Paolo noticed a cache line miss in UDP recvmsg() to access
sk_rxhash, sharing a cache line with sk_drops.

sk_drops might be heavily incremented by cpus handling a flood targeting
this socket.

We might place sk_drops on a separate cache line, but lets try
to avoid wasting 64 bytes per socket just for this, since we have
other bottlenecks to take care of.

sock_rps_record_flow() should only access sk_rxhash for connected
flows.

Testing sk_state for TCP_ESTABLISHED covers most of the cases for
connected sockets, for a zero cost, since system calls using
sock_rps_record_flow() also access sk->sk_prot which is on the
same cache line.

A follow up patch will provide a static_key (Jump Label) since most
hosts do not even use RFS.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch changes tun.c to call netif_receive_skb instead of netif_rx
when a packet is received (if CONFIG_4KSTACKS is not enabled to avoid
stack exhaustion). The difference between the two is that netif_rx queues
the packet into the backlog, and netif_receive_skb proccesses the packet
in the current context.

This patch is required for syzkaller [1] to collect coverage from packet
receive paths, when a packet being received through tun (syzkaller collects
coverage per process in the process context).

As mentioned by Eric this change also speeds up tun/tap. As measured by
Peter it speeds up his closed-loop single-stream tap/OVS benchmark by
about 23%, from 700k packets/second to 867k packets/second.

A similar patch was introduced back in 2010 [2, 3], but the author found
out that the patch doesn't help with the task he had in mind (for cgroups
to shape network traffic based on the original process) and decided not to
go further with it. The main concern back then was about possible stack
exhaustion with 4K stacks.

[1] https://github.com/google/syzkaller

[2] https://www.spinics.net/lists/netdev/thrd440.html#130570

[3] https://www.spinics.net/lists/netdev/msg130570.htmlSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Joe Perches says:

====================
irda: w83977af_ir: Neatening

Originally on top of Arnd's overly long udelay patches because I
noticed a misindented block.  That's now already fixed along with some
other whitespace problems.  These patches are the remainder style
issues from my original series.

Even though I haven't turned on the netwinder in a box in the
garage in who knows how long, if this device is still used somewhere,
might as well neaten the code too.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Use more common logging style, standardize function output logging use.

Miscellanea:

o Add and use pr_fmt
o Convert printks to pr_<level>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Neaten function declaration and definition arguments.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add braces where appropriate and remove an unnecessary else.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Convert pointer comparisons to NULL.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use a more typical vertical spacing style.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add spaces around operators.
git diff -w shows no differences.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Remove leading and trailing whitespace.
git diff -w shows no differences.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Pull sparc fix from David Miller:
 "A use-before-NULL-check from Dan Carpenter"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
  dbri: move dereference after check for NULL

We accidentally introduced a dereference before the NULL check in
xmit_descs() as part of silencing a GCC warning.

Fixes: 16f46050 ("dbri: Fix compiler warning")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Pull networking fixes from David Miller:

 1) When dcbnl_cee_fill() fails to be able to push a new netlink
    attribute, it return 0 instead of an error code. From Pan Bian.

 2) Two suffix handling fixes to FIB trie code, from Alexander Duyck.

 3) bnxt_hwrm_stat_ctx_alloc() goes through all the trouble of setting
    and maintaining a return code 'rc' but fails to actually return it.
    Also from Pan Bian.

 4) ping socket ICMP handler needs to validate ICMP header length, from
    Kees Cook.

 5) caif_sktinit_module() has this interesting logic:

        int err = sock_register(...);
        if (!err)
                return err;
        return 0;

    Just return sock_register()'s return value directly which is the
    only possible correct thing to do.

 6) Two bnx2x driver fixes from Yuval Mintz, return a reasonable
    estimate from get_ringparam() ethtool op when interface is down and
    avoid trying to use UDP port based tunneling on 577xx chips.

 7) Fix ep93xx_eth crash on module unload from Florian Fainelli.

 8) Missing uapi exports, from Stephen Hemminger.

 9) Don't schedule work from sk_destruct(), because the socket will be
    freed upon return from that function. From Herbert Xu.

10) Buggy drivers, of which we know there is at least one, can send a
    huge packet into the TCP stack but forget to set the gso_size in the
    SKB, which causes all kinds of problems.

