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__read_mostly predates __ro_after_init. Many variables which are marked
__read_mostly should have been __ro_after_init from day 1.
Also, mark some stuff as "const" and "__init" while I'm at it.
[akpm@linux-foundation.org: revert sysctl_nr_open_min, sysctl_nr_open_max changes due to arm warning]
[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/4f6bb9c0-abba-4ee4-a7aa-89265e886817@p183
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The get_current_user() does not fail, and moving it after kzalloc() can
simplify the code a bit.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Message-Id: <20230726032135.933-1-thunder.leizhen@huaweicloud.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Merge tag 'v6.5/vfs.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"Miscellaneous features, cleanups, and fixes for vfs and individual fs
Features:
- Use mode 0600 for file created by cachefilesd so it can be run by
unprivileged users. This aligns them with directories which are
already created with mode 0700 by cachefilesd
- Reorder a few members in struct file to prevent some false sharing
scenarios
- Indicate that an eventfd is used a semaphore in the eventfd's
fdinfo procfs file
- Add a missing uapi header for eventfd exposing relevant uapi
defines
- Let the VFS protect transitions of a superblock from read-only to
read-write in addition to the protection it already provides for
transitions from read-write to read-only. Protecting read-only to
read-write transitions allows filesystems such as ext4 to perform
internal writes, keeping writers away until the transition is
completed
Cleanups:
- Arnd removed the architecture specific arch_report_meminfo()
prototypes and added a generic one into procfs.h. Note, we got a
report about a warning in amdpgpu codepaths that suggested this was
bisectable to this change but we concluded it was a false positive
- Remove unused parameters from split_fs_names()
- Rename put_and_unmap_page() to unmap_and_put_page() to let the name
reflect the order of the cleanup operation that has to unmap before
the actual put
- Unexport buffer_check_dirty_writeback() as it is not used outside
of block device aops
- Stop allocating aio rings from highmem
- Protecting read-{only,write} transitions in the VFS used open-coded
barriers in various places. Replace them with proper little helpers
and document both the helpers and all barrier interactions involved
when transitioning between read-{only,write} states
- Use flexible array members in old readdir codepaths
Fixes:
- Use the correct type __poll_t for epoll and eventfd
- Replace all deprecated strlcpy() invocations, whose return value
isn't checked with an equivalent strscpy() call
- Fix some kernel-doc warnings in fs/open.c
- Reduce the stack usage in jffs2's xattr codepaths finally getting
rid of this: fs/jffs2/xattr.c:887:1: error: the frame size of 1088
bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
royally annoying compilation warning
- Use __FMODE_NONOTIFY instead of FMODE_NONOTIFY where an int and not
fmode_t is required to avoid fmode_t to integer degradation
warnings
- Create coredumps with O_WRONLY instead of O_RDWR. There's a long
explanation in that commit how O_RDWR is actually a bug which we
found out with the help of Linus and git archeology
- Fix "no previous prototype" warnings in the pipe codepaths
- Add overflow calculations for remap_verify_area() as a signed
addition overflow could be triggered in xfstests
- Fix a null pointer dereference in sysv
- Use an unsigned variable for length calculations in jfs avoiding
compilation warnings with gcc 13
- Fix a dangling pipe pointer in the watch queue codepath
- The legacy mount option parser provided as a fallback by the VFS
for filesystems not yet converted to the new mount api did prefix
the generated mount option string with a leading ',' causing issues
for some filesystems
- Fix a repeated word in a comment in fs.h
- autofs: Update the ctime when mtime is updated as mandated by
POSIX"
* tag 'v6.5/vfs.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (27 commits)
readdir: Replace one-element arrays with flexible-array members
fs: Provide helpers for manipulating sb->s_readonly_remount
fs: Protect reconfiguration of sb read-write from racing writes
eventfd: add a uapi header for eventfd userspace APIs
autofs: set ctime as well when mtime changes on a dir
eventfd: show the EFD_SEMAPHORE flag in fdinfo
fs/aio: Stop allocating aio rings from HIGHMEM
fs: Fix comment typo
fs: unexport buffer_check_dirty_writeback
fs: avoid empty option when generating legacy mount string
watch_queue: prevent dangling pipe pointer
fs.h: Optimize file struct to prevent false sharing
highmem: Rename put_and_unmap_page() to unmap_and_put_page()
cachefiles: Allow the cache to be non-root
init: remove unused names parameter in split_fs_names()
jfs: Use unsigned variable for length calculations
fs/sysv: Null check to prevent null-ptr-deref bug
fs: use UB-safe check for signed addition overflow in remap_verify_area
procfs: consolidate arch_report_meminfo declaration
fs: pipe: reveal missing function protoypes
...
