Linus Torvalds [Sat, 7 Nov 2015 22:32:45 +0000 (14:32 -0800)]
Merge branch 'akpm' (patches from Andrew)
Merge second patch-bomb from Andrew Morton:
- most of the rest of MM
- procfs
- lib/ updates
- printk updates
- bitops infrastructure tweaks
- checkpatch updates
- nilfs2 update
- signals
- various other misc bits: coredump, seqfile, kexec, pidns, zlib, ipc,
dma-debug, dma-mapping, ...
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (102 commits)
ipc,msg: drop dst nil validation in copy_msg
include/linux/zutil.h: fix usage example of zlib_adler32()
panic: release stale console lock to always get the logbuf printed out
dma-debug: check nents in dma_sync_sg*
dma-mapping: tidy up dma_parms default handling
pidns: fix set/getpriority and ioprio_set/get in PRIO_USER mode
kexec: use file name as the output message prefix
fs, seqfile: always allow oom killer
seq_file: reuse string_escape_str()
fs/seq_file: use seq_* helpers in seq_hex_dump()
coredump: change zap_threads() and zap_process() to use for_each_thread()
coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP
signal: remove jffs2_garbage_collect_thread()->allow_signal(SIGCONT)
signal: introduce kernel_signal_stop() to fix jffs2_garbage_collect_thread()
signal: turn dequeue_signal_lock() into kernel_dequeue_signal()
signals: kill block_all_signals() and unblock_all_signals()
nilfs2: fix gcc uninitialized-variable warnings in powerpc build
nilfs2: fix gcc unused-but-set-variable warnings
MAINTAINERS: nilfs2: add header file for tracing
nilfs2: add tracepoints for analyzing reading and writing metadata files
...
Linus Torvalds [Sat, 7 Nov 2015 21:33:07 +0000 (13:33 -0800)]
Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma
Pull rdma updates from Doug Ledford:
"This is my initial round of 4.4 merge window patches. There are a few
other things I wish to get in for 4.4 that aren't in this pull, as
this represents what has gone through merge/build/run testing and not
what is the last few items for which testing is not yet complete.
- "Checksum offload support in user space" enablement
- Misc cxgb4 fixes, add T6 support
- Misc usnic fixes
- 32 bit build warning fixes
- Misc ocrdma fixes
- Multicast loopback prevention extension
- Extend the GID cache to store and return attributes of GIDs
- Misc iSER updates
- iSER clustering update
- Network NameSpace support for rdma CM
- Work Request cleanup series
- New Memory Registration API"
* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma: (76 commits)
IB/core, cma: Make __attribute_const__ declarations sparse-friendly
IB/core: Remove old fast registration API
IB/ipath: Remove fast registration from the code
IB/hfi1: Remove fast registration from the code
RDMA/nes: Remove old FRWR API
IB/qib: Remove old FRWR API
iw_cxgb4: Remove old FRWR API
RDMA/cxgb3: Remove old FRWR API
RDMA/ocrdma: Remove old FRWR API
IB/mlx4: Remove old FRWR API support
IB/mlx5: Remove old FRWR API support
IB/srp: Dont allocate a page vector when using fast_reg
IB/srp: Remove srp_finish_mapping
IB/srp: Convert to new registration API
IB/srp: Split srp_map_sg
RDS/IW: Convert to new memory registration API
svcrdma: Port to new memory registration API
xprtrdma: Port to new memory registration API
iser-target: Port to new memory registration API
IB/iser: Port to new fast registration API
...
Linus Torvalds [Sat, 7 Nov 2015 21:05:44 +0000 (13:05 -0800)]
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial
Pull trivial updates from Jiri Kosina:
"Trivial stuff from trivial tree that can be trivially summed up as:
- treewide drop of spurious unlikely() before IS_ERR() from Viresh
Kumar
- cosmetic fixes (that don't really affect basic functionality of the
driver) for pktcdvd and bcache, from Julia Lawall and Petr Mladek
- various comment / printk fixes and updates all over the place"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial:
bcache: Really show state of work pending bit
hwmon: applesmc: fix comment typos
Kconfig: remove comment about scsi_wait_scan module
class_find_device: fix reference to argument "match"
debugfs: document that debugfs_remove*() accepts NULL and error values
net: Drop unlikely before IS_ERR(_OR_NULL)
mm: Drop unlikely before IS_ERR(_OR_NULL)
fs: Drop unlikely before IS_ERR(_OR_NULL)
drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
drivers: misc: Drop unlikely before IS_ERR(_OR_NULL)
UBI: Update comments to reflect UBI_METAONLY flag
pktcdvd: drop null test before destroy functions
Linus Torvalds [Sat, 7 Nov 2015 20:15:17 +0000 (12:15 -0800)]
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching
Pull livepatching fix from Jiri Kosina:
"A fix for a kernel oops in case CONFIG_DEBUG_SET_MODULE_RONX is unset
(as in such case it's possible for module struct to share a page with
executable text, which is currently not being handled with grace) from
Josh Poimboeuf"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching:
livepatch: Fix crash with !CONFIG_DEBUG_SET_MODULE_RONX
Davidlohr Bueso [Sat, 7 Nov 2015 00:33:04 +0000 (16:33 -0800)]
ipc,msg: drop dst nil validation in copy_msg
d0edd8528362 ("ipc: convert invalid scenarios to use WARN_ON") relaxed the
nil dst parameter check, originally being a full BUG_ON. However, this
check seems quite unnecessary when the only purpose is for
ceckpoint/restore (MSG_COPY flag):
o The copy variable is set initially to nil, apparently as a way of
ensuring that prepare_copy is previously called. Which is in fact done,
unconditionally at the beginning of do_msgrcv.
o There is no concurrency with 'copy' (stack allocated in do_msgrcv).
Furthermore, any errors in 'copy' (and thus prepare_copy/copy_msg) should
always handled by IS_ERR() family. Therefore remove this check altogether
as it can never occur with the current users.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Stanislav Kinsbursky <skinsbursky@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
panic: release stale console lock to always get the logbuf printed out
In some cases we may end up killing the CPU holding the console lock
while still having valuable data in logbuf. E.g. I'm observing the
following:
- A crash is happening on one CPU and console_unlock() is being called on
some other.
- console_unlock() tries to print out the buffer before releasing the lock
and on slow console it takes time.
- in the meanwhile crashing CPU does lots of printk()-s with valuable data
(which go to the logbuf) and sends IPIs to all other CPUs.
- console_unlock() finishes printing previous chunk and enables interrupts
before trying to print out the rest, the CPU catches the IPI and never
releases console lock.
This is not the only possible case: in VT/fb subsystems we have many other
console_lock()/console_unlock() users. Non-masked interrupts (or
receiving NMI in case of extreme slowness) will have the same result.
Getting the whole console buffer printed out on crash should be top
priority.
Robin Murphy [Sat, 7 Nov 2015 00:32:55 +0000 (16:32 -0800)]
dma-debug: check nents in dma_sync_sg*
Like dma_unmap_sg, dma_sync_sg* should be called with the original number
of entries passed to dma_map_sg, so do the same check in the sync path as
we do in the unmap path.
