Skip to content

K
Kernel

openeuler / Kernel
接近 2 年 前同步成功

通知 8
Star 0
Fork 0
K
Kernel
切换分支/标签
  1. 19 10月, 2017 1 次提交
    • D
      mm, percpu: add support for __GFP_NOWARN flag · 0ea7eeec
      由 Daniel Borkmann 提交于 
      Add an option for pcpu_alloc() to support __GFP_NOWARN flag.
Currently, we always throw a warning when size or alignment
is unsupported (and also dump stack on failed allocation
requests). The warning itself is harmless since we return
NULL anyway for any failed request, which callers are
required to handle anyway. However, it becomes harmful when
panic_on_warn is set.

The rationale for the WARN() in pcpu_alloc() is that it can
be tracked when larger than supported allocation requests are
made such that allocations limits can be tweaked if warranted.
This makes sense for in-kernel users, however, there are users
of pcpu allocator where allocation size is derived from user
space requests, e.g. when creating BPF maps. In these cases,
the requests should fail gracefully without throwing a splat.

The current work-around was to check allocation size against
the upper limit of PCPU_MIN_UNIT_SIZE from call-sites for
bailing out prior to a call to pcpu_alloc() in order to
avoid throwing the WARN(). This is bad in multiple ways since
PCPU_MIN_UNIT_SIZE is an implementation detail, and having
the checks on call-sites only complicates the code for no
good reason. Thus, lets fix it generically by supporting the
__GFP_NOWARN flag that users can then use with calling the
__alloc_percpu_gfp() helper instead.
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      0ea7eeec
  3. 14 10月, 2017 8 次提交
  5. 10 10月, 2017 1 次提交
  7. 04 10月, 2017 19 次提交
  9. 28 9月, 2017 2 次提交
    • D
      percpu: fix iteration to prevent skipping over block · 1fa4df3e
      由 Dennis Zhou 提交于 
      The iterator functions pcpu_next_md_free_region and
pcpu_next_fit_region use the block offset to determine if they have
checked the area in the prior iteration. However, this causes an issue
when the block offset is greater than subsequent block contig hints. If
within the iterator it moves to check subsequent blocks, it may fail in
the second predicate due to the block offset not being cleared. Thus,
this causes the allocator to skip over blocks leading to false failures
when allocating from the reserved chunk. While this happens in the
general case as well, it will only fail if it cannot allocate a new
chunk.

This patch resets the block offset to 0 to pass the second predicate
when checking subseqent blocks within the iterator function.
Signed-off-by: NDennis Zhou <dennisszhou@gmail.com>
Reported-and-tested-by: NLuis Henriques <lhenriques@suse.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
      1fa4df3e
    • D
      percpu: fix starting offset for chunk statistics traversal · 2e08d20d
      由 Dennis Zhou 提交于 
      This patch fixes the starting offset used when scanning chunks to
compute the chunk statistics. The value start_offset (and end_offset)
are managed in bytes while the traversal occurs over bits. Thus for the
reserved and dynamic chunk, it may incorrectly skip over the initial
allocations.
Signed-off-by: NDennis Zhou <dennisszhou@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
      2e08d20d
  11. 25 9月, 2017 1 次提交
    • L
      fs: Fix page cache inconsistency when mixing buffered and AIO DIO · 332391a9
      由 Lukas Czerner 提交于 
      Currently when mixing buffered reads and asynchronous direct writes it
is possible to end up with the situation where we have stale data in the
page cache while the new data is already written to disk. This is
permanent until the affected pages are flushed away. Despite the fact
that mixing buffered and direct IO is ill-advised it does pose a thread
for a data integrity, is unexpected and should be fixed.

Fix this by deferring completion of asynchronous direct writes to a
process context in the case that there are mapped pages to be found in
the inode. Later before the completion in dio_complete() invalidate
the pages in question. This ensures that after the completion the pages
in the written area are either unmapped, or populated with up-to-date
data. Also do the same for the iomap case which uses
iomap_dio_complete() instead.

This has a side effect of deferring the completion to a process context
for every AIO DIO that happens on inode that has pages mapped. However
since the consensus is that this is ill-advised practice the performance
implication should not be a problem.

This was based on proposal from Jeff Moyer, thanks!
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      332391a9
  13. 15 9月, 2017 1 次提交
    • T
      sched/wait: Introduce wakeup boomark in wake_up_page_bit · 11a19c7b
      由 Tim Chen 提交于 
      Now that we have added breaks in the wait queue scan and allow bookmark
on scan position, we put this logic in the wake_up_page_bit function.