autoremove_wake_function uses list_del_init_careful, so should epoll's
more aggressive variant. It only doesn't because it was copied from an
older wait.c rather than the most recent.
[bsegall@google.com: add comment]
Link: https://lkml.kernel.org/r/xm26bki0ulsr.fsf_-_@google.com
Link: https://lkml.kernel.org/r/xm26pm6hvfer.fsf@google.com
Fixes: a16ceb1396 ("epoll: autoremove wakers even more aggressively")
Signed-off-by: Ben Segall <bsegall@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fix the following sparse warnings by using __poll_t instead
of unsigned type.
fs/eventpoll.c:541:9: sparse: warning: restricted __poll_t degrades to integer
fs/eventfd.c:67:17: sparse: warning: restricted __poll_t degrades to integer
Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Message-Id: <20230511164628.336586-1-minhuadotchen@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
- updates to scripts/gdb from Glenn Washburn
- kexec cleanups from Bjorn Helgaas
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Merge tag 'mm-nonmm-stable-2023-04-27-16-01' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-MM updates from Andrew Morton:
"Mainly singleton patches all over the place.
Series of note are:
- updates to scripts/gdb from Glenn Washburn
- kexec cleanups from Bjorn Helgaas"
* tag 'mm-nonmm-stable-2023-04-27-16-01' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (50 commits)
mailmap: add entries for Paul Mackerras
libgcc: add forward declarations for generic library routines
mailmap: add entry for Oleksandr
ocfs2: reduce ioctl stack usage
fs/proc: add Kthread flag to /proc/$pid/status
ia64: fix an addr to taddr in huge_pte_offset()
checkpatch: introduce proper bindings license check
epoll: rename global epmutex
scripts/gdb: add GDB convenience functions $lx_dentry_name() and $lx_i_dentry()
scripts/gdb: create linux/vfs.py for VFS related GDB helpers
uapi/linux/const.h: prefer ISO-friendly __typeof__
delayacct: track delays from IRQ/SOFTIRQ
scripts/gdb: timerlist: convert int chunks to str
scripts/gdb: print interrupts
scripts/gdb: raise error with reduced debugging information
scripts/gdb: add a Radix Tree Parser
lib/rbtree: use '+' instead of '|' for setting color.
proc/stat: remove arch_idle_time()
checkpatch: check for misuse of the link tags
checkpatch: allow Closes tags with links
...
These are various cleanups, fixing a number of uapi header files to no
longer reference CONFIG_* symbols, and one patch that introduces the
new CONFIG_HAS_IOPORT symbol for architectures that provide working
inb()/outb() macros, as a preparation for adding driver dependencies
on those in the following release.
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Merge tag 'asm-generic-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic
Pull asm-generic updates from Arnd Bergmann:
"These are various cleanups, fixing a number of uapi header files to no
longer reference CONFIG_* symbols, and one patch that introduces the
new CONFIG_HAS_IOPORT symbol for architectures that provide working
inb()/outb() macros, as a preparation for adding driver dependencies
on those in the following release"
* tag 'asm-generic-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
Kconfig: introduce HAS_IOPORT option and select it as necessary
scripts: Update the CONFIG_* ignore list in headers_install.sh
pktcdvd: Remove CONFIG_CDROM_PKTCDVD_WCACHE from uapi header
Move bp_type_idx to include/linux/hw_breakpoint.h
Move ep_take_care_of_epollwakeup() to fs/eventpoll.c
Move COMPAT_ATM_ADDPARTY to net/atm/svc.c
As of 4f04cbaf128 ("epoll: use refcount to reduce ep_mutex contention"),
this lock is now specific to nesting cases - inserting an epoll fd onto
another epoll fd. Rename the lock to be less generic.
