONFIG_DEBUG_LIST, which is also being recommended by KSPP for hardened
configs [3]. The motivation behind this is that the option can be used
as a security hardening feature (e.g. CVE-2019-2215 and CVE-2019-2025
are mitigated by the option [4]).
The feature has never been designed with performance in mind, yet common
list manipulation is happening across hot paths all over the kernel.
Introduce CONFIG_LIST_HARDENED, which performs list pointer checking
inline, and only upon list corruption calls the reporting slow path.
To generate optimal machine code with CONFIG_LIST_HARDENED:
1. Elide checking for pointer values which upon dereference would
result in an immediate access fault (i.e. minimal hardening
checks). The trade-off is lower-quality error reports.
2. Use the __preserve_most function attribute (available with Clang,
but not yet with GCC) to minimize the code footprint for calling
the reporting slow path. As a result, function size of callers is
reduced by avoiding saving registers before calling the rarely
called reporting slow path.
Note that all TUs in lib/Makefile already disable function tracing,
including list_debug.c, and __preserve_most's implied notrace has
no effect in this case.
3. Because the inline checks are a subset of the full set of checks in
__list_*_valid_or_report(), always return false if the inline
checks failed. This avoids redundant compare and conditional
branch right after return from the slow path.
As a side-effect of the checks being inline, if the compiler can prove
some condition to always be true, it can completely elide some checks.
Since DEBUG_LIST is functionally a superset of LIST_HARDENED, the
Kconfig variables are changed to reflect that: DEBUG_LIST selects
LIST_HARDENED, whereas LIST_HARDENED itself has no dependency on
DEBUG_LIST.
Running netperf with CONFIG_LIST_HARDENED (using a Clang compiler with
"preserve_most") shows throughput improvements, in my case of ~7% on
average (up to 20-30% on some test cases).
Link: https://r.android.com/1266735 [1]
Link: https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/blob/main/config [2]
Link: https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings [3]
Link: https://googleprojectzero.blogspot.com/2019/11/bad-binder-android-in-wild-exploit.html [4]
Signed-off-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20230811151847.1594958-3-elver@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>
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Turn the list debug checking functions __list_*_valid() into inline
functions that wrap the out-of-line functions. Care is taken to ensure
the inline wrappers are always inlined, so that additional compiler
instrumentation (such as sanitizers) does not result in redundant
outlining.
This change is preparation for performing checks in the inline wrappers.
No functional change intended.
Signed-off-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20230811151847.1594958-2-elver@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>
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Some of the existing users, and definitely will be new ones, want to
count existing nodes in the list. Provide a generic API for that by
moving code from i915 to list.h.
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221130134838.23805-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc updates from Andrew Morton:
"The non-MM patch queue for this merge window.
Not a lot of material this cycle. Many singleton patches against
various subsystems. Most notably some maintenance work in ocfs2
and initramfs"
* tag 'mm-nonmm-stable-2022-05-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (65 commits)
kcov: update pos before writing pc in trace function
ocfs2: dlmfs: fix error handling of user_dlm_destroy_lock
ocfs2: dlmfs: don't clear USER_LOCK_ATTACHED when destroying lock
fs/ntfs: remove redundant variable idx
fat: remove time truncations in vfat_create/vfat_mkdir
fat: report creation time in statx
fat: ignore ctime updates, and keep ctime identical to mtime in memory
fat: split fat_truncate_time() into separate functions
MAINTAINERS: add Muchun as a memcg reviewer
proc/sysctl: make protected_* world readable
ia64: mca: drop redundant spinlock initialization
tty: fix deadlock caused by calling printk() under tty_port->lock
relay: remove redundant assignment to pointer buf
fs/ntfs3: validate BOOT sectors_per_clusters
lib/string_helpers: fix not adding strarray to device's resource list
kernel/crash_core.c: remove redundant check of ck_cmdline
ELF, uapi: fixup ELF_ST_TYPE definition
ipc/mqueue: use get_tree_nodev() in mqueue_get_tree()
ipc: update semtimedop() to use hrtimer
ipc/sem: remove redundant assignments
...
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There's a locking issue with the per-netns list of calls in rxrpc. The
pieces of code that add and remove a call from the list use write_lock()
and the calls procfile uses read_lock() to access it. However, the timer
callback function may trigger a removal by trying to queue a call for
processing and finding that it's already queued - at which point it has a
spare refcount that it has to do something with. Unfortunately, if it puts
the call and this reduces the refcount to 0, the call will be removed from
the list. Unfortunately, since the _bh variants of the locking functions
aren't used, this can deadlock.