Signed-off-by: Robin Murphy <robin.murphy@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Sakari Ailus <sakari.ailus@iki.fi> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Robin Murphy [Sat, 7 Nov 2015 00:32:51 +0000 (16:32 -0800)]
dma-mapping: tidy up dma_parms default handling
Many DMA controllers and other devices set max_segment_size to
indicate their scatter-gather capability, but have no interest in
segment_boundary_mask. However, the existence of a dma_parms structure
precludes the use of any default value, leaving them as zeros (assuming
a properly kzalloc'ed structure). If a well-behaved IOMMU (or SWIOTLB)
then tries to respect this by ensuring a mapped segment does not cross
a zero-byte boundary, hilarity ensues.
Since zero is a nonsensical value for either parameter, treat it as an
indicator for "default", as might be expected. In the process, clean up
a bit by replacing the bare constants with slightly more meaningful
macros and removing the superfluous "else" statements.
[akpm@linux-foundation.org: dma-mapping.h needs sizes.h for SZ_64K] Signed-off-by: Robin Murphy <robin.murphy@arm.com> Reviewed-by: Sumit Semwal <sumit.semwal@linaro.org> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Sakari Ailus <sakari.ailus@iki.fi> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Ben Segall [Sat, 7 Nov 2015 00:32:48 +0000 (16:32 -0800)]
pidns: fix set/getpriority and ioprio_set/get in PRIO_USER mode
setpriority(PRIO_USER, 0, x) will change the priority of tasks outside of
the current pid namespace. This is in contrast to both the other modes of
setpriority and the example of kill(-1). Fix this. getpriority and
ioprio have the same failure mode, fix them too.
Eric said:
: After some more thinking about it this patch sounds justifiable.
:
: My goal with namespaces is not to build perfect isolation mechanisms
: as that can get into ill defined territory, but to build well defined
: mechanisms. And to handle the corner cases so you can use only
: a single namespace with well defined results.
:
: In this case you have found the two interfaces I am aware of that
: identify processes by uid instead of by pid. Which quite frankly is
: weird. Unfortunately the weird unexpected cases are hard to handle
: in the usual way.
:
: I was hoping for a little more information. Changes like this one we
: have to be careful of because someone might be depending on the current
: behavior. I don't think they are and I do think this make sense as part
: of the pid namespace.
Signed-off-by: Ben Segall <bsegall@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ambrose Feinstein <ambrose@google.com> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Minfei Huang [Sat, 7 Nov 2015 00:32:45 +0000 (16:32 -0800)]
kexec: use file name as the output message prefix
kexec output message misses the prefix "kexec", when Dave Young split the
kexec code. Now, we use file name as the output message prefix.
Currently, the format of output message:
[ 140.290795] SYSC_kexec_load: hello, world
[ 140.291534] kexec: sanity_check_segment_list: hello, world
Ideally, the format of output message:
[ 30.791503] kexec: SYSC_kexec_load, Hello, world
[ 79.182752] kexec_core: sanity_check_segment_list, Hello, world
Remove the custom prefix "kexec" in output message.
Signed-off-by: Minfei Huang <mnfhuang@gmail.com> Acked-by: Dave Young <dyoung@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Greg Thelen [Sat, 7 Nov 2015 00:32:42 +0000 (16:32 -0800)]
fs, seqfile: always allow oom killer
Since 5cec38ac866b ("fs, seq_file: fallback to vmalloc instead of oom kill
processes") seq_buf_alloc() avoids calling the oom killer for PAGE_SIZE or
smaller allocations; but larger allocations can use the oom killer via
vmalloc(). Thus reads of small files can return ENOMEM, but larger files
use the oom killer to avoid ENOMEM.
The effect of this bug is that reads from /proc and other virtual
filesystems can return ENOMEM instead of the preferred behavior - oom
killing something (possibly the calling process). I don't know of anyone
except Google who has noticed the issue.
I suspect the fix is more needed in smaller systems where there isn't any
reclaimable memory. But these seem like the kinds of systems which
probably don't use the oom killer for production situations.
Memory overcommit requires use of the oom killer to select a victim
regardless of file size.
Enable oom killer for small seq_buf_alloc() allocations.
Fixes: 5cec38ac866b ("fs, seq_file: fallback to vmalloc instead of oom kill processes") Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Greg Thelen <gthelen@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy Shevchenko [Sat, 7 Nov 2015 00:32:40 +0000 (16:32 -0800)]
seq_file: reuse string_escape_str()
strint_escape_str() escapes input string by given criteria. In case of
seq_escape() the criteria is to convert some characters to their octal
representation.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@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>
Oleg Nesterov [Sat, 7 Nov 2015 00:32:31 +0000 (16:32 -0800)]
coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP
task_will_free_mem() is wrong in many ways, and in particular the
SIGNAL_GROUP_COREDUMP check is not reliable: a task can participate in the
coredumping without SIGNAL_GROUP_COREDUMP bit set.
change zap_threads() paths to always set SIGNAL_GROUP_COREDUMP even if
other CLONE_VM processes can't react to SIGKILL. Fortunately, at least
oom-kill case if fine; it kills all tasks sharing the same mm, so it
should also kill the process which actually dumps the core.
The change in prepare_signal() is not strictly necessary, it just ensures
that the patch does not bring another subtle behavioural change. But it
reminds us that this SIGNAL_GROUP_EXIT/COREDUMP case needs more changes.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Kyle Walker <kwalker@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Stanislav Kozina <skozina@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Oleg Nesterov [Sat, 7 Nov 2015 00:32:25 +0000 (16:32 -0800)]
signal: introduce kernel_signal_stop() to fix jffs2_garbage_collect_thread()
jffs2_garbage_collect_thread() can race with SIGCONT and sleep in
TASK_STOPPED state after it was already sent. Add the new helper,
kernel_signal_stop(), which does this correctly.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Felipe Balbi <balbi@ti.com> Cc: Markus Pargmann <mpa@pengutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Oleg Nesterov [Sat, 7 Nov 2015 00:32:22 +0000 (16:32 -0800)]
signal: turn dequeue_signal_lock() into kernel_dequeue_signal()
1. Rename dequeue_signal_lock() to kernel_dequeue_signal(). This
matches another "for kthreads only" kernel_sigaction() helper.
2. Remove the "tsk" and "mask" arguments, they are always current
and current->blocked. And it is simply wrong if tsk != current.
3. We could also remove the 3rd "siginfo_t *info" arg but it looks
potentially useful. However we can simplify the callers if we
change kernel_dequeue_signal() to accept info => NULL.
4. Remove _irqsave, it is never called from atomic context.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Felipe Balbi <balbi@ti.com> Cc: Markus Pargmann <mpa@pengutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Oleg Nesterov [Sat, 7 Nov 2015 00:32:19 +0000 (16:32 -0800)]
signals: kill block_all_signals() and unblock_all_signals()
It is hardly possible to enumerate all problems with block_all_signals()
and unblock_all_signals(). Just for example,
1. block_all_signals(SIGSTOP/etc) simply can't help if the caller is
multithreaded. Another thread can dequeue the signal and force the
group stop.
2. Even is the caller is single-threaded, it will "stop" anyway. It
will not sleep, but it will spin in kernel space until SIGCONT or
SIGKILL.
And a lot more. In short, this interface doesn't work at all, at least
the last 10+ years.