Link: https://lkml.kernel.org/r/20230411234159.20421-1-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We are observing huge contention on the epmutex during an http
connection/rate test:
83.17% 0.25% nginx [kernel.kallsyms] [k] entry_SYSCALL_64_after_hwframe
[...]
|--66.96%--__fput
|--60.04%--eventpoll_release_file
|--58.41%--__mutex_lock.isra.6
|--56.56%--osq_lock
The application is multi-threaded, creates a new epoll entry for
each incoming connection, and does not delete it before the
connection shutdown - that is, before the connection's fd close().
Many different threads compete frequently for the epmutex lock,
affecting the overall performance.
To reduce the contention this patch introduces explicit reference counting
for the eventpoll struct. Each registered event acquires a reference,
and references are released at ep_remove() time.
The eventpoll struct is released by whoever - among EP file close() and
and the monitored file close() drops its last reference.
Additionally, this introduces a new 'dying' flag to prevent races between
the EP file close() and the monitored file close().
ep_eventpoll_release() marks, under f_lock spinlock, each epitem as dying
before removing it, while EP file close() does not touch dying epitems.
The above is needed as both close operations could run concurrently and
drop the EP reference acquired via the epitem entry. Without the above
flag, the monitored file close() could reach the EP struct via the epitem
list while the epitem is still listed and then try to put it after its
disposal.
An alternative could be avoiding touching the references acquired via
the epitems at EP file close() time, but that could leave the EP struct
alive for potentially unlimited time after EP file close(), with nasty
side effects.
With all the above in place, we can drop the epmutex usage at disposal time.
Overall this produces a significant performance improvement in the
mentioned connection/rate scenario: the mutex operations disappear from
the topmost offenders in the perf report, and the measured connections/rate
grows by ~60%.
To make the change more readable this additionally renames ep_free() to
ep_clear_and_put(), and moves the actual memory cleanup in a separate
ep_free() helper.
Link: https://lkml.kernel.org/r/4a57788dcaf28f5eb4f8dfddcc3a8b172a7357bb.1679504153.git.pabeni@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Co-developed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Xiumei Mu <xmu@redhiat.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Jacob Keller <jacob.e.keller@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This doesn't make any sense to expose to userspace, so it's been moved
to the one user. This was introduced by commit 95f19f658c ("epoll:
drop EPOLLWAKEUP if PM_SLEEP is disabled").
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Reviewed-by: Andrew Waterman <waterman@eecs.berkeley.edu>
Reviewed-by: Albert Ou <aou@eecs.berkeley.edu>
Message-Id: <1447119071-19392-7-git-send-email-palmer@dabbelt.com>
[thuth: Rebased to fix contextual conflicts]
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
We can have dependencies between epoll and io_uring. Consider an epoll
context, identified by the epfd file descriptor, and an io_uring file
descriptor identified by iofd. If we add iofd to the epfd context, and
arm a multishot poll request for epfd with iofd, then the multishot
poll request will repeatedly trigger and generate events until terminated
by CQ ring overflow. This isn't a desired behavior.
Add EPOLL_URING so that io_uring can pass it in as part of the poll wakeup
key, and io_uring can check for that to detect a potential recursive
invocation.
Cc: stable@vger.kernel.org # 6.0
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
list_add_tail_lockless. x86 CMPXCHG instruction returns success in ZF
flag, so this change saves a compare after cmpxchg (and related move
instruction in front of cmpxchg).
No functional change intended.
Link: https://lkml.kernel.org/r/20220714173255.12987-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
If a process is killed or otherwise exits while having active network
connections and many threads waiting on epoll_wait, the threads will all
be woken immediately, but not removed from ep->wq. Then when network
traffic scans ep->wq in wake_up, every wakeup attempt will fail, and will
not remove the entries from the list.