================================
WARNING: inconsistent lock state
5.18.0-rc3-build4+ #10 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
ksoftirqd/2/25 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff888107ac4038 (&rxnet->call_lock){+.?.}-{2:2}, at: rxrpc_put_call+0x103/0x14b
{SOFTIRQ-ON-W} state was registered at:
...
Possible unsafe locking scenario:
CPU0
----
lock(&rxnet->call_lock);
<Interrupt>
lock(&rxnet->call_lock);
*** DEADLOCK ***
1 lock held by ksoftirqd/2/25:
#0: ffff8881008ffdb0 ((&call->timer)){+.-.}-{0:0}, at: call_timer_fn+0x5/0x23d
Changes
=======
ver #2)
- Changed to using list_next_rcu() rather than rcu_dereference() directly.
Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: David S. Miller <davem@davemloft.net>
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Add macros to get the next or previous entries and wraparound if
needed. For example, calling list_next_entry_circular() on the last
element should return the first element in the list.
Signed-off-by: Ricardo Martinez <ricardo.martinez@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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ep_poll() first calls ep_events_available() with no lock held and checks
if ep->rdllist is empty by list_empty_careful(), which reads
rdllist->prev. Thus all accesses to it need some protection to avoid
store/load-tearing.
Note INIT_LIST_HEAD_RCU() already has the annotation for both prev
and next.
Commit bf3b9f6372c4 ("epoll: Add busy poll support to epoll with socket
fds.") added the first lockless ep_events_available(), and commit
c5a282e9635e ("fs/epoll: reduce the scope of wq lock in epoll_wait()")
made some ep_events_available() calls lockless and added single call under
a lock, finally commit e59d3c64cba6 ("epoll: eliminate unnecessary lock
for zero timeout") made the last ep_events_available() lockless.
BUG: KCSAN: data-race in do_epoll_wait / do_epoll_wait
write to 0xffff88810480c7d8 of 8 bytes by task 1802 on cpu 0:
INIT_LIST_HEAD include/linux/list.h:38 [inline]
list_splice_init include/linux/list.h:492 [inline]
ep_start_scan fs/eventpoll.c:622 [inline]
ep_send_events fs/eventpoll.c:1656 [inline]
ep_poll fs/eventpoll.c:1806 [inline]
do_epoll_wait+0x4eb/0xf40 fs/eventpoll.c:2234
do_epoll_pwait fs/eventpoll.c:2268 [inline]
__do_sys_epoll_pwait fs/eventpoll.c:2281 [inline]
__se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2275
__x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2275
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
read to 0xffff88810480c7d8 of 8 bytes by task 1799 on cpu 1:
list_empty_careful include/linux/list.h:329 [inline]
ep_events_available fs/eventpoll.c:381 [inline]
ep_poll fs/eventpoll.c:1797 [inline]
do_epoll_wait+0x279/0xf40 fs/eventpoll.c:2234
do_epoll_pwait fs/eventpoll.c:2268 [inline]
__do_sys_epoll_pwait fs/eventpoll.c:2281 [inline]
__se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2275
__x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2275
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
value changed: 0xffff88810480c7d0 -> 0xffff888103c15098
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1799 Comm: syz-fuzzer Tainted: G W 5.17.0-rc7-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Link: https://lkml.kernel.org/r/20220322002653.33865-3-kuniyu@amazon.co.jp
Fixes: e59d3c64cba6 ("epoll: eliminate unnecessary lock for zero timeout")
Fixes: c5a282e9635e ("fs/epoll: reduce the scope of wq lock in epoll_wait()")
Fixes: bf3b9f6372c4 ("epoll: Add busy poll support to epoll with socket fds.")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Reported-by: syzbot+bdd6e38a1ed5ee58d8bd@syzkaller.appspotmail.com
Cc: Al Viro <viro@zeniv.linux.org.uk>, Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Cc: Kuniyuki Iwashima <kuni1840@gmail.com>
Cc: "Soheil Hassas Yeganeh" <soheil@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Sridhar Samudrala" <sridhar.samudrala@intel.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Introduce list_is_head() in the similar (*) way as it's done for
list_entry_is_head(). Make use of it in the list.h.
*) it's done as inliner and not a macro to be aligned with other
list_is_*() APIs; while at it, make all three to have the same
style.