    Correct this when it happens, and emit a one-time warning with the
    device name included so that it can be diagnosed more easily.

    From Marcelo Ricardo Leitner.

11) virtio-net does DMA off the stack causes hiccups with VMAP_STACK,
    fix from Andy Lutomirski.

12) Fix fec driver compilation with CONFIG_M5272, from Nikita
    Yushchenko.

13) mlx5 fixes from Kamal Heib, Saeed Mahameed, and Mohamad Haj Yahia.
    (erroneously flushing queues on error, module parameter validation,
    etc)

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (34 commits)
  net/mlx5e: Change the SQ/RQ operational state to positive logic
  net/mlx5e: Don't flush SQ on error
  net/mlx5e: Don't notify HW when filling the edge of ICO SQ
  net/mlx5: Fix query ISSI flow
  net/mlx5: Remove duplicate pci dev name print
  net/mlx5: Verify module parameters
  net: fec: fix compile with CONFIG_M5272
  be2net: Add DEVSEC privilege to SET_HSW_CONFIG command.
  virtio-net: Fix DMA-from-the-stack in virtnet_set_mac_address()
  tcp: warn on bogus MSS and try to amend it
  uapi glibc compat: fix outer guard of net device flags enum
  net: stmmac: clear reset value of snps, wr_osr_lmt/snps, rd_osr_lmt before writing
  netlink: Do not schedule work from sk_destruct
  uapi: export nf_log.h
  uapi: export tc_skbmod.h
  net: ep93xx_eth: Do not crash unloading module
  bnx2x: Prevent tunnel config for 577xx
  bnx2x: Correct ringparam estimate when DOWN
  isdn: hisax: set error code on failure
  net: bnx2x: fix improper return value
  ...

The shmem hole punching with fallocate(FALLOC_FL_PUNCH_HOLE) does not
want to race with generating new pages by faulting them in.

However, the wait-queue used to delay the page faulting has a serious
problem: the wait queue head (in shmem_fallocate()) is allocated on the
stack, and the code expects that "wake_up_all()" will make sure that all
the queue entries are gone before the stack frame is de-allocated.

And that is not at all necessarily the case.

Yes, a normal wake-up sequence will remove the wait-queue entry that
caused the wakeup (see "autoremove_wake_function()"), but the key
wording there is "that caused the wakeup".  When there are multiple
possible wakeup sources, the wait queue entry may well stay around.

And _particularly_ in a page fault path, we may be faulting in new pages
from user space while we also have other things going on, and there may
well be other pending wakeups.

So despite the "wake_up_all()", it's not at all guaranteed that all list
entries are removed from the wait queue head on the stack.

Fix this by introducing a new wakeup function that removes the list
entry unconditionally, even if the target process had already woken up
for other reasons.  Use that "synchronous" function to set up the
waiters in shmem_fault().

This problem has never been seen in the wild afaik, but Dave Jones has
reported it on and off while running trinity.  We thought we fixed the
stack corruption with the blk-mq rq_list locking fix (commit
7fe31130: "blk-mq: update hardware and software queues for sleeping
alloc"), but it turns out there was _another_ stack corruptor hiding
in the trinity runs.

Vegard Nossum (also running trinity) was able to trigger this one fairly
consistently, and made us look once again at the shmem code due to the
faults often being in that area.

Reported-and-tested-by: Vegard Nossum <vegard.nossum@oracle.com>.
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Saeed Mahameed says:

====================
Mellanox 100G mlx5 fixes 2016-12-04

Some bug fixes for mlx5 core and mlx5e driver.

v1->v2:
 - replace "uint" with "unsigned int"
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

When using the negative logic (i.e. FLUSH state), after the RQ/SQ reopen
we will have a time interval that the RQ/SQ is not really ready and the
state indicates that its not in FLUSH state because the initial SQ/RQ struct
memory starts as zeros.
Now we changed the state to indicate if the SQ/RQ is opened and we will
set the READY state after finishing preparing all the SQ/RQ resources.

Fixes: 6e8dd6d6 ("net/mlx5e: Don't wait for SQ completions on close")
Fixes: f2fde18c ("net/mlx5e: Don't wait for RQ completions on close")
Signed-off-by: Mohamad Haj Yahia <mohamad@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We are doing SQ descriptors cleanup in driver.