Daniel said:
Yeah the only times I played around with the DRM_LOCK stuff was when
old drivers accidentally deadlocked - my impression is that the entire
DRM_LOCK thing was never really tested properly ;-) Hence I'm all for
purging where this leaks out of the drm subsystem.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Dave Airlie <airlied@redhat.com> Cc: Richard Weinberger <richard@nod.at> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Ryusuke Konishi [Sat, 7 Nov 2015 00:32:16 +0000 (16:32 -0800)]
nilfs2: fix gcc uninitialized-variable warnings in powerpc build
Some false positive warnings are reported for powerpc build.
The following warnings are reported in
http://kisskb.ellerman.id.au/kisskb/buildresult/12519703/
CC fs/nilfs2/super.o
fs/nilfs2/super.c: In function 'nilfs_resize_fs':
fs/nilfs2/super.c:376:2: warning: 'blocknr' may be used uninitialized in this function [-Wuninitialized]
fs/nilfs2/super.c:362:11: note: 'blocknr' was declared here
CC fs/nilfs2/recovery.o
fs/nilfs2/recovery.c: In function 'nilfs_salvage_orphan_logs':
fs/nilfs2/recovery.c:631:21: warning: 'sum' may be used uninitialized in this function [-Wuninitialized]
fs/nilfs2/recovery.c:585:32: note: 'sum' was declared here
fs/nilfs2/recovery.c: In function 'nilfs_search_super_root':
fs/nilfs2/recovery.c:873:11: warning: 'sum' may be used uninitialized in this function [-Wuninitialized]
Another similar warning is reported in
http://kisskb.ellerman.id.au/kisskb/buildresult/12520079/
CC fs/nilfs2/btree.o
fs/nilfs2/btree.c: In function 'nilfs_btree_convert_and_insert':
include/asm-generic/bitops/non-atomic.h:105:20: warning: 'bh' may be used uninitialized in this function [-Wuninitialized]
fs/nilfs2/btree.c:1859:22: note: 'bh' was declared here
This cleans out these warnings by forcing the variables to be initialized.
Ryusuke Konishi [Sat, 7 Nov 2015 00:32:14 +0000 (16:32 -0800)]
nilfs2: fix gcc unused-but-set-variable warnings
Fix the following build warnings:
$ make W=1
[...]
CC [M] fs/nilfs2/btree.o
fs/nilfs2/btree.c: In function 'nilfs_btree_split':
fs/nilfs2/btree.c:923:8: warning: variable 'newptr' set but not used [-Wunused-but-set-variable]
__u64 newptr;
^
fs/nilfs2/btree.c:922:8: warning: variable 'newkey' set but not used [-Wunused-but-set-variable]
__u64 newkey;
^
CC [M] fs/nilfs2/dat.o
fs/nilfs2/dat.c: In function 'nilfs_dat_prepare_end':
fs/nilfs2/dat.c:158:8: warning: variable 'start' set but not used [-Wunused-but-set-variable]
__u64 start;
^
CC [M] fs/nilfs2/segment.o
fs/nilfs2/segment.c: In function 'nilfs_segctor_do_immediate_flush':
fs/nilfs2/segment.c:2433:6: warning: variable 'err' set but not used [-Wunused-but-set-variable]
int err;
^
CC [M] fs/nilfs2/sufile.o
fs/nilfs2/sufile.c: In function 'nilfs_sufile_alloc':
fs/nilfs2/sufile.c:320:27: warning: variable 'ncleansegs' set but not used [-Wunused-but-set-variable]
unsigned long nsegments, ncleansegs, nsus, cnt;
^
CC [M] fs/nilfs2/alloc.o
fs/nilfs2/alloc.c: In function 'nilfs_palloc_prepare_alloc_entry':
fs/nilfs2/alloc.c:478:38: warning: variable 'groups_per_desc_block' set but not used [-Wunused-but-set-variable]
unsigned long n, entries_per_group, groups_per_desc_block;
^
Ryusuke Konishi [Sat, 7 Nov 2015 00:32:11 +0000 (16:32 -0800)]
MAINTAINERS: nilfs2: add header file for tracing
This adds header file "include/trace/events/nilfs2.h" to maintainer-ship
of nilfs2 so that updates to the nilfs2 header file go to the mailing list
of nilfs2.
Hitoshi Mitake [Sat, 7 Nov 2015 00:32:08 +0000 (16:32 -0800)]
nilfs2: add tracepoints for analyzing reading and writing metadata files
This patch adds tracepoints for analyzing requests of reading and writing
metadata files. The tracepoints cover every in-place mdt files (cpfile,
sufile, and datfile).
Hitoshi Mitake [Sat, 7 Nov 2015 00:32:05 +0000 (16:32 -0800)]
nilfs2: add tracepoints for analyzing sufile manipulation
This patch adds tracepoints which would be useful for analyzing segment
usage from a perspective of high level sufile manipulation (check, alloc,
free). sufile is an important in-place updated metadata file, so
analyzing the behavior would be useful for performance turning.
Hitoshi Mitake [Sat, 7 Nov 2015 00:32:02 +0000 (16:32 -0800)]
nilfs2: add a tracepoint for transaction events
This patch adds a tracepoint for transaction events of nilfs. With the
tracepoint, these events can be tracked: begin, abort, commit, trylock,
lock, and unlock. Basically, these events have corresponding functions
e.g. begin event corresponds nilfs_transaction_begin(). The unlock event
is an exception. It corresponds to the iteration in
nilfs_transaction_lock().
Only one tracepoint is introcued: nilfs2_transaction_transition. The
above events are distinguished with newly introduced enum. With this
tracepoint, we can analyse a critical section of segment constructoin.
Sample output by tpoint of perf-tools:
cp-4457 [000] ...1 63.266220: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800bf5ccc58 count = 1 flags = 9 state = BEGIN
cp-4457 [000] ...1 63.266221: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800bf5ccc58 count = 0 flags = 9 state = COMMIT
cp-4457 [000] ...1 63.266221: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800bf5ccc58 count = 0 flags = 9 state = COMMIT
segctord-4371 [001] ...1 68.261196: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800b889bdf8 count = 0 flags = 10 state = TRYLOCK
segctord-4371 [001] ...1 68.261280: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800b889bdf8 count = 0 flags = 10 state = LOCK
segctord-4371 [001] ...1 68.261877: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800b889bdf8 count = 1 flags = 10 state = BEGIN
segctord-4371 [001] ...1 68.262116: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800b889bdf8 count = 0 flags = 18 state = COMMIT
segctord-4371 [001] ...1 68.265032: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800b889bdf8 count = 0 flags = 18 state = UNLOCK
segctord-4371 [001] ...1 132.376847: nilfs2_transaction_transition: sb = ffff8802112b8800 ti = ffff8800b889bdf8 count = 0 flags = 10 state = TRYLOCK
This patch also does trivial cleaning of comma usage in collection stage
transition event for consistent coding style.
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hitoshi Mitake [Sat, 7 Nov 2015 00:31:59 +0000 (16:31 -0800)]
nilfs2: add a tracepoint for tracking stage transition of segment construction
This patch adds a tracepoint for tracking stage transition of block
collection in segment construction. With the tracepoint, we can analysis
the behavior of segment construction in depth. It would be useful for
bottleneck detection and debugging, etc.