Link: https://lkml.kernel.org/r/20211201141824.81400-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When kernel.h is used in the headers it adds a lot into dependency hell,
especially when there are circular dependencies are involved.
Replace kernel.h inclusion with the list of what is really being used.
Link: https://lkml.kernel.org/r/20211013170417.87909-5-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
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>
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hlist_add_behing -> hlist_add_behind
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The students in the Operating System Lecture Section at the
American University of Sharjah were confused by the header comment
in include/linux/list.h, which says "Simple doubly linked list
implementation". This comment means "simple" as in "not complex",
but "simple" is often used in this context to mean "not circular".
This commit therefore avoids this ambiguity by explicitly calling out
"circular".
Signed-off-by: Asif Rasheed <b00073877@aus.edu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Add a macro to test if entry is pointing to the head of the list which is
useful in cases like:
list_for_each_entry(pos, &head, member) {
if (cond)
break;
}
if (list_entry_is_head(pos, &head, member))
return -ERRNO;
that allows to avoid additional variable to be added to track if loop has
not been stopped in the middle.
While here, convert list_for_each_entry*() family of macros to use a new one.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lkml.kernel.org/r/20200929134342.51489-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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That gives us ordering guarantees around the pair.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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hash_for_each_safe() and hash_for_each_possible_safe()
need to be passed a temp 'struct hlist_node' pointer, but
do not say that in the documentation - they just say
a 'struct'.
Also the documentation for hlist_for_each_entry_safe()
describes @n as "another" hlist_node, but in reality it is
the only one.
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"The RCU changes in this cycle were:
- Expedited grace-period updates
- kfree_rcu() updates
- RCU list updates
- Preemptible RCU updates
- Torture-test updates
- Miscellaneous fixes
- Documentation updates"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (69 commits)
rcu: Remove unused stop-machine #include
powerpc: Remove comment about read_barrier_depends()
.mailmap: Add entries for old paulmck@kernel.org addresses
srcu: Apply *_ONCE() to ->srcu_last_gp_end
rcu: Switch force_qs_rnp() to for_each_leaf_node_cpu_mask()
rcu: Move rcu_{expedited,normal} definitions into rcupdate.h
rcu: Move gp_state_names[] and gp_state_getname() to tree_stall.h
rcu: Remove the declaration of call_rcu() in tree.h
rcu: Fix tracepoint tracking RCU CPU kthread utilization
rcu: Fix harmless omission of "CONFIG_" from #if condition
rcu: Avoid tick_dep_set_cpu() misordering
rcu: Provide wrappers for uses of ->rcu_read_lock_nesting
rcu: Use READ_ONCE() for ->expmask in rcu_read_unlock_special()
rcu: Clear ->rcu_read_unlock_special only once
rcu: Clear .exp_hint only when deferred quiescent state has been reported
rcu: Rename some instance of CONFIG_PREEMPTION to CONFIG_PREEMPT_RCU
rcu: Remove kfree_call_rcu_nobatch()
rcu: Remove kfree_rcu() special casing and lazy-callback handling
rcu: Add support for debug_objects debugging for kfree_rcu()
rcu: Add multiple in-flight batches of kfree_rcu() work
...
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[ paulmck: Fix typo found by kbuild test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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As other *continue() helpers, this continues iteration from a given
position.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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We would like to use hlist_unhashed() from timer_pending(),
which runs without protection of a lock.
Note that other callers might also want to use this variant.
Instead of forcing a READ_ONCE() for all hlist_unhashed()
callers, add a new helper with an explicit _lockless suffix
in the name to better document what is going on.
Also add various WRITE_ONCE() in __hlist_del(), hlist_add_head()
and hlist_add_before()/hlist_add_behind() to pair with
the READ_ONCE().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
[ paulmck: Also add WRITE_ONCE() to rculist.h. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Add a helper in list.h for the non-standard way of clearing a list that is
used in xskmap. This makes it easier to reuse it in the other map types,
and also makes sure this usage is not forgotten in any list refactorings in
the future.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- Improve DM snapshot target's scalability by using finer grained
locking. Requires some list_bl interface improvements.
- Add ability for DM integrity to use a bitmap mode, that tracks
regions where data and metadata are out of sync, instead of using a
journal.