This means that the cost of the wakeup attempt is far higher than usual,
does not decrease, and this also competes with the dying threads trying to
actually make progress and remove themselves from the wq.
Handle this by removing visited epoll wq entries unconditionally, rather
than only when the wakeup succeeds - the structure of ep_poll means that
the only potential loss is the timed_out->eavail heuristic, which now can
race and result in a redundant ep_send_events attempt. (But only when
incoming data and a timeout actually race, not on every timeout)
Shakeel added:
: We are seeing this issue in production with real workloads and it has
: caused hard lockups. Particularly network heavy workloads with a lot
: of threads in epoll_wait() can easily trigger this issue if they get
: killed (oom-killed in our case).
Link: https://lkml.kernel.org/r/xm26fsjotqda.fsf@google.com
Signed-off-by: Ben Segall <bsegall@google.com>
Tested-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Roman Penyaev <rpenyaev@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Khazhismel Kumykov <khazhy@google.com>
Cc: Heiher <r@hev.cc>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.
To help with this maintenance let's start by moving sysctls to places
where they actually belong. The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.
So move the epoll_table sysctl to fs/eventpoll.c and use
register_sysctl().
Link: https://lkml.kernel.org/r/20211123202422.819032-9-mcgrof@kernel.org
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: David Airlie <airlied@linux.ie>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Phillip Potter <phil@philpotter.co.uk>
Cc: Qing Wang <wangqing@vivo.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: James E.J. Bottomley <jejb@linux.ibm.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This counter tracks the number of watches a user has, to compare against
the 'max_user_watches' limit. This causes a scalability bottleneck on
SPECjbb2015 on large systems as there is only one user. Changing to a
per-cpu counter increases throughput of the benchmark by about 30% on a
16-socket, > 1000 thread system.
[rdunlap@infradead.org: fix build errors in kernel/user.c when CONFIG_EPOLL=n]
[npiggin@gmail.com: move ifdefs into wrapper functions, slightly improve panic message]
Link: https://lkml.kernel.org/r/1628051945.fens3r99ox.astroid@bobo.none
[akpm@linux-foundation.org: tweak user_epoll_alloc(), per Guenter]
Link: https://lkml.kernel.org/r/20210804191421.GA1900577@roeck-us.net
Link: https://lkml.kernel.org/r/20210802032013.2751916-1-npiggin@gmail.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reported-by: Anton Blanchard <anton@ozlabs.org>
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>
The epoll_wait() system call wrapper is one of the remaining users of
the set_fs() infrasturcture for Arm. Changing it to not require set_fs()
is rather complex unfortunately.
The approach I'm taking here is to allow architectures to override
the code that copies the output to user space, and let the oabi-compat
implementation check whether it is getting called from an EABI or OABI
system call based on the thread_info->syscall value.
The in_oabi_syscall() check here mirrors the in_compat_syscall() and
in_x32_syscall() helpers for 32-bit compat implementations on other
architectures.
Overall, the amount of code goes down, at least with the newly added
sys_oabi_epoll_pwait() helper getting removed again. The downside
is added complexity in the source code for the native implementation.
There should be no difference in runtime performance except for Arm
kernels with CONFIG_OABI_COMPAT enabled that now have to go through
an external function call to check which of the two variants to use.
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Commit 339ddb53d3 ("fs/epoll: remove unnecessary wakeups of nested
epoll") changed the userspace visible behavior of exclusive waiters
blocked on a common epoll descriptor upon a single event becoming ready.
Previously, all tasks doing epoll_wait would awake, and now only one is
awoken, potentially causing missed wakeups on applications that rely on
this behavior, such as Apache Qpid.
While the aforementioned commit aims at having only a wakeup single path
in ep_poll_callback (with the exceptions of epoll_ctl cases), we need to
restore the wakeup in what was the old ep_scan_ready_list() such that
the next thread can be awoken, in a cascading style, after the waker's
corresponding ep_send_events().
Link: https://lkml.kernel.org/r/20210405231025.33829-3-dave@stgolabs.net
Fixes: 339ddb53d3 ("fs/epoll: remove unnecessary wakeups of nested epoll")
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Roman Penyaev <rpenyaev@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use the documented kernel-doc format for function Return: descriptions.