The tracepoint is created with the standard trace API of linux (like ext3,
ext4, f2fs and btrfs). So we can analysis with existing tools easily. Of
course, more detailed analysis will be possible if we can create nilfs
specific analysis tools.
Below is an example of event dump with Brendan Gregg's perf-tools
(https://github.com/brendangregg/perf-tools). Time consumption between
each stage can be obtained.
For capturing transition correctly, this patch adds wrappers for the
member scnt of nilfs_cstage. With this change, every transition of the
stage can produce trace event in a correct manner.
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Ryusuke Konishi [Sat, 7 Nov 2015 00:31:56 +0000 (16:31 -0800)]
nilfs2: free unused dat file blocks during garbage collection
As a nilfs2 volume ages, the amount of available disk space decreases
little by little due to bloat of DAT (disk address translation) metadata
file. Even if we delete all files in a file system and free their block
addresses from the DAT file through a garbage collection, empty DAT blocks
are not freed.
This fixes the issue by extending the deallocator of block addresses so
that empty data blocks and empty bitmap blocks of DAT are deleted.
The following comparison shows the effect of this patch. Each shows disk
amount information of a nilfs2 volume that we cleaned out by deleting all
files and running gc after having filled 90% of its capacity.
Before:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 5001052123022844472072192 1% /test
After:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 500105212 16380 475078656 1% /test
Ryusuke Konishi [Sat, 7 Nov 2015 00:31:54 +0000 (16:31 -0800)]
nilfs2: add helper functions to delete blocks from dat file
This adds delete functions for data blocks of metadata files using bitmap
based allocator. nilfs_palloc_delete_entry_block() deletes an entry block
(e.g. block storing dat entries), and nilfs_palloc_delete_bitmap_block()
deletes a bitmap block, respectively.
These helpers are intended to be used in the successive change on
deallocator of block addresses ("nilfs2: free unused dat file blocks
during garbage collection").
Ryusuke Konishi [Sat, 7 Nov 2015 00:31:51 +0000 (16:31 -0800)]
nilfs2: get rid of nilfs_palloc_group_is_in()
This unfolds nilfs_palloc_group_is_in() helper function into
nilfs_palloc_freev() function to simplify a range check and an index
calculation repeatedy performed in a loop of the function.
The current implementation of nilfs_palloc_find_available_slot() function
is overkill. The underlying bit search routine is well optimized, so this
uses it more simply in nilfs_palloc_find_available_slot().
Ryusuke Konishi [Sat, 7 Nov 2015 00:31:45 +0000 (16:31 -0800)]
nilfs2: do not call nilfs_mdt_bgl_lock() needlessly
In the bitmap based allocator implementation, nilfs_mdt_bgl_lock() helper
is frequently used to get a spinlock protecting a target block group.
This reduces its usage and simplifies arguments of some related functions
by directly passing a pointer to the spinlock.
Ryusuke Konishi [Sat, 7 Nov 2015 00:31:43 +0000 (16:31 -0800)]
nilfs2: use nilfs_warning() in allocator implementation
This uses nilfs_warning() to replace "printk(KERN_WARNING ...);" in the
bitmap based allocator implementation of nilfs2. The warning messages are
modified to include the device name and the inode number in each message.
This makes it clear which metadata file of which device has output
warnings such as "entry number xxxx already freed".
Joe Perches [Sat, 7 Nov 2015 00:31:34 +0000 (16:31 -0800)]
checkpatch: improve tests for fixes:, long lines and stack dumps in commit log
Including BUG and stack dumps in commit logs makes checkpatch produce some
false positive warning messages.
checkpatch has multiple types of false positives:
o Commit message lines > 75 chars
o Stack dump address are mistaken for git commit IDs
o Link: and Fixes: lines are allowed to be > 75 chars.
o Fixes: style doesn't require ("<commit_description>")
parentheses and double quotes like other uses of
git commit ID and description.
Fix these.
Miscellanea:
o Move the test for checking $commit_log_possible_stack_dump
above the test for a long line commit message
o Add test for hex address surrounded by square or angle brackets
Signed-off-by: Joe Perches <joe@perches.com> Reported-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy Shevchenko [Sat, 7 Nov 2015 00:31:31 +0000 (16:31 -0800)]
lib/hexdump.c: truncate output in case of overflow
There is a classical off-by-one error in case when we try to place, for
example, 1+1 bytes as hex in the buffer of size 6. The expected result is
to get an output truncated, but in the reality we get 6 bytes filed
followed by terminating NUL.
Change the logic how we fill the output in case of byte dumping into
limited space. This will follow the snprintf() behaviour by truncating
output even on half bytes.
Fixes: 114fc1afb2de (hexdump: make it return number of bytes placed in buffer) Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reported-by: Aaro Koskinen <aaro.koskinen@nokia.com> Tested-by: Aaro Koskinen <aaro.koskinen@nokia.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cody P Schafer [Sat, 7 Nov 2015 00:31:28 +0000 (16:31 -0800)]
rbtree: clarify documentation of rbtree_postorder_for_each_entry_safe()
I noticed that commit a20135ffbc44 ("writeback: don't drain
bdi_writeback_congested on bdi destruction") added a usage of
rbtree_postorder_for_each_entry_safe() in mm/backing-dev.c which appears
to try to rb_erase() elements from an rbtree while iterating over it using
rbtree_postorder_for_each_entry_safe().
Doing this will cause random nodes to be missed by the iteration because
rb_erase() may rebalance the tree, changing the ordering that we're trying
to iterate over.
The previous documentation for rbtree_postorder_for_each_entry_safe()
wasn't clear that this wasn't allowed, it was taken from the docs for
list_for_each_entry_safe(), where erasing isn't a problem due to
list_del() not reordering.
Explicitly warn developers about this potential pit-fall.
Note that I haven't fixed the actual issue that (it appears) the commit
referenced above introduced (not familiar enough with that code).
In general (and in this case), the patterns to follow are:
- switch to rb_first() + rb_erase(), don't use
rbtree_postorder_for_each_entry_safe().
- keep the postorder iteration and don't rb_erase() at all. Instead
just clear the fields of rb_node & cgwb_congested_tree as required by
other users of those structures.
[akpm@linux-foundation.org: tweak comments] Signed-off-by: Cody P Schafer <dev@codyps.com> Cc: John de la Garza <john@jjdev.com> Cc: Michel Lespinasse <walken@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/kobject.c: use kvasprintf_const for formatting ->name
Sometimes kobject_set_name_vargs is called with a format string conaining
no %, or a format string of precisely "%s", where the single vararg
happens to point to .rodata. kvasprintf_const detects these cases for us
and returns a copy of that pointer instead of duplicating the string, thus
saving some run-time memory. Otherwise, it falls back to kvasprintf. We
just need to always deallocate ->name using kfree_const.
Unfortunately, the dance we need to do to perform the '/' -> '!'
sanitization makes the resulting code rather ugly.
I instrumented kstrdup_const to provide some statistics on the memory
saved, and for me this gave an additional ~14KB after boot (306KB was
already saved; this patch bumped that to 320KB). I have
KMALLOC_SHIFT_LOW==3, and since 80% of the kvasprintf_const hits were
satisfied by an 8-byte allocation, the 14K would roughly be quadrupled
when KMALLOC_SHIFT_LOW==5. Whether these numbers are sufficient to
justify the ugliness I'll leave to others to decide.