- Improve DM thin provisioning target to not write metadata changes to
disk if the thin-pool and associated thin devices are merely
activated but not used. This avoids metadata corruption due to
concurrent activation of thin devices across different OS instances
(e.g. split brain scenarios, which ultimately would be avoided if
proper device filters were used -- but not having proper filtering
has proven a very common configuration mistake)
- Fix missing call to path selector type->end_io in DM multipath. This
fixes reported performance problems due to inaccurate path selector
IO accounting causing an imbalance of IO (e.g. avoiding issuing IO to
particular path due to it seemingly being heavily used).
- Fix bug in DM cache metadata's loading of its discard bitset that
could lead to all cache blocks being discarded if the very first
cache block was discarded (thankfully in practice the first cache
block is generally in use; be it FS superblock, partition table, disk
label, etc).
- Add testing-only DM dust target which simulates a device that has
failing sectors and/or read failures.
- Fix a DM init error path reference count hang that caused boot hangs
if user supplied malformed input on kernel commandline.
- Fix a couple issues with DM crypt target's logging being overly
verbose or lacking context.
- Various other small fixes to DM init, DM multipath, DM zoned, and DM
crypt.
* tag 'for-5.2/dm-changes-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (42 commits)
dm: fix a couple brace coding style issues
dm crypt: print device name in integrity error message
dm crypt: move detailed message into debug level
dm ioctl: fix hang in early create error condition
dm integrity: whitespace, coding style and dead code cleanup
dm integrity: implement synchronous mode for reboot handling
dm integrity: handle machine reboot in bitmap mode
dm integrity: add a bitmap mode
dm integrity: introduce a function add_new_range_and_wait()
dm integrity: allow large ranges to be described
dm ingerity: pass size to dm_integrity_alloc_page_list()
dm integrity: introduce rw_journal_sectors()
dm integrity: update documentation
dm integrity: don't report unused options
dm integrity: don't check null pointer before kvfree and vfree
dm integrity: correctly calculate the size of metadata area
dm dust: Make dm_dust_init and dm_dust_exit static
dm dust: remove redundant unsigned comparison to less than zero
dm mpath: always free attached_handler_name in parse_path()
dm init: fix max devices/targets checks
...
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Patch series "mm: Randomize free memory", v10.
This patch (of 3):
Randomization of the page allocator improves the average utilization of
a direct-mapped memory-side-cache. Memory side caching is a platform
capability that Linux has been previously exposed to in HPC
(high-performance computing) environments on specialty platforms. In
that instance it was a smaller pool of high-bandwidth-memory relative to
higher-capacity / lower-bandwidth DRAM. Now, this capability is going
to be found on general purpose server platforms where DRAM is a cache in
front of higher latency persistent memory [1].
Robert offered an explanation of the state of the art of Linux
interactions with memory-side-caches [2], and I copy it here:
It's been a problem in the HPC space:
http://www.nersc.gov/research-and-development/knl-cache-mode-performance-coe/
A kernel module called zonesort is available to try to help:
https://software.intel.com/en-us/articles/xeon-phi-software
and this abandoned patch series proposed that for the kernel:
https://lkml.kernel.org/r/20170823100205.17311-1-lukasz.daniluk@intel.com
Dan's patch series doesn't attempt to ensure buffers won't conflict, but
also reduces the chance that the buffers will. This will make performance
more consistent, albeit slower than "optimal" (which is near impossible
to attain in a general-purpose kernel). That's better than forcing
users to deploy remedies like:
"To eliminate this gradual degradation, we have added a Stream
measurement to the Node Health Check that follows each job;
nodes are rebooted whenever their measured memory bandwidth
falls below 300 GB/s."
A replacement for zonesort was merged upstream in commit cc9aec03e58f
("x86/numa_emulation: Introduce uniform split capability"). With this
numa_emulation capability, memory can be split into cache sized
("near-memory" sized) numa nodes. A bind operation to such a node, and
disabling workloads on other nodes, enables full cache performance.
However, once the workload exceeds the cache size then cache conflicts
are unavoidable. While HPC environments might be able to tolerate
time-scheduling of cache sized workloads, for general purpose server
platforms, the oversubscribed cache case will be the common case.
The worst case scenario is that a server system owner benchmarks a
workload at boot with an un-contended cache only to see that performance
degrade over time, even below the average cache performance due to
excessive conflicts. Randomization clips the peaks and fills in the
valleys of cache utilization to yield steady average performance.
Here are some performance impact details of the patches:
1/ An Intel internal synthetic memory bandwidth measurement tool, saw a
3X speedup in a contrived case that tries to force cache conflicts.