Begin constant values in kernel-doc comments with '%'.
Remove kernel-doc "/**" from 2 functions that are not documented with
kernel-doc notation.
Fix typos, punctuation, & grammar.
Also fix a few kernel-doc warnings:
../fs/eventpoll.c:1883: warning: Function parameter or member 'ep' not described in 'ep_loop_check_proc'
../fs/eventpoll.c:1883: warning: Excess function parameter 'priv' description in 'ep_loop_check_proc'
../fs/eventpoll.c:1932: warning: Function parameter or member 'ep' not described in 'ep_loop_check'
../fs/eventpoll.c:1932: warning: Excess function parameter 'from' description in 'ep_loop_check'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Userspace has discovered the functionality offered by SYS_kcmp and has
started to depend upon it. In particular, Mesa uses SYS_kcmp for
os_same_file_description() in order to identify when two fd (e.g. device
or dmabuf) point to the same struct file. Since they depend on it for
core functionality, lift SYS_kcmp out of the non-default
CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to
deduplicate the per-service file descriptor store.
Note that some distributions such as Ubuntu are already enabling
CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: stable@vger.kernel.org
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> # DRM depends on kcmp
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> # systemd uses kcmp
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210205220012.1983-1-chris@chris-wilson.co.uk
Add syscall epoll_pwait2, an epoll_wait variant with nsec resolution that
replaces int timeout with struct timespec. It is equivalent otherwise.
int epoll_pwait2(int fd, struct epoll_event *events,
int maxevents,
const struct timespec *timeout,
const sigset_t *sigset);
The underlying hrtimer is already programmed with nsec resolution.
pselect and ppoll also set nsec resolution timeout with timespec.
The sigset_t in epoll_pwait has a compat variant. epoll_pwait2 needs
the same.
For timespec, only support this new interface on 2038 aware platforms
that define __kernel_timespec_t. So no CONFIG_COMPAT_32BIT_TIME.
Link: https://lkml.kernel.org/r/20201121144401.3727659-3-willemdebruijn.kernel@gmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "add epoll_pwait2 syscall", v4.
Enable nanosecond timeouts for epoll.
Analogous to pselect and ppoll, introduce an epoll_wait syscall
variant that takes a struct timespec instead of int timeout.
This patch (of 4):
Make epoll more consistent with select/poll: pass along the timeout as
timespec64 pointer.
In anticipation of additional changes affecting all three polling
mechanisms:
- add epoll_pwait2 syscall with timespec semantics,
and share poll_select_set_timeout implementation.
- compute slack before conversion to absolute time,
to save one ktime_get_ts64 call.
Link: https://lkml.kernel.org/r/20201121144401.3727659-1-willemdebruijn.kernel@gmail.com
Link: https://lkml.kernel.org/r/20201121144401.3727659-2-willemdebruijn.kernel@gmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We call ep_events_available() under lock when timeout is 0, and then call
it without locks in the loop for the other cases.
Instead, call ep_events_available() without lock for all cases. For
non-zero timeouts, we will recheck after adding the thread to the wait
queue. For zero timeout cases, by definition, user is opportunistically
polling and will have to call epoll_wait again in the future.
Note that this lock was kept in c5a282e963 because the whole loop was
historically under lock.
This patch results in a 1% CPU/RPC reduction in RPC benchmarks.
Link: https://lkml.kernel.org/r/20201106231635.3528496-9-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The existing loop is pointless, and the labels make it really hard to
follow the structure.
Replace that control structure with a simple loop that returns when there
are new events, there is a signal, or the thread has timed out.
Link: https://lkml.kernel.org/r/20201106231635.3528496-8-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a no-op change which simplifies the follow up patches.
Link: https://lkml.kernel.org/r/20201106231635.3528496-7-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ep_events_available() is called multiple times around the busy loop logic,
even though the logic is generally not used. ep_reset_busy_poll_napi_id()
is similarly always called, even when busy loop is not used.
