linux-toradex.git/mm/page-writeback.c, branch v5.8-rc4

mm/page-writeback: fix a typo in comment "effictive"->"effective"

2020-06-05T02:06:24+00:00

There is a typo in comment, fix it.

Signed-off-by: Ethon Paul 
Signed-off-by: Andrew Morton 
Link: http://lkml.kernel.org/r/20200411003513.14613-1-ethp@qq.com
Signed-off-by: Linus Torvalds

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

2020-06-03T23:27:18+00:00

Pull networking updates from David Miller:

 1) Allow setting bluetooth L2CAP modes via socket option, from Luiz
    Augusto von Dentz.

 2) Add GSO partial support to igc, from Sasha Neftin.

 3) Several cleanups and improvements to r8169 from Heiner Kallweit.

 4) Add IF_OPER_TESTING link state and use it when ethtool triggers a
    device self-test. From Andrew Lunn.

 5) Start moving away from custom driver versions, use the globally
    defined kernel version instead, from Leon Romanovsky.

 6) Support GRO vis gro_cells in DSA layer, from Alexander Lobakin.

 7) Allow hard IRQ deferral during NAPI, from Eric Dumazet.

 8) Add sriov and vf support to hinic, from Luo bin.

 9) Support Media Redundancy Protocol (MRP) in the bridging code, from
    Horatiu Vultur.

10) Support netmap in the nft_nat code, from Pablo Neira Ayuso.

11) Allow UDPv6 encapsulation of ESP in the ipsec code, from Sabrina
    Dubroca. Also add ipv6 support for espintcp.

12) Lots of ReST conversions of the networking documentation, from Mauro
    Carvalho Chehab.

13) Support configuration of ethtool rxnfc flows in bcmgenet driver,
    from Doug Berger.

14) Allow to dump cgroup id and filter by it in inet_diag code, from
    Dmitry Yakunin.

15) Add infrastructure to export netlink attribute policies to
    userspace, from Johannes Berg.

16) Several optimizations to sch_fq scheduler, from Eric Dumazet.

17) Fallback to the default qdisc if qdisc init fails because otherwise
    a packet scheduler init failure will make a device inoperative. From
    Jesper Dangaard Brouer.

18) Several RISCV bpf jit optimizations, from Luke Nelson.

19) Correct the return type of the ->ndo_start_xmit() method in several
    drivers, it's netdev_tx_t but many drivers were using
    'int'. From Yunjian Wang.

20) Add an ethtool interface for PHY master/slave config, from Oleksij
    Rempel.

21) Add BPF iterators, from Yonghang Song.

22) Add cable test infrastructure, including ethool interfaces, from
    Andrew Lunn. Marvell PHY driver is the first to support this
    facility.

23) Remove zero-length arrays all over, from Gustavo A. R. Silva.

24) Calculate and maintain an explicit frame size in XDP, from Jesper
    Dangaard Brouer.

25) Add CAP_BPF, from Alexei Starovoitov.

26) Support terse dumps in the packet scheduler, from Vlad Buslov.

27) Support XDP_TX bulking in dpaa2 driver, from Ioana Ciornei.

28) Add devm_register_netdev(), from Bartosz Golaszewski.

29) Minimize qdisc resets, from Cong Wang.

30) Get rid of kernel_getsockopt and kernel_setsockopt in order to
    eliminate set_fs/get_fs calls. From Christoph Hellwig.

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2517 commits)
  selftests: net: ip_defrag: ignore EPERM
  net_failover: fixed rollback in net_failover_open()
  Revert "tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv"
  Revert "tipc: Fix potential tipc_node refcnt leak in tipc_rcv"
  vmxnet3: allow rx flow hash ops only when rss is enabled
  hinic: add set_channels ethtool_ops support
  selftests/bpf: Add a default $(CXX) value
  tools/bpf: Don't use $(COMPILE.c)
  bpf, selftests: Use bpf_probe_read_kernel
  s390/bpf: Use bcr 0,%0 as tail call nop filler
  s390/bpf: Maintain 8-byte stack alignment
  selftests/bpf: Fix verifier test
  selftests/bpf: Fix sample_cnt shared between two threads
  bpf, selftests: Adapt cls_redirect to call csum_level helper
  bpf: Add csum_level helper for fixing up csum levels
  bpf: Fix up bpf_skb_adjust_room helper's skb csum setting
  sfc: add missing annotation for efx_ef10_try_update_nic_stats_vf()
  crypto/chtls: IPv6 support for inline TLS
  Crypto/chcr: Fixes a coccinile check error
  Crypto/chcr: Fixes compilations warnings
  ...

mm/writeback: discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead

2020-06-02T17:59:08+00:00

After an NFS page has been written it is considered "unstable" until a
COMMIT request succeeds.  If the COMMIT fails, the page will be
re-written.