The contrived cased used the numa_emulation capability to force an
instance of the benchmark to be run in two of the near-memory sized
numa nodes. If both instances were placed on the same emulated they
would fit and cause zero conflicts. While on separate emulated nodes
without randomization they underutilized the cache and conflicted
unnecessarily due to the in-order allocation per node.
2/ A well known Java server application benchmark was run with a heap
size that exceeded cache size by 3X. The cache conflict rate was 8%
for the first run and degraded to 21% after page allocator aging. With
randomization enabled the rate levelled out at 11%.
3/ A MongoDB workload did not observe measurable difference in
cache-conflict rates, but the overall throughput dropped by 7% with
randomization in one case.
4/ Mel Gorman ran his suite of performance workloads with randomization
enabled on platforms without a memory-side-cache and saw a mix of some
improvements and some losses [3].
While there is potentially significant improvement for applications that
depend on low latency access across a wide working-set, the performance
may be negligible to negative for other workloads. For this reason the
shuffle capability defaults to off unless a direct-mapped
memory-side-cache is detected. Even then, the page_alloc.shuffle=0
parameter can be specified to disable the randomization on those systems.
Outside of memory-side-cache utilization concerns there is potentially
security benefit from randomization. Some data exfiltration and
return-oriented-programming attacks rely on the ability to infer the
location of sensitive data objects. The kernel page allocator, especially
early in system boot, has predictable first-in-first out behavior for
physical pages. Pages are freed in physical address order when first
onlined.
Quoting Kees:
"While we already have a base-address randomization
(CONFIG_RANDOMIZE_MEMORY), attacks against the same hardware and
memory layouts would certainly be using the predictability of
allocation ordering (i.e. for attacks where the base address isn't
important: only the relative positions between allocated memory).
This is common in lots of heap-style attacks. They try to gain
control over ordering by spraying allocations, etc.
I'd really like to see this because it gives us something similar
to CONFIG_SLAB_FREELIST_RANDOM but for the page allocator."
While SLAB_FREELIST_RANDOM reduces the predictability of some local slab
caches it leaves vast bulk of memory to be predictably in order allocated.
However, it should be noted, the concrete security benefits are hard to
quantify, and no known CVE is mitigated by this randomization.
Introduce shuffle_free_memory(), and its helper shuffle_zone(), to perform
a Fisher-Yates shuffle of the page allocator 'free_area' lists when they
are initially populated with free memory at boot and at hotplug time. Do
this based on either the presence of a page_alloc.shuffle=Y command line
parameter, or autodetection of a memory-side-cache (to be added in a
follow-on patch).
The shuffling is done in terms of CONFIG_SHUFFLE_PAGE_ORDER sized free
pages where the default CONFIG_SHUFFLE_PAGE_ORDER is MAX_ORDER-1 i.e. 10,
4MB this trades off randomization granularity for time spent shuffling.
MAX_ORDER-1 was chosen to be minimally invasive to the page allocator
while still showing memory-side cache behavior improvements, and the
expectation that the security implications of finer granularity
randomization is mitigated by CONFIG_SLAB_FREELIST_RANDOM. The
performance impact of the shuffling appears to be in the noise compared to
other memory initialization work.
This initial randomization can be undone over time so a follow-on patch is
introduced to inject entropy on page free decisions. It is reasonable to
ask if the page free entropy is sufficient, but it is not enough due to
the in-order initial freeing of pages. At the start of that process
putting page1 in front or behind page0 still keeps them close together,
page2 is still near page1 and has a high chance of being adjacent. As
more pages are added ordering diversity improves, but there is still high
page locality for the low address pages and this leads to no significant
impact to the cache conflict rate.
[1]: https://itpeernetwork.intel.com/intel-optane-dc-persistent-memory-operating-modes/
[2]: https://lkml.kernel.org/r/AT5PR8401MB1169D656C8B5E121752FC0F8AB120@AT5PR8401MB1169.NAMPRD84.PROD.OUTLOOK.COM
[3]: https://lkml.org/lkml/2018/10/12/309
[dan.j.williams@intel.com: fix shuffle enable]
Link: http://lkml.kernel.org/r/154943713038.3858443.4125180191382062871.stgit@dwillia2-desk3.amr.corp.intel.com
[cai@lca.pw: fix SHUFFLE_PAGE_ALLOCATOR help texts]
Link: http://lkml.kernel.org/r/20190425201300.75650-1-cai@lca.pw
Link: http://lkml.kernel.org/r/154899811738.3165233.12325692939590944259.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Robert Elliott <elliott@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "mm: Use slab_list list_head instead of lru", v5.