Eliminate ep_reset_busy_poll_napi_id() and inline it inside
ep_busy_loop(). Make ep_busy_loop() return whether there are any events
available after the busy loop. This will eliminate unnecessary loads and
branches, and simplifies the loop.
Link: https://lkml.kernel.org/r/20201106231635.3528496-6-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a no-op change and simply to make the code more coherent.
Link: https://lkml.kernel.org/r/20201106231635.3528496-5-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To simplify the code, pull in checking the fatal signals into
ep_send_events(). ep_send_events() is called only from ep_poll().
Note that, previously, we were always checking fatal events, but it is
checked only if eavail is true. This should be fine because the goal of
that check is to quickly return from epoll_wait() when there is a pending
fatal signal.
Link: https://lkml.kernel.org/r/20201106231635.3528496-4-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Check signals before locking ep->lock, and immediately return -EINTR if
there is any signal pending.
This saves a few loads, stores, and branches from the hot path and
simplifies the loop structure for follow up patches.
Link: https://lkml.kernel.org/r/20201106231635.3528496-3-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "simplify ep_poll".
This patch series is a followup based on the suggestions and feedback by
Linus:
https://lkml.kernel.org/r/CAHk-=wizk=OxUyQPbO8MS41w2Pag1kniUV5WdD5qWL-gq1kjDA@mail.gmail.com
The first patch in the series is a fix for the epoll race in presence of
timeouts, so that it can be cleanly backported to all affected stable
kernels.
The rest of the patch series simplify the ep_poll() implementation. Some
of these simplifications result in minor performance enhancements as well.
We have kept these changes under self tests and internal benchmarks for a
few days, and there are minor (1-2%) performance enhancements as a result.
This patch (of 8):
After abc610e01c ("fs/epoll: avoid barrier after an epoll_wait(2)
timeout"), we break out of the ep_poll loop upon timeout, without checking
whether there is any new events available. Prior to that patch-series we
always called ep_events_available() after exiting the loop.
This can cause races and missed wakeups. For example, consider the
following scenario reported by Guantao Liu:
Suppose we have an eventfd added using EPOLLET to an epollfd.
Thread 1: Sleeps for just below 5ms and then writes to an eventfd.
Thread 2: Calls epoll_wait with a timeout of 5 ms. If it sees an
event of the eventfd, it will write back on that fd.
Thread 3: Calls epoll_wait with a negative timeout.
Prior to abc610e01c, it is guaranteed that Thread 3 will wake up either
by Thread 1 or Thread 2. After abc610e01c, Thread 3 can be blocked
indefinitely if Thread 2 sees a timeout right before the write to the
eventfd by Thread 1. Thread 2 will be woken up from
schedule_hrtimeout_range and, with evail 0, it will not call
ep_send_events().
To fix this issue:
1) Simplify the timed_out case as suggested by Linus.
2) while holding the lock, recheck whether the thread was woken up
after its time out has reached.
Note that (2) is different from Linus' original suggestion: It do not set
"eavail = ep_events_available(ep)" to avoid unnecessary contention (when
there are too many timed-out threads and a small number of events), as
well as races mentioned in the discussion thread.
This is the first patch in the series so that the backport to stable
releases is straightforward.
Link: https://lkml.kernel.org/r/20201106231635.3528496-1-soheil.kdev@gmail.com
Link: https://lkml.kernel.org/r/CAHk-=wizk=OxUyQPbO8MS41w2Pag1kniUV5WdD5qWL-gq1kjDA@mail.gmail.com
Link: https://lkml.kernel.org/r/20201106231635.3528496-2-soheil.kdev@gmail.com
Fixes: abc610e01c ("fs/epoll: avoid barrier after an epoll_wait(2) timeout")
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Tested-by: Guantao Liu <guantaol@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Guantao Liu <guantaol@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull epoll updates from Al Viro:
"Deal with epoll loop check/removal races sanely (among other things).
The solution merged last cycle (pinning a bunch of struct file
instances) had been forced by the wrong data structures; untangling
that takes a bunch of preparations, but it's worth doing - control
flow in there is ridiculously overcomplicated. Memory footprint has
also gone down, while we are at it.
