Introduce a type of hlist that can support the use of the lowest bit in the
hlist_head. This will be subsequently used to implement per-bucket bit spinlock
for inode and dentry hashes, and may be useful in other cases such as network
hashes.
Reviewed-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

This simple implementation just checks for no ACLs on the inode, and
if so, then the rcu-walk may proceed, otherwise fail it.

This could easily be extended to put acls under RCU and check them
under seqlock, if need be. But this implementation is enough to show
the rcu-walk aware permissions code for path lookups is working, and
will handle cases where there are no ACLs or ACLs in just the final
element.

This patch implicity converts tmpfs to rcu-aware permission check.
Subsequent patches onvert ext*, xfs, and, btrfs. Each of these uses
acl/permission code in a different way, so convert them all to provide
templates and proof of concept.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Require filesystems be aware of .d_revalidate being called in rcu-walk
mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning
-ECHILD from all implementations.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Put dentry and inode fields into top of data structure.  This allows RCU path
traversal to perform an RCU dentry lookup in a path walk by touching only the
first 56 bytes of the dentry.

We also fit in 8 bytes of inline name in the first 64 bytes, so for short
names, only 64 bytes needs to be touched to perform the lookup. We should
get rid of the hash->prev pointer from the first 64 bytes, and fit 16 bytes
of name in there, which will take care of 81% rather than 32% of the kernel
tree.

inode is also rearranged so that RCU lookup will only touch a single cacheline
in the inode, plus one in the i_ops structure.

This is important for directory component lookups in RCU path walking. In the
kernel source, directory names average is around 6 chars, so this works.

When we reach the last element of the lookup, we need to lock it and take its
refcount which requires another cacheline access.

Align dentry and inode operations structs, so members will be at predictable
offsets and we can group common operations into head of structure.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

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>

Rather than keep a d_mounted count in the dentry, set a dentry flag instead.
The flag can be cleared by checking the hash table to see if there are any
mounts left, which is not time critical because it is performed at detach time.

The mounted state of a dentry is only used to speculatively take a look in the
mount hash table if it is set -- before following the mount, vfsmount lock is
taken and mount re-checked without races.

This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I
might use later (and some configs have larger than 32-bit spinlocks which might
make use of the hole).

Autofs4 conversion and changelog by Ian Kent <raven@themaw.net>:
In autofs4, when expring direct (or offset) mounts we need to ensure that we
block user path walks into the autofs mount, which is covered by another mount.
To do this we clear the mounted status so that follows stop before walking into
the mount and are essentially blocked until the expire is completed. The
automount daemon still finds the correct dentry for the umount due to the
follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as
an inode operation for direct and offset mounts only and is called following
the lookup that stopped at the covered mount.

At the end of the expire the covering mount probably has gone away so the
mounted status need not be restored. But we need to check this and only restore
the mounted status if the expire failed.

XXX: autofs may not work right if we have other mounts go over the top of it?
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Use a seqlock in the fs_struct to enable us to take an atomic copy of the
complete cwd and root paths. Use this in the RCU lookup path to avoid a
thread-shared spinlock in RCU lookup operations.

Multi-threaded apps may now perform path lookups with scalability matching
multi-process apps. Operations such as stat(2) become very scalable for
multi-threaded workload.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Perform common cases of path lookups without any stores or locking in the
ancestor dentry elements. This is called rcu-walk, as opposed to the current
algorithm which is a refcount based walk, or ref-walk.

This results in far fewer atomic operations on every path element,
significantly improving path lookup performance. It also avoids cacheline
bouncing on common dentries, significantly improving scalability.

The overall design is like this:
* LOOKUP_RCU is set in nd->flags, which distinguishes rcu-walk from ref-walk.
* Take the RCU lock for the entire path walk, starting with the acquiring
  of the starting path (eg. root/cwd/fd-path). So now dentry refcounts are
  not required for dentry persistence.
* synchronize_rcu is called when unregistering a filesystem, so we can
  access d_ops and i_ops during rcu-walk.
* Similarly take the vfsmount lock for the entire path walk. So now mnt
  refcounts are not required for persistence. Also we are free to perform mount
  lookups, and to assume dentry mount points and mount roots are stable up and
  down the path.
* Have a per-dentry seqlock to protect the dentry name, parent, and inode,
  so we can load this tuple atomically, and also check whether any of its
  members have changed.
* Dentry lookups (based on parent, candidate string tuple) recheck the parent
  sequence after the child is found in case anything changed in the parent
  during the path walk.
* inode is also RCU protected so we can load d_inode and use the inode for
  limited things.
* i_mode, i_uid, i_gid can be tested for exec permissions during path walk.
* i_op can be loaded.

When we reach the destination dentry, we lock it, recheck lookup sequence,
and increment its refcount and mountpoint refcount. RCU and vfsmount locks
are dropped. This is termed "dropping rcu-walk". If the dentry refcount does
not match, we can not drop rcu-walk gracefully at the current point in the
lokup, so instead return -ECHILD (for want of a better errno). This signals the
path walking code to re-do the entire lookup with a ref-walk.