Fixes: 6e8dd6d6 ("net/mlx5e: Don't wait for SQ completions on close")
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We are going to do this a couple of steps ahead anyway.

Fixes: d3c9bc27 ("net/mlx5e: Added ICO SQs")
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

In old FWs query ISSI command is not supported and for some of those FWs
it might fail with status other than "MLX5_CMD_STAT_BAD_OP_ERR".

In such case instead of failing the driver load, we will treat any FW
status other than 0 for Query ISSI FW command as ISSI not supported and
assume ISSI=0 (most basic driver/FW interface).

In case of driver syndrom (query ISSI failure by driver) we will fail
driver load.

Fixes: f62b8bb8 ('net/mlx5: Extend mlx5_core to support ConnectX-4
Ethernet functionality')
Signed-off-by: Kamal Heib <kamalh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Remove duplicate pci dev name printing from mlx5_core_warn/dbg.

Fixes: 5a788398 ('net/mlx5_core: Improve mlx5 messages')
Signed-off-by: Kamal Heib <kamalh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Verify the mlx5_core module parameters by making sure that they are in
the expected range and if they aren't restore them to their default
values.

Fixes: 9603b61d ('mlx5: Move pci device handling from mlx5_ib to mlx5_core')
Signed-off-by: Kamal Heib <kamalh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch introduces the RX checksum function to check the
status of the hardware calculated checksum and its error and
appropriately convey status to the upper stack in skb->ip_summed
field.

In hardware, we only support checksum for the following
protocols:
1) IPv4,
2) TCP(over IPv4 or IPv6),
3) UDP(over IPv4 or IPv6),
4) SCTP(over IPv4 or IPv6)
but we support many L3(IPv4, IPv6, MPLS, PPPoE etc) and
L4(TCP, UDP, GRE, SCTP, IGMP, ICMP etc.) protocols.

Hardware limitation:
Our present hardware RX Descriptor lacks L3/L4 checksum
"Status & Error" bit (which usually can be used to indicate whether
checksum was calculated by the hardware and if there was any error
encountered during checksum calculation).

Software workaround:
We do get info within the RX descriptor about the kind of
L3/L4 protocol coming in the packet and the error status. These
errors might not just be checksum errors but could be related to
version, length of IPv4, UDP, TCP etc.
Because there is no-way of knowing if it is a L3/L4 error due
to bad checksum or any other L3/L4 error, we will not (cannot)
convey hardware checksum status(CHECKSUM_UNNECESSARY) for such
cases to upper stack and will not maintain the RX L3/L4 checksum
counters as well.
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit 80cca775 ("net: fec: cache statistics while device is down")
introduced unconditional statistics-related actions.

However, when driver is compiled with CONFIG_M5272, staticsics-related
definitions do not exist, which results into build errors.

Fix that by adding explicit handling of !defined(CONFIG_M5272) case.

Fixes: 80cca775 ("net: fec: cache statistics while device is down")
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

OPCODE_COMMON_GET_FN_PRIVILEGES is returning only DEVSEC
privilege (Unrestricted Administrative Privilege) for Lancer NIC functions.
So, driver is failing SET_HSW_CONFIG command, as DEVSEC privilege was not
set in the privilege bitmap. This patch fixes the problem by setting DEVSEC
privilege in SET_HSW_CONFIG’s privilege bitmap.
Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Signed-off-by: Suresh Reddy <suresh.reddy@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

With CONFIG_VMAP_STACK=y, virtnet_set_mac_address() can be passed a
pointer to the stack and it will OOPS.  Copy the address to the heap
to prevent the crash.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Laura Abbott <labbott@redhat.com>
Reported-by: zbyszek@in.waw.pl
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The budget split function requires the phy speed to be known.
While ndo open a phy speed identification is postponed till the
moment link is up. Hence, move it to appropriate callback, when link
is up.
Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Fixes: 8feb0a19 ("net: ethernet: ti: cpsw: split tx budget according between channels")
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Neal Cardwell says:
 If I am reading the code correctly, then I would have two concerns:
 1) Has that been tested? That seems like an extremely dramatic
    decrease in cwnd. For example, if the cwnd is 80, and there are 40
    ACKs, and half the ACKs are ECE marked, then my back-of-the-envelope
    calculations seem to suggest that after just 11 ACKs the cwnd would be
    down to a minimal value of 2 [..]
 2) That seems to contradict another passage in the draft [..] where it
    sazs:
       Just as specified in [RFC3168], DCTCP does not react to congestion
       indications more than once for every window of data.