This is not all I want to do in the area, but since I didn't get
around to posting the followups they'll have to wait for the next
cycle"
* 'work.epoll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (27 commits)
epoll: take epitem list out of struct file
epoll: massage the check list insertion
lift rcu_read_lock() into reverse_path_check()
convert ->f_ep_links/->fllink to hlist
ep_insert(): move creation of wakeup source past the fl_ep_links insertion
fold ep_read_events_proc() into the only caller
take the common part of ep_eventpoll_poll() and ep_item_poll() into helper
ep_insert(): we only need tep->mtx around the insertion itself
ep_insert(): don't open-code ep_remove() on failure exits
lift locking/unlocking ep->mtx out of ep_{start,done}_scan()
ep_send_events_proc(): fold into the caller
lift the calls of ep_send_events_proc() into the callers
lift the calls of ep_read_events_proc() into the callers
ep_scan_ready_list(): prepare to splitup
ep_loop_check_proc(): saner calling conventions
get rid of ep_push_nested()
ep_loop_check_proc(): lift pushing the cookie into callers
clean reverse_path_check_proc() a bit
reverse_path_check_proc(): don't bother with cookies
reverse_path_check_proc(): sane arguments
...
Currently, the sock_from_file prototype takes an "err" pointer that is
either not set or set to -ENOTSOCK IFF the returned socket is NULL. This
makes the error redundant and it is ignored by a few callers.
This patch simplifies the API by letting callers deduce the error based
on whether the returned socket is NULL or not.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Florent Revest <revest@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: KP Singh <kpsingh@google.com>
Link: https://lore.kernel.org/bpf/20201204113609.1850150-1-revest@google.com
This option lets a user set a per socket NAPI budget for
busy-polling. If the options is not set, it will use the default of 8.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20201130185205.196029-3-bjorn.topel@gmail.com
The existing busy-polling mode, enabled by the SO_BUSY_POLL socket
option or system-wide using the /proc/sys/net/core/busy_read knob, is
an opportunistic. That means that if the NAPI context is not
scheduled, it will poll it. If, after busy-polling, the budget is
exceeded the busy-polling logic will schedule the NAPI onto the
regular softirq handling.
One implication of the behavior above is that a busy/heavy loaded NAPI
context will never enter/allow for busy-polling. Some applications
prefer that most NAPI processing would be done by busy-polling.
This series adds a new socket option, SO_PREFER_BUSY_POLL, that works
in concert with the napi_defer_hard_irqs and gro_flush_timeout
knobs. The napi_defer_hard_irqs and gro_flush_timeout knobs were
introduced in commit 6f8b12d661 ("net: napi: add hard irqs deferral
feature"), and allows for a user to defer interrupts to be enabled and
instead schedule the NAPI context from a watchdog timer. When a user
enables the SO_PREFER_BUSY_POLL, again with the other knobs enabled,
and the NAPI context is being processed by a softirq, the softirq NAPI
processing will exit early to allow the busy-polling to be performed.
If the application stops performing busy-polling via a system call,
the watchdog timer defined by gro_flush_timeout will timeout, and
regular softirq handling will resume.
In summary; Heavy traffic applications that prefer busy-polling over
softirq processing should use this option.
Example usage:
$ echo 2 | sudo tee /sys/class/net/ens785f1/napi_defer_hard_irqs
$ echo 200000 | sudo tee /sys/class/net/ens785f1/gro_flush_timeout
Note that the timeout should be larger than the userspace processing
window, otherwise the watchdog will timeout and fall back to regular
softirq processing.
Enable the SO_BUSY_POLL/SO_PREFER_BUSY_POLL options on your socket.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20201130185205.196029-2-bjorn.topel@gmail.com
Move the head of epitem list out of struct file; for epoll ones it's
moved into struct eventpoll (->refs there), for non-epoll - into
the new object (struct epitem_head). In place of ->f_ep_links we
leave a pointer to the list head (->f_ep).