This adds kvasprintf_const which tries to use kstrdup_const if possible:
If the format string contains no % characters, or if the format string is
exactly "%s", we delegate to kstrdup_const. Otherwise, we fall back to
kvasprintf.
Just as for kstrdup_const, the main motivation is to save memory by
reusing .rodata when possible.
The return value should be freed by kfree_const, just like for
kstrdup_const.
There is deliberately no kasprintf_const: In the vast majority of cases,
the format string argument is a literal, so one can determine statically
whether one could instead use kstrdup_const directly (which would also
require one to change all corresponding kfree calls to kfree_const).
Dmitry Vyukov [Sat, 7 Nov 2015 00:31:17 +0000 (16:31 -0800)]
lib/llist.c: fix data race in llist_del_first
llist_del_first reads entry->next, but it did not acquire visibility over
the entry node. As the result it can get a stale value of entry->next
(e.g. NULL or whatever garbage was there before the appending thread
wrote correct value). And then commit that value as llist head with
cmpxchg. That will corrupt llist.
Note there is a control-dependency between read of head->first and read of
entry->next, but it does not make the code correct. Kernel memory model
unambiguously says: "A load-load control dependency requires a full read
memory barrier".
Use smp_load_acquire to acquire visibility over the entry node.
The data race was found with KernelThreadSanitizer (KTSAN).
Add a couple of simple tests for string_get_size(). The last one will
hang the kernel without the 'lib/string_helpers.c: fix infinite loop in
string_get_size()' fix.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: James Bottomley <JBottomley@Odin.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Months back, this was discussed, see https://lkml.org/lkml/2015/1/18/289
The result was the 64-bit version being "likely fine", "valuable" and
"correct". The discussion fell asleep but since there are possible users,
let's add it.
Signed-off-by: Martin Kepplinger <martin.kepplinger@theobroma-systems.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: George Spelvin <linux@horizon.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Maxime Coquelin <maxime.coquelin@st.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It is often overlooked that sign_extend32(), despite its name, is safe to
use for 16 and 8 bit types as well. This should help prevent sign
extension being done manually some other way.
Signed-off-by: Martin Kepplinger <martin.kepplinger@theobroma-systems.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: George Spelvin <linux@horizon.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Maxime Coquelin <maxime.coquelin@st.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Joe Perches [Sat, 7 Nov 2015 00:30:52 +0000 (16:30 -0800)]
get_maintainer: add subsystem to reviewer output
Reviewer output currently does not include the subsystem
that matched. Add it.
Miscellanea:
o Add a get_subsystem_name routine to centralize this
Signed-off-by: Joe Perches <joe@perches.com> Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Cc: Lee Jones <lee.jones@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Brian Norris [Sat, 7 Nov 2015 00:30:46 +0000 (16:30 -0800)]
get_maintainer: add --no-foo options to --help
Many flag options are boolean and support both a positive and a negative
invocation from the command line. Some of these are even mentioned by
example (e.g., --nogit is mentioned as a default option), but they aren't
explicitly mentioned in the list of options. It happens that some of
these are pretty important, as they are default-on, and to turn them off,
you have to know about the --no-foo version.
Rather than clutter the whole help text with bracketed '--[no]foo', let's
just mention the general rule, a la 'man gcc'.
Signed-off-by: Brian Norris <computersforpeace@gmail.com> Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Brian Norris [Sat, 7 Nov 2015 00:30:41 +0000 (16:30 -0800)]
get_maintainer: add missing documentation for --git-blame-signatures
I really haven't used this option much myself, so feel free to improve on
the documentation for it. I just noticed it while inspecting this script
for undocumented features.
Signed-off-by: Brian Norris <computersforpeace@gmail.com> Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mathias Krause [Sat, 7 Nov 2015 00:30:38 +0000 (16:30 -0800)]
printk: prevent userland from spoofing kernel messages
The following statement of ABI/testing/dev-kmsg is not quite right:
It is not possible to inject messages from userspace with the
facility number LOG_KERN (0), to make sure that the origin of the
messages can always be reliably determined.
Userland actually can inject messages with a facility of 0 by abusing the
fact that the facility is stored in a u8 data type. By using a facility
which is a multiple of 256 the assignment of msg->facility in log_store()
implicitly truncates it to 0, i.e. LOG_KERN, allowing users of /dev/kmsg
to spoof kernel messages as shown below:
The following call...
# printf '<%d>Kernel panic - not syncing: beer empty\n' 0 >/dev/kmsg
...leads to the following log entry (dmesg -x | tail -n 1):
user :emerg : [ 66.137758] Kernel panic - not syncing: beer empty
However, this call...
# printf '<%d>Kernel panic - not syncing: beer empty\n' 0x800 >/dev/kmsg
...leads to the slightly different log entry (note the kernel facility):
kern :emerg : [ 74.177343] Kernel panic - not syncing: beer empty
Fix that by limiting the user provided facility to 8 bit right from the
beginning and catch the truncation early.
Fixes: 7ff9554bb578 ("printk: convert byte-buffer to variable-length...") Signed-off-by: Mathias Krause <minipli@googlemail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Petr Mladek <pmladek@suse.cz> Cc: Alex Elder <elder@linaro.org> Cc: Joe Perches <joe@perches.com> Cc: Kay Sievers <kay@vrfy.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This adds a simple module for testing the kernel's printf facilities.
Previously, some %p extensions have caused a wrong return value in case
the entire output didn't fit and/or been unusable in kasprintf(). This
should help catch such issues. Also, it should help ensure that changes
to the formatting algorithms don't break anything.
I'm not sure if we have a struct dentry or struct file lying around at
boot time or if we can fake one, but most %p extensions should be
testable, as should the ordinary number and string formatting.
The nature of vararg functions means we can't use a more conventional
table-driven approach.
For now, this is mostly a skeleton; contributions are very
welcome. Some tests are/will be slightly annoying to write, since the
expected output depends on stuff like CONFIG_*, sizeof(long), runtime
values etc.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Martin Kletzander <mkletzan@redhat.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
shows, nobody uses the # flag with %p. Should one try to do so, one
will be met with
warning: `#' flag used with `%p' gnu_printf format [-Wformat]
(POSIX and C99 both say "... For other conversion specifiers, the
behavior is undefined.". Obviously, the kernel can choose to define
the behaviour however it wants, but as long as gcc issues that
warning, users are unlikely to show up.)
Since default_width is effectively always 2*sizeof(void*), we can
simplify the prologue of pointer() and save a few instructions.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Martin Kletzander <mkletzan@redhat.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/vsprintf.c: also improve sanity check in bstr_printf()
Quoting from 2aa2f9e21e4e ("lib/vsprintf.c: improve sanity check in
vsnprintf()"):
On 64 bit, size may very well be huge even if bit 31 happens to be 0.
Somehow it doesn't feel right that one can pass a 5 GiB buffer but not a
3 GiB one. So cap at INT_MAX as was probably the intention all along.
This is also the made-up value passed by sprintf and vsprintf.