We can have very long page wait list in large system where multiple
pages share the same wait list. We break the wake up walk here to allow
other cpus a chance to access the list, and not to disable the interrupts
when traversing the list for too long.  This reduces the interrupt and
rescheduling latency, and excessive page wait queue lock hold time.

[ v2: Remove bookmark_wake_function ]
Signed-off-by: NTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      11a19c7b
  15. 14 9月, 2017 2 次提交
    • P
      mm, page_owner: skip unnecessary stack_trace entries · 5f48f0bd
      由 Prakash Gupta 提交于 
      The page_owner stacktrace always begin as follows:

  [<ffffff987bfd48f4>] save_stack+0x40/0xc8
  [<ffffff987bfd4da8>] __set_page_owner+0x3c/0x6c

These two entries do not provide any useful information and limits the
available stacktrace depth.  The page_owner stacktrace was skipping
caller function from stack entries but this was missed with commit
f2ca0b55 ("mm/page_owner: use stackdepot to store stacktrace")

Example page_owner entry after the patch:

  Page allocated via order 0, mask 0x8(ffffff80085fb714)
  PFN 654411 type Movable Block 639 type CMA Flags 0x0(ffffffbe5c7f12c0)
  [<ffffff9b64989c14>] post_alloc_hook+0x70/0x80
  ...
  [<ffffff9b651216e8>] msm_comm_try_state+0x5f8/0x14f4
  [<ffffff9b6512486c>] msm_vidc_open+0x5e4/0x7d0
  [<ffffff9b65113674>] msm_v4l2_open+0xa8/0x224

Link: http://lkml.kernel.org/r/1504078343-28754-2-git-send-email-guptap@codeaurora.org
Fixes: f2ca0b55 ("mm/page_owner: use stackdepot to store stacktrace")
Signed-off-by: NPrakash Gupta <guptap@codeaurora.org>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5f48f0bd
    • M
      mm: treewide: remove GFP_TEMPORARY allocation flag · 0ee931c4
      由 Michal Hocko 提交于 
      GFP_TEMPORARY was introduced by commit e12ba74d ("Group short-lived
and reclaimable kernel allocations") along with __GFP_RECLAIMABLE.  It's
primary motivation was to allow users to tell that an allocation is
short lived and so the allocator can try to place such allocations close
together and prevent long term fragmentation.  As much as this sounds
like a reasonable semantic it becomes much less clear when to use the
highlevel GFP_TEMPORARY allocation flag.  How long is temporary? Can the
context holding that memory sleep? Can it take locks? It seems there is
no good answer for those questions.

The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
__GFP_RECLAIMABLE which in itself is tricky because basically none of
the existing caller provide a way to reclaim the allocated memory.  So
this is rather misleading and hard to evaluate for any benefits.

I have checked some random users and none of them has added the flag
with a specific justification.  I suspect most of them just copied from
other existing users and others just thought it might be a good idea to
use without any measuring.  This suggests that GFP_TEMPORARY just
motivates for cargo cult usage without any reasoning.

I believe that our gfp flags are quite complex already and especially
those with highlevel semantic should be clearly defined to prevent from
confusion and abuse.  Therefore I propose dropping GFP_TEMPORARY and
replace all existing users to simply use GFP_KERNEL.  Please note that
SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
so they will be placed properly for memory fragmentation prevention.

I can see reasons we might want some gfp flag to reflect shorterm
allocations but I propose starting from a clear semantic definition and
only then add users with proper justification.

This was been brought up before LSF this year by Matthew [1] and it
turned out that GFP_TEMPORARY really doesn't have a clear semantic.  It
seems to be a heuristic without any measured advantage for most (if not
all) its current users.  The follow up discussion has revealed that
opinions on what might be temporary allocation differ a lot between
developers.  So rather than trying to tweak existing users into a
semantic which they haven't expected I propose to simply remove the flag
and start from scratch if we really need a semantic for short term
allocations.

[1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org

[akpm@linux-foundation.org: fix typo]
[akpm@linux-foundation.org: coding-style fixes]
[sfr@canb.auug.org.au: drm/i915: fix up]
  Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Acked-by: NMel Gorman <mgorman@suse.de>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      0ee931c4
  17. 12 9月, 2017 1 次提交
  19. 09 9月, 2017 4 次提交