Currently the slab allocators (ab)use the struct page 'lru' list_head. We
have a list head for slab allocators to use, 'slab_list'.
During v2 it was noted by Christoph that the SLOB allocator was reaching
into a list_head, this version adds 2 patches to the front of the set to
fix that.
Clean up all three allocators by using the 'slab_list' list_head instead
of overloading the 'lru' list_head.
This patch (of 7):
Currently if we wish to rotate a list until a specific item is at the
front of the list we can call list_move_tail(head, list). Note that the
arguments are the reverse way to the usual use of list_move_tail(list,
head). This is a hack, it depends on the developer knowing how the
list_head operates internally which violates the layer of abstraction
offered by the list_head. Also, it is not intuitive so the next developer
to come along must study list.h in order to fully understand what is meant
by the call, while this is 'good for' the developer it makes reading the
code harder. We should have an function appropriately named that does
this if there are users for it intree.
By grep'ing the tree for list_move_tail() and list_tail() and attempting
to guess the argument order from the names it seems there is only one
place currently in the tree that does this - the slob allocatator.
Add function list_rotate_to_front() to rotate a list until the specified
item is at the front of the list.
Link: http://lkml.kernel.org/r/20190402230545.2929-2-tobin@kernel.org
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Commit 1c97be677f72b3 ("list: Use WRITE_ONCE() when adding to lists and
hlists") introduced the use of WRITE_ONCE() to atomically write the list
head's ->next pointer.
hlist_add_behind() doesn't touch the hlist head's ->first pointer so
there is no reason to use WRITE_ONCE() in this case.
Co-developed-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
|
|
Fix typo of kernel-doc parameter notation (there should be no space
between '@' and the parameter name).
Also fixes bogus kernel-doc notation output formatting.
Link: http://lkml.kernel.org/r/ddce8b80-9a8a-d52d-3546-87b2211c089a@infradead.org
Fixes: 70b44595eafe9 ("mm, compaction: use free lists to quickly locate a migration source")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The migration scanner is a linear scan of a zone with a potentiall large
search space. Furthermore, many pageblocks are unusable such as those
filled with reserved pages or partially filled with pages that cannot
migrate. These still get scanned in the common case of allocating a THP
and the cost accumulates.
The patch uses a partial search of the free lists to locate a migration
source candidate that is marked as MOVABLE when allocating a THP. It
prefers picking a block with a larger number of free pages already on
the basis that there are fewer pages to migrate to free the entire
block. The lowest PFN found during searches is tracked as the basis of
the start for the linear search after the first search of the free list
fails. After the search, the free list is shuffled so that the next
search will not encounter the same page. If the search fails then the
subsequent searches will be shorter and the linear scanner is used.
If this search fails, or if the request is for a small or
unmovable/reclaimable allocation then the linear scanner is still used.
It is somewhat pointless to use the list search in those cases. Small
free pages must be used for the search and there is no guarantee that
movable pages are located within that block that are contiguous.
5.0.0-rc1 5.0.0-rc1
noboost-v3r10 findmig-v3r15
Amean fault-both-3 3771.41 ( 0.00%) 3390.40 ( 10.10%)
Amean fault-both-5 5409.05 ( 0.00%) 5082.28 ( 6.04%)
Amean fault-both-7 7040.74 ( 0.00%) 7012.51 ( 0.40%)
Amean fault-both-12 11887.35 ( 0.00%) 11346.63 ( 4.55%)
Amean fault-both-18 16718.19 ( 0.00%) 15324.19 ( 8.34%)
Amean fault-both-24 21157.19 ( 0.00%) 16088.50 * 23.96%*
Amean fault-both-30 21175.92 ( 0.00%) 18723.42 * 11.58%*
Amean fault-both-32 21339.03 ( 0.00%) 18612.01 * 12.78%*
5.0.0-rc1 5.0.0-rc1
noboost-v3r10 findmig-v3r15
Percentage huge-3 86.50 ( 0.00%) 89.83 ( 3.85%)
Percentage huge-5 92.52 ( 0.00%) 91.96 ( -0.61%)
Percentage huge-7 92.44 ( 0.00%) 92.85 ( 0.44%)
Percentage huge-12 92.98 ( 0.00%) 92.74 ( -0.25%)
Percentage huge-18 91.70 ( 0.00%) 91.71 ( 0.02%)
Percentage huge-24 91.59 ( 0.00%) 92.13 ( 0.60%)
Percentage huge-30 90.14 ( 0.00%) 93.79 ( 4.04%)
Percentage huge-32 90.03 ( 0.00%) 91.27 ( 1.37%)
This shows an improvement in allocation latencies with similar
allocation success rates. While not presented, there was a 31%
reduction in migration scanning and a 8% reduction on system CPU usage.
