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  1. 14 1月, 2011 2 次提交
  3. 13 1月, 2011 25 次提交
  5. 07 1月, 2011 13 次提交
    • N
      fs: scale mntget/mntput · b3e19d92
      由 Nick Piggin 提交于 
      The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.

The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.

We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.

- check the global sum once every interval (this will delay zero detection
  for some interval, so it's probably a showstopper for vfsmounts).

- keep a local count and only taking the global sum when local reaches 0 (this
  is difficult for vfsmounts, because we can't hold preempt off for the life of
  a reference, so a counter would need to be per-thread or tied strongly to a
  particular CPU which requires more locking).

- keep a local difference of increments and decrements, which allows us to sum
  the total difference and hence find the refcount when summing all CPUs. Then,
  keep a single integer "long" refcount for slow and long lasting references,
  and only take the global sum of local counters when the long refcount is 0.

This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.

This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.

This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
      b3e19d92
    • N
      fs: improve scalability of pseudo filesystems · 4b936885
      由 Nick Piggin 提交于 
      Regardless of how much we possibly try to scale dcache, there is likely
always going to be some fundamental contention when adding or removing children
under the same parent. Pseudo filesystems do not seem need to have connected
dentries because by definition they are disconnected.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
      4b936885
    • N
      fs: dcache reduce branches in lookup path · fb045adb
      由 Nick Piggin 提交于 
      Reduce some branches and memory accesses in dcache lookup by adding dentry
flags to indicate common d_ops are set, rather than having to check them.
This saves a pointer memory access (dentry->d_op) in common path lookup
situations, and saves another pointer load and branch in cases where we
have d_op but not the particular operation.

Patched with:

git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
      fb045adb
    • N
      fs: avoid inode RCU freeing for pseudo fs · ff0c7d15
      由 Nick Piggin 提交于 
      Pseudo filesystems that don't put inode on RCU list or reachable by
rcu-walk dentries do not need to RCU free their inodes.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
      ff0c7d15
    • N
      fs: icache RCU free inodes · fa0d7e3d
      由 Nick Piggin 提交于 
      RCU free the struct inode. This will allow:

- Subsequent store-free path walking patch. The inode must be consulted for
  permissions when walking, so an RCU inode reference is a must.
- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- Could remove some nested trylock loops in dcache code
- Could potentially simplify things a bit in VM land. Do not need to take the
  page lock to follow page->mapping.

The downsides of this is the performance cost of using RCU. In a simple
creat/unlink microbenchmark, performance drops by about 10% due to inability to
reuse cache-hot slab objects. As iterations increase and RCU freeing starts
kicking over, this increases to about 20%.

In cases where inode lifetimes are longer (ie. many inodes may be allocated
during the average life span of a single inode), a lot of this cache reuse is
not applicable, so the regression caused by this patch is smaller.

The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU,
however this adds some complexity to list walking and store-free path walking,
so I prefer to implement this at a later date, if it is shown to be a win in
real situations. I haven't found a regression in any non-micro benchmark so I
doubt it will be a problem.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
      fa0d7e3d
    • N
      fs: change d_delete semantics · fe15ce44
      由 Nick Piggin 提交于 
      Change d_delete from a dentry deletion notification to a dentry caching
advise, more like ->drop_inode. Require it to be constant and idempotent,
and not take d_lock. This is how all existing filesystems use the callback
anyway.

This makes fine grained dentry locking of dput and dentry lru scanning
much simpler.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>
      fe15ce44
    • C
      net: bridge: check the length of skb after nf_bridge_maybe_copy_header() · f88de8de
      由 Changli Gao 提交于 
      Since nf_bridge_maybe_copy_header() may change the length of skb,
we should check the length of skb after it to handle the ppoe skbs.
Signed-off-by: NChangli Gao <xiaosuo@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      f88de8de
    • P
      netfilter: fix export secctx error handling · cba85b53
      由 Pablo Neira Ayuso 提交于 
      In 1ae4de0c, the secctx was exported
via the /proc/net/netfilter/nf_conntrack and ctnetlink interfaces
instead of the secmark.

That patch introduced the use of security_secid_to_secctx() which may
return a non-zero value on error.

In one of my setups, I have NF_CONNTRACK_SECMARK enabled but no
security modules. Thus, security_secid_to_secctx() returns a negative
value that results in the breakage of the /proc and `conntrack -L'
outputs. To fix this, we skip the inclusion of secctx if the
aforementioned function fails.

This patch also fixes the dynamic netlink message size calculation
if security_secid_to_secctx() returns an error, since its logic is
also wrong.

This problem exists in Linux kernel >= 2.6.37.
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      cba85b53
    • C
      netfilter: fix the race when initializing nf_ct_expect_hash_rnd · f682cefa
      由 Changli Gao 提交于 
      Since nf_ct_expect_dst_hash() may be called without nf_conntrack_lock
locked, nf_ct_expect_hash_rnd should be initialized in the atomic way.

In this patch, we use nf_conntrack_hash_rnd instead of
nf_ct_expect_hash_rnd.
Signed-off-by: NChangli Gao <xiaosuo@gmail.com>
Acked-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      f682cefa
    • E
      ipv4: IP defragmentation must be ECN aware · 6623e3b2
      由 Eric Dumazet 提交于 
      RFC3168 (The Addition of Explicit Congestion Notification to IP)
states :

5.3.  Fragmentation

   ECN-capable packets MAY have the DF (Don't Fragment) bit set.
   Reassembly of a fragmented packet MUST NOT lose indications of
   congestion.  In other words, if any fragment of an IP packet to be
   reassembled has the CE codepoint set, then one of two actions MUST be
   taken:

      * Set the CE codepoint on the reassembled packet.  However, this
        MUST NOT occur if any of the other fragments contributing to
        this reassembly carries the Not-ECT codepoint.

      * The packet is dropped, instead of being reassembled, for any
        other reason.

This patch implements this requirement for IPv4, choosing the first
action :

If one fragment had NO-ECT codepoint
        reassembled frame has NO-ECT
ElIf one fragment had CE codepoint
        reassembled frame has CE
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      6623e3b2
    • D
      dcb: use after free in dcb_flushapp() · 2a8fe003
      由 Dan Carpenter 提交于 
      The original code has a use after free bug because it's not using the
_safe() version of the list_for_each_entry() macro.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      2a8fe003
    • D
      dcb: unlock on error in dcbnl_ieee_get() · 70bfa2d2
      由 Dan Carpenter 提交于 
      There is a "goto nla_put_failure" hidden inside the NLA_PUT() macro, but
we're holding the dcb_lock so we need to unlock first.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      70bfa2d2
    • E
      net: add POLLPRI to sock_def_readable() · 2c6607c6
      由 Eric Dumazet 提交于 
      Leonardo Chiquitto found poll() could block forever on tcp sockets and
Urgent data was received, if the event flag only contains POLLPRI.

He did a bisection and found commit 4938d7e0 (poll: avoid extra
wakeups in select/poll) was the source of the problem.

Problem is TCP sockets use standard sock_def_readable() function for
their sk_data_ready() handler, and sock_def_readable() doesnt signal
POLLPRI.

Only TCP is affected by the problem. Adding POLLPRI to the list of flags
might trigger unnecessary schedules, but URGENT handling is such a
seldom used feature this seems a good compromise.

Thanks a lot to Leonardo for providing the bisection result and a test
program as well.

Reference : http://www.spinics.net/lists/netdev/msg151793.htmlReported-and-bisected-by: NLeonardo Chiquitto <leonardo.lists@gmail.com>
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Tested-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      2c6607c6