I should have seen this copy-pasted instance back then, but let's just
do it now.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Martin Kletzander <mkletzan@redhat.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/vsprintf.c: handle invalid format specifiers more robustly
If we meet any invalid or unsupported format specifier, 'handling' it by
just printing it as a literal string is not safe: Presumably the format
string and the arguments passed gcc's type checking, but that means
something like sprintf(buf, "%n %pd", &intvar, dentry) would end up
interpreting &intvar as a struct dentry*.
When the offending specifier was %n it used to be at the end of the format
string, but we can't rely on that always being the case. Also, gcc
doesn't complain about some more or less exotic qualifiers (or 'length
modifiers' in posix-speak) such as 'j' or 'q', but being unrecognized by
the kernel's printf implementation, they'd be interpreted as unknown
specifiers, and the rest of arguments would be interpreted wrongly.
So let's complain about anything we don't understand, not just %n, and
stop pretending that we'd be able to make sense of the rest of the
format/arguments. If the offending specifier is in a printk() call we
unfortunately only get a "BUG: recent printk recursion!", but at least
direct users of the sprintf family will be caught.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Martin Kletzander <mkletzan@redhat.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Move all pointer-formatting documentation to one place in the code and one
place in the documentation instead of keeping it in three places with
different level of completeness. Documentation/printk-formats.txt has
detailed information about each modifier, docstring above pointer() has
short descriptions of them (as that is the function dealing with %p) and
docstring above vsprintf() is removed as redundant. Both docstrings in
the code that were modified are updated with a reminder of updating the
documentation upon any further change.
[akpm@linux-foundation.org: fix comment] Signed-off-by: Martin Kletzander <mkletzan@redhat.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Oleg Nesterov [Sat, 7 Nov 2015 00:30:06 +0000 (16:30 -0800)]
proc: actually make proc_fd_permission() thread-friendly
The commit 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly")
fixed the access to /proc/self/fd from sub-threads, but introduced another
problem: a sub-thread can't access /proc/<tid>/fd/ or /proc/thread-self/fd
if generic_permission() fails.
Change proc_fd_permission() to check same_thread_group(pid_task(), current).
Fixes: 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly") Reported-by: "Jin, Yihua" <yihua.jin@intel.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy Shevchenko [Sat, 7 Nov 2015 00:30:03 +0000 (16:30 -0800)]
fs/proc/array.c: set overflow flag in case of error
For now in task_name() we ignore the return code of string_escape_str()
call. This is not good if buffer suddenly becomes not big enough. Do the
proper error handling there.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@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>
Let's try to be consistent about data type of page order.
[sfr@canb.auug.org.au: fix build (type of pageblock_order)]
[hughd@google.com: some configs end up with MAX_ORDER and pageblock_order having different types] Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The race is pure theoretical. I don't it's possible to trigger it in
practice. But who knows.
We can fix the race by changing how encode PageTail() and compound_head()
within struct page to be able to update them in one shot.
The patch introduces page->compound_head into third double word block in
front of compound_dtor and compound_order. Bit 0 encodes PageTail() and
the rest bits are pointer to head page if bit zero is set.
The patch moves page->pmd_huge_pte out of word, just in case if an
architecture defines pgtable_t into something what can have the bit 0
set.
hugetlb_cgroup uses page->lru.next in the second tail page to store
pointer struct hugetlb_cgroup. The patch switch it to use page->private
in the second tail page instead. The space is free since ->first_page is
removed from the union.
The patch also opens possibility to remove HUGETLB_CGROUP_MIN_ORDER
limitation, since there's now space in first tail page to store struct
hugetlb_cgroup pointer. But that's out of scope of the patch.
That means page->compound_head shares storage space with:
That's too long list to be absolutely sure, but looks like nobody uses
bit 0 of the word.
page->rcu_head.next guaranteed[1] to have bit 0 clean as long as we use
call_rcu(), call_rcu_bh(), call_rcu_sched(), or call_srcu(). But future
call_rcu_lazy() is not allowed as it makes use of the bit and we can
get false positive PageTail().
mm: pack compound_dtor and compound_order into one word in struct page
The patch halves space occupied by compound_dtor and compound_order in
struct page.
For compound_order, it's trivial long -> short conversion.
For get_compound_page_dtor(), we now use hardcoded table for destructor
lookup and store its index in the struct page instead of direct pointer
to destructor. It shouldn't be a big trouble to maintain the table: we
have only two destructor and NULL currently.
This patch free up one word in tail pages for reuse. This is preparation
for the next patch.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Each `struct size_class' contains `struct zs_size_stat': an array of
NR_ZS_STAT_TYPE `unsigned long'. For zsmalloc built with no
CONFIG_ZSMALLOC_STAT this results in a waste of `2 * sizeof(unsigned
long)' per-class.
The patch removes unneeded `struct zs_size_stat' members by redefining
NR_ZS_STAT_TYPE (max stat idx in array).
Since both NR_ZS_STAT_TYPE and zs_stat_type are compile time constants,
GCC can eliminate zs_stat_inc()/zs_stat_dec() calls that use zs_stat_type
larger than NR_ZS_STAT_TYPE: CLASS_ALMOST_EMPTY and CLASS_ALMOST_FULL at
the moment.
./scripts/bloat-o-meter mm/zsmalloc.o.old mm/zsmalloc.o.new
add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-39 (-39)
function old new delta
fix_fullness_group 97 94 -3
insert_zspage 100 86 -14
remove_zspage 141 119 -22
To summarize:
a) each class now uses less memory
b) we avoid a number of dec/inc stats (a minor optimization,
but still).
The gain will increase once we introduce additional stats.
zsmalloc: don't test shrinker_enabled in zs_shrinker_count()
We don't let user to disable shrinker in zsmalloc (once it's been
enabled), so no need to check ->shrinker_enabled in zs_shrinker_count(),
at the moment at least.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit c60369f01125 ("staging: zsmalloc: prevent mappping in interrupt
context") added in_interrupt() check to zs_map_object() and 'hardirq.h'
include; but in_interrupt() macro is defined in 'preempt.h' not in
'hardirq.h', so include it instead.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hui Zhu [Sat, 7 Nov 2015 00:29:26 +0000 (16:29 -0800)]
zsmalloc: fix obj_to_head use page_private(page) as value but not pointer
In obj_malloc():
if (!class->huge)
/* record handle in the header of allocated chunk */
link->handle = handle;
else
/* record handle in first_page->private */
set_page_private(first_page, handle);
In the hugepage we save handle to private directly.
But in obj_to_head():
if (class->huge) {
VM_BUG_ON(!is_first_page(page));
return *(unsigned long *)page_private(page);
} else
return *(unsigned long *)obj;
It is used as a pointer.
The reason why there is no problem until now is huge-class page is born
with ZS_FULL so it can't be migrated. However, we need this patch for
future work: "VM-aware zsmalloced page migration" to reduce external
fragmentation.
Signed-off-by: Hui Zhu <zhuhui@xiaomi.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make the return type of zpool_get_type const; the string belongs to the
zpool driver and should not be modified. Remove the redundant type field
in the struct zpool; it is private to zpool.c and isn't needed since
->driver->type can be used directly. Add comments indicating strings must
be null-terminated.
Signed-off-by: Dan Streetman <ddstreet@ieee.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Seth Jennings <sjennings@variantweb.net> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Dan Streetman [Sat, 7 Nov 2015 00:29:15 +0000 (16:29 -0800)]
zswap: use charp for zswap param strings
Instead of using a fixed-length string for the zswap params, use charp.