These "unstable" pages are currently accounted as "reclaimable", either
in WB_RECLAIMABLE, or in NR_UNSTABLE_NFS which is included in a
'reclaimable' count.  This might have made sense when sending the COMMIT
required a separate action by the VFS/MM (e.g.  releasepage() used to
send a COMMIT).  However now that all writes generated by ->writepages()
will automatically be followed by a COMMIT (since commit 919e3bd9a875
("NFS: Ensure we commit after writeback is complete")) it makes more
sense to treat them as writeback pages.

So this patch removes NR_UNSTABLE_NFS and accounts unstable pages in
NR_WRITEBACK and WB_WRITEBACK.

A particular effect of this change is that when
wb_check_background_flush() calls wb_over_bg_threshold(), the latter
will report 'true' a lot less often as the 'unstable' pages are no
longer considered 'dirty' (as there is nothing that writeback can do
about them anyway).

Currently wb_check_background_flush() will trigger writeback to NFS even
when there are relatively few dirty pages (if there are lots of unstable
pages), this can result in small writes going to the server (10s of
Kilobytes rather than a Megabyte) which hurts throughput.  With this
patch, there are fewer writes which are each larger on average.

Where the NR_UNSTABLE_NFS count was included in statistics
virtual-files, the entry is retained, but the value is hard-coded as
zero.  static trace points and warning printks which mentioned this
counter no longer report it.

[akpm@linux-foundation.org: re-layout comment]
[akpm@linux-foundation.org: fix printk warning]
Signed-off-by: NeilBrown 
Signed-off-by: Andrew Morton 
Reviewed-by: Jan Kara 
Reviewed-by: Christoph Hellwig 
Acked-by: Trond Myklebust 
Acked-by: Michal Hocko 	[mm]
Cc: Christoph Hellwig 
Cc: Chuck Lever 
Link: http://lkml.kernel.org/r/87d06j7gqa.fsf@notabene.neil.brown.name
Signed-off-by: Linus Torvalds

mm/writeback: replace PF_LESS_THROTTLE with PF_LOCAL_THROTTLE

2020-06-02T17:59:08+00:00

PF_LESS_THROTTLE exists for loop-back nfsd (and a similar need in the
loop block driver and callers of prctl(PR_SET_IO_FLUSHER)), where a
daemon needs to write to one bdi (the final bdi) in order to free up
writes queued to another bdi (the client bdi).

The daemon sets PF_LESS_THROTTLE and gets a larger allowance of dirty
pages, so that it can still dirty pages after other processses have been
throttled.  The purpose of this is to avoid deadlock that happen when
the PF_LESS_THROTTLE process must write for any dirty pages to be freed,
but it is being thottled and cannot write.

This approach was designed when all threads were blocked equally,
independently on which device they were writing to, or how fast it was.
Since that time the writeback algorithm has changed substantially with
different threads getting different allowances based on non-trivial
heuristics.  This means the simple "add 25%" heuristic is no longer
reliable.

The important issue is not that the daemon needs a *larger* dirty page
allowance, but that it needs a *private* dirty page allowance, so that
dirty pages for the "client" bdi that it is helping to clear (the bdi
for an NFS filesystem or loop block device etc) do not affect the
throttling of the daemon writing to the "final" bdi.

This patch changes the heuristic so that the task is not throttled when
the bdi it is writing to has a dirty page count below below (or equal
to) the free-run threshold for that bdi.  This ensures it will always be
able to have some pages in flight, and so will not deadlock.

In a steady-state, it is expected that PF_LOCAL_THROTTLE tasks might
still be throttled by global threshold, but that is acceptable as it is
only the deadlock state that is interesting for this flag.

This approach of "only throttle when target bdi is busy" is consistent
with the other use of PF_LESS_THROTTLE in current_may_throttle(), were
it causes attention to be focussed only on the target bdi.

So this patch
 - renames PF_LESS_THROTTLE to PF_LOCAL_THROTTLE,
 - removes the 25% bonus that that flag gives, and
 - If PF_LOCAL_THROTTLE is set, don't delay at all unless the
   global and the local free-run thresholds are exceeded.

Note that previously realtime threads were treated the same as
PF_LESS_THROTTLE threads.  This patch does *not* change the behvaiour
for real-time threads, so it is now different from the behaviour of nfsd
and loop tasks.  I don't know what is wanted for realtime.

[akpm@linux-foundation.org: coding style fixes]
Signed-off-by: NeilBrown 
Signed-off-by: Andrew Morton 
Reviewed-by: Jan Kara 
Acked-by: Chuck Lever 	[nfsd]
Cc: Christoph Hellwig 
Cc: Michal Hocko 
Cc: Trond Myklebust 
Link: http://lkml.kernel.org/r/87ftbf7gs3.fsf@notabene.neil.brown.name
Signed-off-by: Linus Torvalds

mm/page-writeback.c: remove unused variable

2020-06-02T17:59:08+00:00

Commit 64081362e8ff ("mm/page-writeback.c: fix range_cyclic writeback
vs writepages deadlock") left unused variable, remove it.