->f_ep is protected by ->f_lock and it's zeroed as soon as the list
of epitems becomes empty (that can happen only in ep_remove() by
now).
The list of files for reverse path check is *not* going through
struct file now - it's a single-linked list going through epitem_head
instances. It's terminated by ERR_PTR(-1) (== EP_UNACTIVE_POINTER),
so the elements of list can be distinguished by head->next != NULL.
epitem_head instances are allocated at ep_insert() time (by
attach_epitem()) and freed either by ep_remove() (if it empties
the set of epitems *and* epitem_head does not belong to the
reverse path check list) or by clear_tfile_check_list() when
the list is emptied (if the set of epitems is empty by that
point). Allocations are done from a separate slab - minimal kmalloc()
size is too large on some architectures.
As the result, we trim struct file _and_ get rid of the games with
temporary file references.
Locking and barriers are interesting (aren't they always); see unlist_file()
and ep_remove() for details. The non-obvious part is that ep_remove() needs
to decide if it will be the one to free the damn thing *before* actually
storing NULL to head->epitems.first - that's what smp_load_acquire is for
in there. unlist_file() lockless path is safe, since we hit it only if
we observe NULL in head->epitems.first and whoever had done that store is
guaranteed to have observed non-NULL in head->next. IOW, their last access
had been the store of NULL into ->epitems.first and we can safely free
the sucker. OTOH, we are under rcu_read_lock() and both epitem and
epitem->file have their freeing RCU-delayed. So if we see non-NULL
->epitems.first, we can grab ->f_lock (all epitems in there share the
same struct file) and safely recheck the emptiness of ->epitems; again,
->next is still non-NULL, so ep_remove() couldn't have freed head yet.
->f_lock serializes us wrt ep_remove(); the rest is trivial.
Note that once head->epitems becomes NULL, nothing can get inserted into
it - the only remaining reference to head after that point is from the
reverse path check list.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
in the "non-epoll target" cases do it in ep_insert() rather than
in do_epoll_ctl(), so that we do it only with some epitem is already
guaranteed to exist.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
That's the beginning of preparations for taking f_ep_links out of struct file.
If insertion might fail, we will need a new failure exit. Having wakeup
source creation done after that point will simplify life there; ep_remove()
can (and commonly does) live with NULL epi->ws, so it can be used for
cleanup after ep_create_wakeup_source() failure. It can't be used before
the rbtree insertion, though, so if we are to unify all old failure exits,
we need to move that thing down. Then we would be free to do simple
kmem_cache_free() on the failure to insert into f_ep_links - no wakeup source
to leak on that failure exit.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The only reason why ep_item_poll() can't simply call ep_eventpoll_poll()
(or, better yet, call vfs_poll() in all cases) is that we need to tell
lockdep how deep into the hierarchy of ->mtx we are. So let's add
a variant of ep_eventpoll_poll() that would take depth explicitly
and turn ep_eventpoll_poll() into wrapper for that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
We do need ep->mtx (and we are holding it all along), but that's
the lock on the epoll we are inserting into; locking of the
epoll being inserted is not needed for most of that work -
as the matter of fact, we only need it to provide barriers
for the fastpath check (for now).
Move taking and releasing it into ep_insert(). The caller
(do_epoll_ctl()) doesn't need to bother with that at all.
Moreover, that way we kill the kludge in ep_item_poll() - now
it's always called with tep unlocked.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
get rid of depth/ep_locked arguments there and document
the kludge in ep_item_poll() that has lead to ep_locked existence in
the first place
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... and get rid of struct ep_send_events_data - not needed anymore.
The weird way of passing the arguments in (and real return value
out - nominal return value of ep_send_events_proc() is ignored)
was due to the signature forced on ep_scan_ready_list() callbacks.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Expand the calls of ep_scan_ready_list() that get ep_read_events_proc().
As a side benefit we can pass depth to ep_read_events_proc() by value
and not by address - the latter used to be forced by the signature
expected from ep_scan_ready_list() callback.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1) 'cookie' argument is unused; kill it.
2) 'priv' one is always an epoll struct file, and we only care
about its associated struct eventpoll; pass that instead.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