This simplifies the code and uses less memory, as most zswap param strings
will be less than the current maximum length.
Signed-off-by: Dan Streetman <ddstreet@ieee.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Seth Jennings <sjennings@variantweb.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zram: keep the exact overcommited value in mem_used_max
`mem_used_max' is designed to store the max amount of memory zram consumed
to store the data. However, it does not represent the actual
'overcommited' (max) value. The existing code goes to -ENOMEM
overcommited case before it updates `->stats.max_used_pages', which hides
the reason we went to -ENOMEM in the first place -- we actually used more
memory than `->limit_pages':
alloced_pages = zs_get_total_pages(meta->mem_pool);
if (zram->limit_pages && alloced_pages > zram->limit_pages) {
zs_free(meta->mem_pool, handle);
ret = -ENOMEM;
goto out;
}
update_used_max(zram, alloced_pages);
Which is misleading. User will see -ENOMEM, check `->limit_pages', check
`->stats.max_used_pages', which will keep the value BEFORE zram passed
`->limit_pages', and see:
`->stats.max_used_pages' < `->limit_pages'
Move update_used_max() before we do `->limit_pages' check, so that
user will see:
`->stats.max_used_pages' > `->limit_pages'
should the overcommit and -ENOMEM happen.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When the user supplies an unsupported compression algorithm, keep the
previously selected one (knowingly supported) or the default one (if the
compression algorithm hasn't been changed yet).
Note that previously this operation (i.e. setting an invalid algorithm)
would result in no algorithm being selected, which means that this
represents a small change in the default behaviour.
Minchan said:
For initializing zram, we need to set up 3 optional parameters in advance.
1. the number of compression streams
2. memory limitation
3. compression algorithm
Although user pass completely wrong value to set up for 1 and 2
parameters, it's okay because they have default value so zram will be
initialized with the default value (of course, when user passes a wrong
value via *echo*, sysfs returns -EINVAL so the user can notice it).
But 3 is not consistent with other optional parameters. IOW, if the
user passes a wrong value to set up 3 parameter, zram's initialization
would fail unlike other optional parameters.
So this patch makes them consistent.
Signed-off-by: Luis Henriques <luis.henriques@canonical.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Jan Kara [Sat, 7 Nov 2015 00:28:55 +0000 (16:28 -0800)]
fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback
sync_file_range(2) is documented to issue writeback only for pages that
are not currently being written. After all the system call has been
created for userspace to be able to issue background writeout and so
waiting for in-flight IO is undesirable there. However commit ee53a891f474 ("mm: do_sync_mapping_range integrity fix") switched
do_sync_mapping_range() and thus sync_file_range() to issue writeback in
WB_SYNC_ALL mode since do_sync_mapping_range() was used by other code
relying on WB_SYNC_ALL semantics.
These days do_sync_mapping_range() went away and we can switch
sync_file_range(2) back to issuing WB_SYNC_NONE writeback. That should
help PostgreSQL avoid large latency spikes when flushing data in the
background.
Andres measured a 20% increase in transactions per second on an SSD disk.
Signed-off-by: Jan Kara <jack@suse.com> Reported-by: Andres Freund <andres@anarazel.de> Tested-By: Andres Freund <andres@anarazel.de> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Aaron Tomlin [Sat, 7 Nov 2015 00:28:52 +0000 (16:28 -0800)]
thp: remove unused vma parameter from khugepaged_alloc_page
The "vma" parameter to khugepaged_alloc_page() is unused. It has to
remain unused or the drop read lock 'map_sem' optimisation introduce by
commit 8b1645685acf ("mm, THP: don't hold mmap_sem in khugepaged when
allocating THP") wouldn't be safe. So let's remove it.
Michal Hocko [Sat, 7 Nov 2015 00:28:49 +0000 (16:28 -0800)]
mm, fs: introduce mapping_gfp_constraint()
There are many places which use mapping_gfp_mask to restrict a more
generic gfp mask which would be used for allocations which are not
directly related to the page cache but they are performed in the same
context.
Let's introduce a helper function which makes the restriction explicit and
easier to track. This patch doesn't introduce any functional changes.
[akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Michal Hocko <mhocko@suse.com> Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman [Sat, 7 Nov 2015 00:28:43 +0000 (16:28 -0800)]
mm: page_alloc: hide some GFP internals and document the bits and flag combinations
Andrew stated the following
We have quite a history of remote parts of the kernel using
weird/wrong/inexplicable combinations of __GFP_ flags. I tend
to think that this is because we didn't adequately explain the
interface.
And I don't think that gfp.h really improved much in this area as
a result of this patchset. Could you go through it some time and
decide if we've adequately documented all this stuff?
This patches first moves some GFP flag combinations that are part of the MM
internals to mm/internal.h. The rest of the patch documents the __GFP_FOO
bits under various headings and then documents the flag combinations. It
will not help callers that are brain damaged but the clarity might motivate
some fixes and avoid future mistakes.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman [Sat, 7 Nov 2015 00:28:40 +0000 (16:28 -0800)]
mm, page_alloc: only enforce watermarks for order-0 allocations
The primary purpose of watermarks is to ensure that reclaim can always
make forward progress in PF_MEMALLOC context (kswapd and direct reclaim).
These assume that order-0 allocations are all that is necessary for
forward progress.
High-order watermarks serve a different purpose. Kswapd had no high-order
awareness before they were introduced
(https://lkml.kernel.org/r/413AA7B2.4000907@yahoo.com.au). This was
particularly important when there were high-order atomic requests. The
watermarks both gave kswapd awareness and made a reserve for those atomic
requests.
There are two important side-effects of this. The most important is that
a non-atomic high-order request can fail even though free pages are
available and the order-0 watermarks are ok. The second is that
high-order watermark checks are expensive as the free list counts up to
the requested order must be examined.
With the introduction of MIGRATE_HIGHATOMIC it is no longer necessary to
have high-order watermarks. Kswapd and compaction still need high-order
awareness which is handled by checking that at least one suitable
high-order page is free.
With the patch applied, there was little difference in the allocation
failure rates as the atomic reserves are small relative to the number of
allocation attempts. The expected impact is that there will never be an
allocation failure report that shows suitable pages on the free lists.
The one potential side-effect of this is that in a vanilla kernel, the
watermark checks may have kept a free page for an atomic allocation. Now,
we are 100% relying on the HighAtomic reserves and an early allocation to
have allocated them. If the first high-order atomic allocation is after
the system is already heavily fragmented then it'll fail.
[akpm@linux-foundation.org: simplify __zone_watermark_ok(), per Vlastimil] Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman [Sat, 7 Nov 2015 00:28:37 +0000 (16:28 -0800)]
mm, page_alloc: reserve pageblocks for high-order atomic allocations on demand
High-order watermark checking exists for two reasons -- kswapd high-order
awareness and protection for high-order atomic requests. Historically the
kernel depended on MIGRATE_RESERVE to preserve min_free_kbytes as
high-order free pages for as long as possible. This patch introduces
MIGRATE_HIGHATOMIC that reserves pageblocks for high-order atomic
allocations on demand and avoids using those blocks for order-0
allocations. This is more flexible and reliable than MIGRATE_RESERVE was.