A 2-socket machine showed similar benefits.
[mgorman@techsingularity.net: several fixes]
Link: http://lkml.kernel.org/r/20190204120111.GL9565@techsingularity.net
[vbabka@suse.cz: migrate block that was found-fast, some optimisations]
Link: http://lkml.kernel.org/r/20190118175136.31341-10-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <Vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Move all entries between @first and including @last before @head.
This is useful for LRU lists where a whole block of entries should be
moved to the end of the list.
Used as a band aid in TTM, but better placed in the common list headers.
Acked-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
|
|
First example of a layer splitting the list (rather than merely taking
individual packets off it).
Involves new list.h function, list_cut_before(), like list_cut_position()
but cuts on the other side of the given entry.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
|
|
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
Similar to list_for_each_entry_continue and its reverse variant
list_for_each_entry_continue_reverse, introduce reverse helper for
list_for_each_entry_from.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
|
|
Similar to the list_add() debug consolidation, this commit consolidates
the debug checking performed during CONFIG_DEBUG_LIST into a new
__list_del_entry_valid() function, and stops list updates when corruption
is found.
Refactored from same hardening in PaX and Grsecurity.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Rik van Riel <riel@redhat.com>
|
|
Right now, __list_add() code is repeated either in list.h or in
list_debug.c, but the only differences between the two versions
are the debug checks. This commit therefore extracts these debug
checks into a separate __list_add_valid() function and consolidates
__list_add(). Additionally this new __list_add_valid() function will stop
list manipulations if a corruption is detected, instead of allowing for
further corruption that may lead to even worse conditions.
This is slight refactoring of the same hardening done in PaX and Grsecurity.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Rik van Riel <riel@redhat.com>
|
|
Due to the use of READ_ONCE() in list_empty() the compiler cannot
optimise !list_empty() ? list_first_entry() : NULL very well. By
manually expanding list_first_entry_or_null() we can take advantage of
the READ_ONCE() to avoid the list element changing under the test while
the compiler can generate smaller code.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Josef Bacik <jbacik@fb.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
|
|
Required to figure out whether the entry is the only one in the hlist.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.867631372@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Given we have uninitialized list_heads being passed to list_add() it
will always be the case that those uninitialized values randomly trigger
the poison value. Especially since a list_add() operation will seed the
stack with the poison value for later stack allocations to trip over.
For example, see these two false positive reports:
list_add attempted on force-poisoned entry
WARNING: at lib/list_debug.c:34
[..]
NIP [c00000000043c390] __list_add+0xb0/0x150
LR [c00000000043c38c] __list_add+0xac/0x150
Call Trace:
__list_add+0xac/0x150 (unreliable)
__down+0x4c/0xf8
down+0x68/0x70
xfs_buf_lock+0x4c/0x150 [xfs]
list_add attempted on force-poisoned entry(0000000000000500),
new->next == d0000000059ecdb0, new->prev == 0000000000000500
WARNING: at lib/list_debug.c:33
[..]
NIP [c00000000042db78] __list_add+0xa8/0x140
LR [c00000000042db74] __list_add+0xa4/0x140
Call Trace:
__list_add+0xa4/0x140 (unreliable)
rwsem_down_read_failed+0x6c/0x1a0
down_read+0x58/0x60
xfs_log_commit_cil+0x7c/0x600 [xfs]
Fixes: commit 5c2c2587b132 ("mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Eryu Guan <eguan@redhat.com>
Tested-by: Eryu Guan <eguan@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
get_dev_page() enables paths like get_user_pages() to pin a dynamically
mapped pfn-range (devm_memremap_pages()) while the resulting struct page
objects are in use. Unlike get_page() it may fail if the device is, or
is in the process of being, disabled. While the initial lookup of the
range may be an expensive list walk, the result is cached to speed up
subsequent lookups which are likely to be in the same mapped range.
devm_memremap_pages() now requires a reference counter to be specified
at init time. For pmem this means moving request_queue allocation into
pmem_alloc() so the existing queue usage counter can track "device
pages".