Neal is right.  Fortunately we don't have to complicate this by testing
vs. current rtt estimate, we can just revert the patch.

Normal stack already handles this for us: receiving ACKs with ECE
set causes a call to tcp_enter_cwr(), from there on the ssthresh gets
adjusted and prr will take care of cwnd adjustment.

Fixes: 47805667 ("dctcp: update cwnd on congestion event")
Cc: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Vivien Didelot says:

====================
net: dsa: mv88e6xxx: rework reset and PPU code

Old Marvell chips (like 88E6060) don't have a PHY Polling Unit (PPU).

Next chips (like 88E6185) have a PPU, which has exclusive access to the
PHY registers, thus must be disabled before access.

Newer chips (like 88E6352) have an indirect mechanism to access the PHY
registers whenever, thus loose control over the PPU (always enabled).

Here's a summary:

Model | PPU? | Has PPU ctrl?  | PPU state readable? | PHY access
----- | ---- | -------------- | ------------------- | ----------
 6060 | no   | no             | no                  | direct
 6185 | yes  | yes, PPUEn bit | yes, PPUState 2-bit | direct w/ PPU dis.
 6352 | yes  | no             | yes, PPUState 1-bit | indirect
 6390 | yes  | no             | yes, InitState bit  | indirect

Depending on the PPU control, a switch may have to restart the PPU when
resetting the switch. Once the switch is reset, we must wait for the PPU
state to be active polling again before accessing the registers.

For that purpose, add new operations to the chips to enable/disable the
PPU, and execute software reset. With these new ops in place, rework the
switch reset code and finally get rid of the MV88E6XXX_FLAG_PPU* flags.

Changes in v3:
  - consider 6097 as 6352 (no PPU ops and use mv88e6352_g1_reset).

Changes in v2:
  - wait in ppu/reset ops so that ppu_polling is not needed anymore.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Some Marvell chips can enable/disable the PPU on demand. This is needed
to access the PHY registers when there is no indirection mechanism.

Add two new ppu_enable and ppu_disable ops to describe this and finally
get rid of the MV88E6XXX_FLAG_PPU* flags.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Marvell chips have different way to issue a software reset.

Old chips (such as 88E6060) have a reset bit in an ATU control register.

Newer chips moved this bit in a Global control register. Chips with
controllable PPU should reset the PPU when resetting the switch.

Add a new reset operation to implement these differences and introduce a
mv88e6xxx_software_reset() helper to wrap it conveniently.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add an helper to toggle the eventual GPIO connected to the reset pin.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Before resetting a switch, the ports should be set to the Disabled state
and the transmit queues should be drained.

Add an helper to explicit that.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Lino Sanfilippo says:

====================
Gigabit ethernet driver for Alacritechs SLIC devices (v4)

this is the forth version of the slicoss gigabit ethernet driver (which is a
rework of the driver from Alacritech which can currently be found under
drivers/staging/slicoss). The driver is supposed to support Mojave, Oasis and
Kalahari cards, for both copper and fiber.

If this code is accepted the staging version can be removed.

The driver has been tested on a SEN2104ET adapter (4 Port PCIe copper).

v4:
- fix wrong driver name in Kconfig file (reported by Rami Rosen)
- remove unused variable from driver struct (reported by Rami Rosen)
- return "err" instead of 0 in slic_load_rcvseq_firmware() (reported by Rami Rosen)
- Fix typos in constants, comments and error message (reported by Markus Böhme)
- fix various warnings concerning signedness (reported by Markus Böhme)
- improve line formatting (reported by Markus Böhme)
- add comment describing the need for SLIC_MAX_TX_COMPLETIONS (suggested by Florian Fainelli)
- do not zero out complete rx descriptor (suggested by Florian Fainelli)
- add missing write barrier (reported by Florian Fainelli)
- remove unneeded assignment of net_device to skb (reported by Florian Fainelli)
- use napi_complete_done() instead of napi_complete (suggested by Florian Fainelli)
- use napi_schedule_irqoff() instead of napi_schedule (suggested by Florian Fainelli)
- do not map error returned by slic_init() to -ENOMEM
- do proper dma syncs before and after rx descriptor status is set to 0
- if after dma sync for CPU rx descriptor is not used return it to HW by means of dma sync for device