Signed-off-by: Chao Yu 
Signed-off-by: Andrew Morton 
Reviewed-by: David Hildenbrand 
Link: http://lkml.kernel.org/r/20200528033740.17269-1-yuchao0@huawei.com
Signed-off-by: Linus Torvalds

sysctl: pass kernel pointers to ->proc_handler

2020-04-27T06:07:40+00:00

Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig 
Acked-by: Andrey Ignatov 
Signed-off-by: Al Viro

mm/gup/writeback: add callbacks for inaccessible pages

2020-04-02T16:35:27+00:00

With the introduction of protected KVM guests on s390 there is now a
concept of inaccessible pages.  These pages need to be made accessible
before the host can access them.

While cpu accesses will trigger a fault that can be resolved, I/O accesses
will just fail.  We need to add a callback into architecture code for
places that will do I/O, namely when writeback is started or when a page
reference is taken.

This is not only to enable paging, file backing etc, it is also necessary
to protect the host against a malicious user space.  For example a bad
QEMU could simply start direct I/O on such protected memory.  We do not
want userspace to be able to trigger I/O errors and thus the logic is
"whenever somebody accesses that page (gup) or does I/O, make sure that
this page can be accessed".  When the guest tries to access that page we
will wait in the page fault handler for writeback to have finished and for
the page_ref to be the expected value.

On s390x the function is not supposed to fail, so it is ok to use a
WARN_ON on failure.  If we ever need some more finegrained handling we can
tackle this when we know the details.

Signed-off-by: Claudio Imbrenda 
Signed-off-by: Andrew Morton 
Reviewed-by: David Hildenbrand 
Reviewed-by: Christian Borntraeger 
Reviewed-by: John Hubbard 
Acked-by: Will Deacon 
Cc: Jan Kara 
Cc: Matthew Wilcox 
Cc: Ira Weiny 
Cc: Jérôme Glisse 
Cc: Al Viro 
Cc: Christoph Hellwig 
Cc: Dan Williams 
Cc: Dave Chinner 
Cc: Jason Gunthorpe 
Cc: Jonathan Corbet 
Cc: Michal Hocko 
Cc: Mike Kravetz 
Cc: Shuah Khan 
Cc: Vlastimil Babka 
Link: http://lkml.kernel.org/r/20200306132537.783769-3-imbrenda@linux.ibm.com
Signed-off-by: Linus Torvalds

mm/page-writeback.c: use VM_BUG_ON_PAGE in clear_page_dirty_for_io

2020-04-02T16:35:26+00:00

Dumping the page information in this circumstance helps for debugging.

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Reviewed-by: Christoph Hellwig 
Acked-by: Kirill A. Shutemov 
Cc: Aneesh Kumar K.V 
Cc: Pankaj Gupta 
Link: http://lkml.kernel.org/r/20200318140253.6141-7-willy@infradead.org
Signed-off-by: Linus Torvalds

mm/page-writeback.c: write_cache_pages(): deduplicate identical checks

2020-04-02T16:35:26+00:00

There used to be a 'retry' label in between the two (identical) checks
when first introduced in commit f446daaea9d4 ("mm: implement writeback
livelock avoidance using page tagging"), and later modified/updated in
commit 6e6938b6d313 ("writeback: introduce .tagged_writepages for the
WB_SYNC_NONE sync stage").

The label has been removed in commit 64081362e8ff ("mm/page-writeback.c:
fix range_cyclic writeback vs writepages deadlock"), and the (identical)
checks are now present / performed immediately one after another.

So, remove/deduplicate the latter check, moving tag_pages_for_writeback()
into the former check before the 'tag' variable assignment, so it's clear
that it's not used in this (similarly-named) function call but only later
in pagevec_lookup_range_tag().

Signed-off-by: Mauricio Faria de Oliveira 
Signed-off-by: Andrew Morton 
Reviewed-by: Ira Weiny 
Reviewed-by: Andrew Morton 
Cc: Jan Kara 
Link: http://lkml.kernel.org/r/20200218221716.1648-1-mfo@canonical.com
Signed-off-by: Linus Torvalds

mm/page-writeback.c: improve arithmetic divisions

2020-01-14T02:19:02+00:00

Use div64_ul() instead of do_div() if the divisor is unsigned long, to
avoid truncation to 32-bit on 64-bit platforms.

Link: http://lkml.kernel.org/r/20200102081442.8273-4-wenyang@linux.alibaba.com
Signed-off-by: Wen Yang 
Reviewed-by: Andrew Morton 
Cc: Qian Cai 
Cc: Tejun Heo 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds