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This patch introduces a new mesh configuration parameter "ht_opmode" and will
allow user to check the current HT protection mode selected. Users could
configure the protection mode by the command "iw mesh_iface set mesh_param
mesh_ht_protection_mode=2". The default protection mode of mesh is set to
non-HT mixed mode.
Signed-off-by: Ashok Nagarajan <ashok@cozybit.com>
Reviewed-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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This adds hooks to call into the driver to get additional
stats for the ethtool API.
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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This patch adds a 64-bit flags2 features member to struct mlx4_dev to
export further features of the hardware. The original flags field
tracks features whose support bits are advertised by the firmware in
offsets 0x40 and 0x44 of the query device capabilities command.
flags2 will track features whose support bits are scattered at various
offsets.
RSS support is the first feature to be exported through flags2. RSS
capabilities are located at offset 0x2e. The size of the RSS
indirection table is also given in this offset.
Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
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Otherwise CM packets going over MLX QP1 get fixed scheduling priority 0.
We want CM packets to get the same scheduling priority, and therefore
map to the same SQ (Schedule Queue) and eventually TC (Traffic Class),
as the application requested for the actual QP used for the connection.
Signed-off-by: Oren Duer <oren@mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
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This patch removes ip_queue support which was marked as obsolete
years ago. The nfnetlink_queue modules provides more advanced
user-space packet queueing mechanism.
This patch also removes capability code included in SELinux that
refers to ip_queue. Otherwise, we break compilation.
Several warning has been sent regarding this to the mailing list
in the past month without anyone rising the hand to stop this
with some strong argument.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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IB_QPT_RAW_PACKET allows applications to build a complete packet,
including L2 headers, when sending; on the receive side, the HW will
not strip any headers.
This QP type is designed for userspace direct access to Ethernet; for
example by applications that do TCP/IP themselves. Only processes
with the NET_RAW capability are allowed to create raw packet QPs (the
name "raw packet QP" is supposed to suggest an analogy to AF_PACKET /
SOL_RAW sockets).
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
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Just as we don't allow PDs, CQs, etc. to be destroyed if there are QPs
that are attached to them, don't let a QP be destroyed if there are
multicast group(s) attached to it. Use the existing usecnt field of
struct ib_qp which was added by commit 0e0ec7e ("RDMA/core: Export
ib_open_qp() to share XRC TGT QPs") to track this.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
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Explicit helper attachment via the CT target is broken with NAT
if non-standard ports are used. This problem was hidden behind
the automatic helper assignment routine. Thus, it becomes more
noticeable now that we can disable the automatic helper assignment
with Eric Leblond's:
9e8ac5a netfilter: nf_ct_helper: allow to disable automatic helper assignment
Basically, nf_conntrack_alter_reply asks for looking up the helper
up if NAT is enabled. Unfortunately, we don't have the conntrack
template at that point anymore.
Since we don't want to rely on the automatic helper assignment,
we can skip the second look-up and stick to the helper that was
attached by iptables. With the CT target, the user is in full
control of helper attachment, thus, the policy is to trust what
the user explicitly configures via iptables (no automatic magic
anymore).
Interestingly, this bug was hidden by the automatic helper look-up
code. But it can be easily trigger if you attach the helper in
a non-standard port, eg.
iptables -I PREROUTING -t raw -p tcp --dport 8888 \
-j CT --helper ftp
And you disabled the automatic helper assignment.
I added the IPS_HELPER_BIT that allows us to differenciate between
a helper that has been explicitly attached and those that have been
automatically assigned. I didn't come up with a better solution
(having backward compatibility in mind).
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Allow master and backup servers to use many threads
for sync traffic. Add sysctl var "sync_ports" to define the
number of threads. Every thread will use single UDP port,
thread 0 will use the default port 8848 while last thread
will use port 8848+sync_ports-1.
The sync traffic for connections is scheduled to many
master threads based on the cp address but one connection is
always assigned to same thread to avoid reordering of the
sync messages.
Remove ip_vs_sync_switch_mode because this check
for sync mode change is still risky. Instead, check for mode
change under sync_buff_lock.
Make sure the backup socks do not block on reading.
Special thanks to Aleksey Chudov for helping in all tests.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Tested-by: Aleksey Chudov <aleksey.chudov@gmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
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Add two new sysctl vars to control the sync rate with the
main idea to reduce the rate for connection templates because
currently it depends on the packet rate for controlled connections.
This mechanism should be useful also for normal connections
with high traffic.
sync_refresh_period: in seconds, difference in reported connection
timer that triggers new sync message. It can be used to
avoid sync messages for the specified period (or half of
the connection timeout if it is lower) if connection state
is not changed from last sync.
sync_retries: integer, 0..3, defines sync retries with period of
sync_refresh_period/8. Useful to protect against loss of
sync messages.
Allow sysctl_sync_threshold to be used with
sysctl_sync_period=0, so that only single sync message is sent
if sync_refresh_period is also 0.
Add new field "sync_endtime" in connection structure to
hold the reported time when connection expires. The 2 lowest
bits will represent the retry count.
As the sysctl_sync_period now can be 0 use ACCESS_ONCE to
avoid division by zero.
Special thanks to Aleksey Chudov for being patient with me,
for his extensive reports and helping in all tests.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Tested-by: Aleksey Chudov <aleksey.chudov@gmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
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High rate of sync messages in master can lead to
overflowing the socket buffer and dropping the messages.
Fixed sleep of 1 second without wakeup events is not suitable
for loaded masters,
Use delayed_work to schedule sending for queued messages
and limit the delay to IPVS_SYNC_SEND_DELAY (20ms). This will
reduce the rate of wakeups but to avoid sending long bursts we
wakeup the master thread after IPVS_SYNC_WAKEUP_RATE (8) messages.
Add hard limit for the queued messages before sending
by using "sync_qlen_max" sysctl var. It defaults to 1/32 of
the memory pages but actually represents number of messages.
It will protect us from allocating large parts of memory
when the sending rate is lower than the queuing rate.
As suggested by Pablo, add new sysctl var
"sync_sock_size" to configure the SNDBUF (master) or
RCVBUF (slave) socket limit. Default value is 0 (preserve
system defaults).
Change the master thread to detect and block on
SNDBUF overflow, so that we do not drop messages when
the socket limit is low but the sync_qlen_max limit is
not reached. On ENOBUFS or other errors just drop the
messages.
Change master thread to enter TASK_INTERRUPTIBLE
state early, so that we do not miss wakeups due to messages or
kthread_should_stop event.
Thanks to Pablo Neira Ayuso for his valuable feedback!
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
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As the goal is to mirror the inactconns/activeconns
counters in the backup server, make sure the cp->flags are
updated even if cp is still not bound to dest. If cp->flags
are not updated ip_vs_bind_dest will rely only on the initial
flags when updating the counters. To avoid mistakes and
complicated checks for protocol state rely only on the
IP_VS_CONN_F_INACTIVE bit when updating the counters.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Tested-by: Aleksey Chudov <aleksey.chudov@gmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
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this_cpu_inc() is IRQ safe and faster than
local_bh_disable()/__this_cpu_inc()/local_bh_enable(), at least on x86.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch allows you to disable automatic conntrack helper
lookup based on TCP/UDP ports, eg.
echo 0 > /proc/sys/net/netfilter/nf_conntrack_helper
[ Note: flows that already got a helper will keep using it even
if automatic helper assignment has been disabled ]
Once this behaviour has been disabled, you have to explicitly
use the iptables CT target to attach helper to flows.
There are good reasons to stop supporting automatic helper
assignment, for further information, please read:
http://www.netfilter.org/news.html#2012-04-03
This patch also adds one message to inform that automatic helper
assignment is deprecated and it will be removed soon (this is
spotted only once, with the first flow that gets a helper attached
to make it as less annoying as possible).
Signed-off-by: Eric Leblond <eric@regit.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Use devres to implement dev_get_regmap(). This should mean that in almost
all cases devices wishing to take advantage of framework features based on
regmap shouldn't need to explicitly pass the regmap into the framework.
This simplifies device setup a bit.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
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Make the return value explicitly true or false.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Reason: Pull in the separate branch which was created so arch/tile can
base further work on it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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These flags can be useful for extra allocations outside of the core
code.
Add __GFP_NOTRACK to them, so the archs which have kmemcheck do
not have to provide extra allocators just for that reason.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120505150141.428211694@linutronix.de
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Will replace the misnomed cpu_idle_wait() function which is copied a
gazillion times all over arch/*
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120507175652.049316594@linutronix.de
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Conflicts:
drivers/net/ethernet/intel/e1000e/param.c
drivers/net/wireless/iwlwifi/iwl-agn-rx.c
drivers/net/wireless/iwlwifi/iwl-trans-pcie-rx.c
drivers/net/wireless/iwlwifi/iwl-trans.h
Resolved the iwlwifi conflict with mainline using 3-way diff posted
by John Linville and Stephen Rothwell. In 'net' we added a bug
fix to make iwlwifi report a more accurate skb->truesize but this
conflicted with RX path changes that happened meanwhile in net-next.
In e1000e a conflict arose in the validation code for settings of
adapter->itr. 'net-next' had more sophisticated logic so that
logic was used.
Signed-off-by: David S. Miller <davem@davemloft.net>
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This patch adds a somewhat generic framework for MDIO bus
multiplexers. It is modeled on the I2C multiplexer.
The multiplexer is needed if there are multiple PHYs with the same
address connected to the same MDIO bus adepter, or if there is
insufficient electrical drive capability for all the connected PHY
devices.
Conceptually it could look something like this:
------------------
| Control Signal |
--------+---------
|
--------------- --------+------
| MDIO MASTER |---| Multiplexer |
--------------- --+-------+----
| |
C C
h h
i i
l l
d d
| |
--------- A B ---------
| | | | | |
| PHY@1 +-------+ +---+ PHY@1 |
| | | | | |
--------- | | ---------
--------- | | ---------
| | | | | |
| PHY@2 +-------+ +---+ PHY@2 |
| | | |
--------- ---------
This framework configures the bus topology from device tree data. The
mechanics of switching the multiplexer is left to device specific
drivers.
The follow-on patch contains a multiplexer driven by GPIO lines.
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Add of_mdio_find_bus() which allows an mii_bus to be located given its
associated the device tree node.
This is needed by the follow-on patch to add a driver for MDIO bus
multiplexers.
The of_mdiobus_register() function is modified so that the device tree
node is recorded in the mii_bus. Then we can find it again by
iterating over all mdio_bus_class devices.
Because the OF device tree has now become an integral part of the
kernel, this can live in mdio_bus.c (which contains the needed
mdio_bus_class structure) instead of of_mdio.c.
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Neither compare_ether_addr() nor compare_ether_addr_64bits()
(as it can fall back to the former) have comparison semantics
like memcmp() where the sign of the return value indicates sort
order. We had a bug in the wireless code due to a blind memcmp
replacement because of this.
A cursory look suggests that the wireless bug was the only one
due to this semantic difference.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Add resource_overlaps(), which returns true if two resources overlap at all.
Use this to replace the complicated check in coalesce_windows().
Signed-Off-By: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
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Remove the Intel specific interfaces from dmar.h and remove
asm/irq_remapping.h which is only used for io_apic.c anyway.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
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The operation for releasing a remapping entry is iommu
specific too.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
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Convert these calls too:
* Disable of remapping hardware
* Reenable of remapping hardware
* Enable fault handling
With that all of arch/x86/kernel/apic/apic.c is converted to
use the generic intr-remapping interface.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
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This patch introduces irq_remap_ops to hold implementation
specific function pointer to handle interrupt remapping. As
the first part the initialization functions for VT-d are
converted to these ops.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
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Now that tasks are gone we are guaranteed to only get a single completion
per command, and thus don't need this counter.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Now that tasks are gone we are guaranteed to only get a single completion
per command, and thus don't need this counter.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Now that tasks are gone we are guaranteed to only get a single completion
per command, and thus don't need this counter.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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We can use struct se_cmd for everything it did. Make sure to pass the S/G
list and data direction to the execution function to ease adding back BIDI
support later on.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Now that we only have a single task per command we can use a direct pointer
to it instead of list.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Make CDB emulation work on commands instead of tasks again as a preparation
of removing tasks completely.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Remove the task_sectors field that isn't used anywhere.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Now that we don't split commands the size field in the task is always
equivalent to the one in the CDB, even in cases where we have two tasks
due to a BIDI transfer. Just refer the the size in the command instead
of duplicating it in the task.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Now that we don't split commands the lba field in the task is always
equivalent to the one in the CDB, even in cases where we have two tasks
due to a BIDI transfer. Just refer the the lba in the command instead
of duplicating it in the task.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Now that tasks are always the same size as the command there is no need
to rewrite a CDB in common code. Notw that we keep the separately allocated
CDB in the pscsi and stgt backends for now, to easy reintroducing any
command splitting local to these backends if nessecary.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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The VM accounting makes no sense at this level, and half of the callers
didn't ever actually use the end result. The only time we want to
unaccount the memory is when we actually remove the vma, so do the
accounting at that point instead.
This simplifies the interfaces (no need to pass down that silly page
counter to functions that really don't care), and also makes it much
more obvious what is actually going on: we do vm_[un]acct_memory() when
adding or removing the vma, not on random page walking.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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None of the callers want to pass in 'zap_details', and it doesn't even
make sense for the case of actually unmapping vma's. So remove the
argument, and clean up the interface.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes form Peter Anvin
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
intel_mid_powerbtn: mark irq as IRQF_NO_SUSPEND
arch/x86/platform/geode/net5501.c: change active_low to 0 for LED driver
x86, relocs: Remove an unused variable
asm-generic: Use __BITS_PER_LONG in statfs.h
x86/amd: Re-enable CPU topology extensions in case BIOS has disabled it
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With the recent changes for how we compute the skb truesize it occurs to me
we are probably going to have a lot of calls to skb_end_pointer -
skb->head. Instead of running all over the place doing that it would make
more sense to just make it a separate inline skb_end_offset(skb) that way
we can return the correct value without having gcc having to do all the
optimization to cancel out skb->head - skb->head.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux
Pull an ACPI patch from Len Brown:
"It fixes a D3 issue new in 3.4-rc1."
By Lin Ming via Len Brown:
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
ACPI: Fix D3hot v D3cold confusion
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Before this patch, ACPI_STATE_D3 incorrectly referenced D3hot
in some places, but D3cold in other places.
After this patch, ACPI_STATE_D3 always means ACPI_STATE_D3_COLD;
and all references to D3hot use ACPI_STATE_D3_HOT.
ACPI's _PR3 method is used to enter both D3hot and D3cold states.
What distinguishes D3hot from D3cold is the presence _PR3
(Power Resources for D3hot) If these resources are all ON,
then the state is D3hot. If _PR3 is not present,
or all _PR0 resources for the devices are OFF,
then the state is D3cold.
This patch applies after Linux-3.4-rc1.
A future syntax cleanup may remove ACPI_STATE_D3
to emphasize that it always means ACPI_STATE_D3_COLD.
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Aaron Lu <aaron.lu@amd.com>
Signed-off-by: Len Brown <len.brown@intel.com>
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The calling conventions for __d_lookup_rcu() and dentry_cmp() are
annoying in different ways, and there is actually one single underlying
reason for both of the annoyances.
The fundamental reason is that we do the returned dentry sequence number
check inside __d_lookup_rcu() instead of doing it in the caller. This
results in two annoyances:
- __d_lookup_rcu() now not only needs to return the dentry and the
sequence number that goes along with the lookup, it also needs to
return the inode pointer that was validated by that sequence number
check.
- and because we did the sequence number check early (to validate the
name pointer and length) we also couldn't just pass the dentry itself
to dentry_cmp(), we had to pass the counted string that contained the
name.
So that sequence number decision caused two separate ugly calling
conventions.
Both of these problems would be solved if we just did the sequence
number check in the caller instead. There's only one caller, and that
caller already has to do the sequence number check for the parent
anyway, so just do that.
That allows us to stop returning the dentry->d_inode in that in-out
argument (pointer-to-pointer-to-inode), so we can make the inode
argument just a regular input inode pointer. The caller can just load
the inode from dentry->d_inode, and then do the sequence number check
after that to make sure that it's synchronized with the name we looked
up.
And it allows us to just pass in the dentry to dentry_cmp(), which is
what all the callers really wanted. Sure, dentry_cmp() has to be a bit
careful about the dentry (which is not stable during RCU lookup), but
that's actually very simple.
And now that dentry_cmp() can clearly see that the first string argument
is a dentry, we can use the direct word access for that, instead of the
careful unaligned zero-padding. The dentry name is always properly
aligned, since it is a single path component that is either embedded
into the dentry itself, or was allocated with kmalloc() (see __d_alloc).
Finally, this also uninlines the nasty slow-case for dentry comparisons:
that one *does* need to do a sequence number check, since it will call
in to the low-level filesystems, and we want to give those a stable
inode pointer and path component length/start arguments. Doing an extra
sequence check for that slow case is not a problem, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The normal read_seqcount_begin() function will wait for any current
writers to exit their critical region by looping until the sequence
count is even.
That "wait for sequence count to stabilize" is the right thing to do if
the read-locker will just retry the whole operation on contention: no
point in doing a potentially expensive reader sequence if we know at the
beginning that we'll just end up re-doing it all.
HOWEVER. Some users don't actually retry the operation, but instead
will abort and do the operation with proper locking. So the sequence
count case may be the optimistic quick case, but in the presense of
writers you may want to do full locking in order to guarantee forward
progress. The prime example of this would be the RCU name lookup.
And in that case, you may well be better off without the "retry early",
and are in a rush to instead get to the failure handling. Thus this
"raw" interface that just returns the sequence number without testing it
- it just forces the low bit to zero so that read_seqcount_retry() will
always fail such a "active concurrent writer" scenario.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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