v3:
- dont add defines to pci_ids.h but instead put it into the drivers header file
(requested by Greg Kroah-Hartman)

v2:
- remove unusual padding in statistic strings (suggested by Andrew Lunn)
- for mdio register and bit names use defines from mii.h instead of own ones
  (suggested by Andrew Lunn)
- remove unused defines
- ensure PCI flush at two more places
- use mmiowb before lock to prevent mmio writes leaking out of lock
- fix some typos in comments
- add copyright and GPL header
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Add myself as maintainer for the slicoss ethernet driver.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add driver for Alacritech gigabit ethernet cards with SLIC (session-layer
interface control) technology. The driver provides basic support without
SLIC for the following devices:

- Mojave cards (single port PCI Gigabit) both copper and fiber
- Oasis cards (single and dual port PCI-x Gigabit) copper and fiber
- Kalahari cards (dual and quad port PCI-e Gigabit) copper and fiber
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

There have been some reports lately about TCP connection stalls caused
by NIC drivers that aren't setting gso_size on aggregated packets on rx
path. This causes TCP to assume that the MSS is actually the size of the
aggregated packet, which is invalid.

Although the proper fix is to be done at each driver, it's often hard
and cumbersome for one to debug, come to such root cause and report/fix
it.

This patch amends this situation in two ways. First, it adds a warning
on when this situation occurs, so it gives a hint to those trying to
debug this. It also limit the maximum probed MSS to the adverised MSS,
as it should never be any higher than that.

The result is that the connection may not have the best performance ever
but it shouldn't stall, and the admin will have a hint on what to look
for.

Tested with virtio by forcing gso_size to 0.

v2: updated msg per David's suggestion
v3: use skb_iif to find the interface and also log its name, per Eric
    Dumazet's suggestion. As the skb may be backlogged and the interface
    gone by then, we need to check if the number still has a meaning.
v4: use helper tcp_gro_dev_warn() and avoid pr_warn_once inside __once, per
    David's suggestion

Cc: Jonathan Maxwell <jmaxwell37@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Fix a wrong condition preventing the higher net device flags
IFF_LOWER_UP etc to be defined if net/if.h is included before
linux/if.h.

The comment makes it clear the intention was to allow partial
definition with either parts.

This fixes compilation of userspace programs trying to use
IFF_LOWER_UP, IFF_DORMANT or IFF_ECHO.

Fixes: 4a91cb61 ("uapi glibc compat: fix compile errors when glibc net/if.h included before linux/if.h")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Mikko Rapeli <mikko.rapeli@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

In UDP recvmsg() path we currently access 3 cache lines from an skb
while holding receive queue lock, plus another one if packet is
dequeued, since we need to change skb->next->prev

1st cache line (contains ->next/prev pointers, offsets 0x00 and 0x08)
2nd cache line (skb->len & skb->peeked, offsets 0x80 and 0x8e)
3rd cache line (skb->truesize/users, offsets 0xe0 and 0xe4)

skb->peeked is only needed to make sure 0-length packets are properly
handled while MSG_PEEK is operated.

I had first the intent to remove skb->peeked but the "MSG_PEEK at
non-zero offset" support added by Sam Kumar makes this not possible.

This patch avoids one cache line miss during the locked section, when
skb->len and skb->peeked do not have to be read.

It also avoids the skb_set_peeked() cost for non empty UDP datagrams.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

WR_OSR_LMT and RD_OSR_LMT have a reset value of 1.
Since the reset value wasn't cleared before writing, the value in the
register would be incorrect if specifying an uneven value for
snps,wr_osr_lmt/snps,rd_osr_lmt.

Zero is a valid value for the properties, since the databook specifies:
maximum outstanding requests = WR_OSR_LMT + 1.

We do not want to change the behavior for existing users when the
property is missing. Therefore, default to 1 if the property is missing,
since that is the same as the reset value.
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>