ZONE_DEVICE pages always have an elevated count and will never be on an
lru reclaim list. That space in 'struct page' can be redirected for
other uses, but for safety introduce a poison value that will always
trip __list_add() to assert. This allows half of the struct list_head
storage to be reclaimed with some assurance to back up the assumption
that the page count never goes to zero and a list_add() is never
attempted.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Code that does lockless emptiness testing of non-RCU lists is relying
on INIT_LIST_HEAD() to write the list head's ->next pointer atomically,
particularly when INIT_LIST_HEAD() is invoked from list_del_init().
This commit therefore adds WRITE_ONCE() to this function's pointer stores
that could affect the head's ->next pointer.
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
|
|
Most of the list-empty-check macros (list_empty(), hlist_empty(),
hlist_bl_empty(), hlist_nulls_empty(), and hlist_nulls_empty()) use
an unadorned load to check the list header. Given that these macros
are sometimes invoked without the protection of a lock, this is
not sufficient. This commit therefore adds READ_ONCE() calls to
them. This commit does not touch llist_empty() because it already
has the needed ACCESS_ONCE().
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
|
|
Code that does lockless emptiness testing of non-RCU lists is relying
on the list-addition code to write the list head's ->next pointer
atomically. This commit therefore adds WRITE_ONCE() to list-addition
pointer stores that could affect the head's ->next pointer.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
|
|
The various RCU list-deletion macros (list_del_rcu(),
hlist_del_init_rcu(), hlist_del_rcu(), hlist_bl_del_init_rcu(),
hlist_bl_del_rcu(), hlist_nulls_del_init_rcu(), and hlist_nulls_del_rcu())
do plain stores into the ->next pointer of the preceding list elemment.
Unfortunately, the compiler is within its rights to (for example) use
byte-at-a-time writes to update the pointer, which would fatally confuse
concurrent readers. This patch therefore adds the needed WRITE_ONCE()
macros.
KernelThreadSanitizer (KTSAN) reported the __hlist_del() issue, which
is a problem when __hlist_del() is invoked by hlist_del_rcu().
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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Some filesystems don't use the VFS inode hash and fake the fact they
are hashed so that all the writeback code works correctly. However,
this means the evict() path still tries to remove the inode from the
hash, meaning that the inode_hash_lock() needs to be taken
unnecessarily. Hence under certain workloads the inode_hash_lock can
be contended even if the inode is never actually hashed.
To avoid this add hlist_fake to test if the inode isn't actually
hashed to avoid taking the hash lock on inodes that have never been
hashed. Based on Dave Chinner's
inode: add IOP_NOTHASHED to avoid inode hash lock in evict
basd on Al's suggestions. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Dave Chinner <dchinner@redhat.com>
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There's no such thing as "list_struct".
Signed-off-by: Andrey Utkin <andrey.krieger.utkin@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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linux/list.h uses container_of, therefore it depends on linux/kernel.h.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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All other add functions for lists have the new item as first argument
and the position where it is added as second argument. This was changed
for no good reason in this function and makes using it unnecessary
confusing.
The name was changed to hlist_add_behind() to cause unconverted code to
generate a compile error instead of using the wrong parameter order.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Ken Helias <kenhelias@firemail.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> [intel driver bits]
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The argument names for hlist_add_after() are poorly chosen because they
look the same as the ones for hlist_add_before() but have to be used
differently.
hlist_add_after_rcu() has made a better choice.
Signed-off-by: Ken Helias <kenhelias@firemail.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We already have list_first_entry(), it makes sense to also add
list_last_entry() for consistency. And we use both helpers in
list_for_each_*().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Now that we have list_{next,prev}_entry() we can change
list_for_each_entry*() and list_safe_reset_next() to use the new helpers
to improve the readability.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add two trivial helpers list_next_entry() and list_prev_entry(), they
can have a lot of users including list.h itself. In fact the 1st one is
already defined in events/core.c and bnx2x_sp.c, so the patch simply
moves the definition to list.h.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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__list_for_each used to be the non prefetch() aware list walking
primitive. When we removed the prefetch macros from the list routines,
it became redundant. Given it does exactly the same thing as
list_for_each now, we might as well remove it and call list_for_each
directly.
All users of __list_for_each have been converted to list_for_each calls
in the current merge window.
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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non-rcu variant of list_first_or_null_rcu
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
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