A MIGRATE_HIGHORDER pageblock is created when an atomic high-order
allocation request steals a pageblock but limits the total number to 1% of
the zone. Callers that speculatively abuse atomic allocations for
long-lived high-order allocations to access the reserve will quickly fail.
Note that SLUB is currently not such an abuser as it reclaims at least
once. It is possible that the pageblock stolen has few suitable
high-order pages and will need to steal again in the near future but there
would need to be strong justification to search all pageblocks for an
ideal candidate.
The pageblocks are unreserved if an allocation fails after a direct
reclaim attempt.
The watermark checks account for the reserved pageblocks when the
allocation request is not a high-order atomic allocation.
The reserved pageblocks can not be used for order-0 allocations. This may
allow temporary wastage until a failed reclaim reassigns the pageblock.
This is deliberate as the intent of the reservation is to satisfy a
limited number of atomic high-order short-lived requests if the system
requires them.
The stutter benchmark was used to evaluate this but while it was running
there was a systemtap script that randomly allocated between 1 high-order
page and 12.5% of memory's worth of order-3 pages using GFP_ATOMIC. This
is much larger than the potential reserve and it does not attempt to be
realistic. It is intended to stress random high-order allocations from an
unknown source, show that there is a reduction in failures without
introducing an anomaly where atomic allocations are more reliable than
regular allocations. The amount of memory reserved varied throughout the
workload as reserves were created and reclaimed under memory pressure.
The allocation failures once the workload warmed up were as follows;
4.2-rc5-vanilla 70%
4.2-rc5-atomic-reserve 56%
The failure rate was also measured while building multiple kernels. The
failure rate was 14% but is 6% with this patch applied.
Overall, this is a small reduction but the reserves are small relative to
the number of allocation requests. In early versions of the patch, the
failure rate reduced by a much larger amount but that required much larger
reserves and perversely made atomic allocations seem more reliable than
regular allocations.
[yalin.wang2010@gmail.com: fix redundant check and a memory leak] Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: yalin wang <yalin.wang2010@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman [Sat, 7 Nov 2015 00:28:34 +0000 (16:28 -0800)]
mm, page_alloc: remove MIGRATE_RESERVE
MIGRATE_RESERVE preserves an old property of the buddy allocator that
existed prior to fragmentation avoidance -- min_free_kbytes worth of pages
tended to remain contiguous until the only alternative was to fail the
allocation. At the time it was discovered that high-order atomic
allocations relied on this property so MIGRATE_RESERVE was introduced. A
later patch will introduce an alternative MIGRATE_HIGHATOMIC so this patch
deletes MIGRATE_RESERVE and supporting code so it'll be easier to review.
Note that this patch in isolation may look like a false regression if
someone was bisecting high-order atomic allocation failures.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman [Sat, 7 Nov 2015 00:28:31 +0000 (16:28 -0800)]
mm, page_alloc: delete the zonelist_cache
The zonelist cache (zlc) was introduced to skip over zones that were
recently known to be full. This avoided expensive operations such as the
cpuset checks, watermark calculations and zone_reclaim. The situation
today is different and the complexity of zlc is harder to justify.
1) The cpuset checks are no-ops unless a cpuset is active and in general
are a lot cheaper.
2) zone_reclaim is now disabled by default and I suspect that was a large
source of the cost that zlc wanted to avoid. When it is enabled, it's
known to be a major source of stalling when nodes fill up and it's
unwise to hit every other user with the overhead.
3) Watermark checks are expensive to calculate for high-order
allocation requests. Later patches in this series will reduce the cost
of the watermark checking.
4) The most important issue is that in the current implementation it
is possible for a failed THP allocation to mark a zone full for order-0
allocations and cause a fallback to remote nodes.
The last issue could be addressed with additional complexity but as the
benefit of zlc is questionable, it is better to remove it. If stalls due
to zone_reclaim are ever reported then an alternative would be to
introduce deferring logic based on a timeout inside zone_reclaim itself
and leave the page allocator fast paths alone.
The impact on page-allocator microbenchmarks is negligible as they don't
hit the paths where the zlc comes into play. Most page-reclaim related
workloads showed no noticeable difference as a result of the removal.
The impact was noticeable in a workload called "stutter". One part uses a
lot of anonymous memory, a second measures mmap latency and a third copies
a large file. In an ideal world the latency application would not notice
the mmap latency. On a 2-node machine the results of this patch are
Note that the maximum stall latency went from 24 seconds to 12 which is
still bad but an improvement. The milage varies considerably 2-node
machine on an earlier test went from 494 seconds to 47 seconds and a
4-node machine that tested an earlier version of this patch went from a
worst case stall time of 6 seconds to 67ms. The nature of the benchmark
is inherently unpredictable as it is hammering the system and the milage
will vary between machines.
There is a secondary impact with potentially more direct reclaim because
zones are now being considered instead of being skipped by zlc. In this
particular test run it did not occur so will not be described. However,
in at least one test the following was observed
1. Direct reclaim rates were higher. This was likely due to direct reclaim
being entered instead of the zlc disabling a zone and busy looping.
Busy looping may have the effect of allowing kswapd to make more
progress and in some cases may be better overall. If this is found then
the correct action is to put direct reclaimers to sleep on a waitqueue
and allow kswapd make forward progress. Busy looping on the zlc is even
worse than when the allocator used to blindly call congestion_wait().
2. There was higher swap activity as direct reclaim was active.
3. Direct reclaim efficiency was lower. This is related to 1 as more
scanning activity also encountered more pages that could not be
immediately reclaimed
In that case, the direct page scan and reclaim rates are noticeable but
it is not considered a problem for a few reasons
1. The test is primarily concerned with latency. The mmap attempts are also
faulted which means there are THP allocation requests. The ZLC could
cause zones to be disabled causing the process to busy loop instead
of reclaiming. This looks like elevated direct reclaim activity but
it's the correct action to take based on what processes requested.
2. The test hammers reclaim and compaction heavily. The number of successful
THP faults is highly variable but affects the reclaim stats. It's not a
realistic or reasonable measure of page reclaim activity.
3. No other page-reclaim intensive workload that was tested showed a problem.
4. If a workload is identified that benefitted from the busy looping then it
should be fixed by having direct reclaimers sleep on a wait queue until
woken by kswapd instead of busy looping. We had this class of problem before
when congestion_waits() with a fixed timeout was a brain damaged decision
but happened to benefit some workloads.
If a workload is identified that relied on the zlc to busy loop then it
should be fixed correctly and have a direct reclaimer sleep on a waitqueue
until woken by kswapd.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Christoph Lameter <cl@linux.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mel Gorman [Sat, 7 Nov 2015 00:28:28 +0000 (16:28 -0800)]
mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM
__GFP_WAIT was used to signal that the caller was in atomic context and
could not sleep. Now it is possible to distinguish between true atomic
context and callers that are not willing to sleep. The latter should
clear __GFP_DIRECT_RECLAIM so kswapd will still wake. As clearing
__GFP_WAIT behaves differently, there is a risk that people will clear the
wrong flags. This patch renames __GFP_WAIT to __GFP_RECLAIM to clearly
indicate what it does -- setting it allows all reclaim activity, clearing
them prevents it.
[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
projects / mirror_ubuntu-eoan-kernel.git / log