Aside from the final dentry, there are other situations that may be encounted
where we cannot continue rcu-walk. In that case, we drop rcu-walk (ie. take
a reference on the last good dentry) and continue with a ref-walk. Again, if
we can drop rcu-walk gracefully, we return -ECHILD and do the whole lookup
using ref-walk. But it is very important that we can continue with ref-walk
for most cases, particularly to avoid the overhead of double lookups, and to
gain the scalability advantages on common path elements (like cwd and root).

The cases where rcu-walk cannot continue are:
* NULL dentry (ie. any uncached path element)
* parent with d_inode->i_op->permission or ACLs
* dentries with d_revalidate
* Following links

In future patches, permission checks and d_revalidate become rcu-walk aware. It
may be possible eventually to make following links rcu-walk aware.

Uncached path elements will always require dropping to ref-walk mode, at the
very least because i_mutex needs to be grabbed, and objects allocated.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Add branch annotations for seqlock read fastpath, and introduce
__read_seqcount_begin and __read_seqcount_end functions, that can avoid the
smp_rmb() if used carefully. These will be used by store-free path walking
algorithm performance is critical and seqlocks are in use.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

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>

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>

dget_locked was a shortcut to avoid the lazy lru manipulation when we already
held dcache_lock (lru manipulation was relatively cheap at that point).
However, how that the lru lock is an innermost one, we never hold it at any
caller, so the lock cost can now be avoided. We already have well working lazy
dcache LRU, so it should be fine to defer LRU manipulations to scan time.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

dcache_lock no longer protects anything. remove it.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

The remaining usages for dcache_lock is to allow atomic, multi-step read-side
operations over the directory tree by excluding modifications to the tree.
Also, to walk in the leaf->root direction in the tree where we don't have
a natural d_lock ordering.

This could be accomplished by taking every d_lock, but this would mean a
huge number of locks and actually gets very tricky.

Solve this instead by using the rename seqlock for multi-step read-side
operations, retry in case of a rename so we don't walk up the wrong parent.
Concurrent dentry insertions are not serialised against.  Concurrent deletes
are tricky when walking up the directory: our parent might have been deleted
when dropping locks so also need to check and retry for that.

We can also use the rename lock in cases where livelock is a worry (and it
is introduced in subsequent patch).
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Add a new lock, dcache_inode_lock, to protect the inode's i_dentry list
from concurrent modification. d_alias is also protected by d_lock.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Protect d_subdirs and d_child with d_lock, except in filesystems that aren't
using dcache_lock for these anyway (eg. using i_mutex).

Note: if we change the locking rule in future so that ->d_child protection is
provided only with ->d_parent->d_lock, it may allow us to reduce some locking.
But it would be an exception to an otherwise regular locking scheme, so we'd
have to see some good results. Probably not worthwhile.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Make d_count non-atomic and protect it with d_lock. This allows us to ensure a
0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when
we start protecting many other dentry members with d_lock.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Add a new lock, dcache_hash_lock, to protect the dcache hash table from
concurrent modification. d_hash is also protected by d_lock.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Remove dcache_lock locking from hostfs filesystem, and move it into dcache
helpers. All that is required is a coherent path name. Protection from
concurrent modification of the namespace after path name generation is not
provided in current code, because dcache_lock is dropped before the path is
used.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Change d_hash so it may be called from lock-free RCU lookups. See similar
patch for d_compare for details.

For in-tree filesystems, this is just a mechanical change.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

Change d_compare so it may be called from lock-free RCU lookups. This
does put significant restrictions on what may be done from the callback,
however there don't seem to have been any problems with in-tree fses.
If some strange use case pops up that _really_ cannot cope with the
rcu-walk rules, we can just add new rcu-unaware callbacks, which would
cause name lookup to drop out of rcu-walk mode.

For in-tree filesystems, this is just a mechanical change.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

smpfs and ncpfs want to update a live dentry name in-place. Rather than
have them open code the locking, provide a documented dcache API.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

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>

Remove redundant (and incorrect, since dcache RCU lookup) dentry locking
documentation and point to the canonical document.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

This is a nasty and error prone API. It is no longer used, remove it.
Signed-off-by: NNick Piggin <npiggin@kernel.dk>

This lets drivers, optionally using the dmaengine, build with DMA_ENGINE
unselected.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

The taskstats structure is internally aligned on 8 byte boundaries but the
layout of the aggregrate reply, with two NLA headers and the pid (each 4
bytes), actually force the entire structure to be unaligned.  This causes
the kernel to issue unaligned access warnings on some architectures like
ia64.  Unfortunately, some software out there doesn't properly unroll the
NLA packet and assumes that the start of the taskstats structure will
always be 20 bytes from the start of the netlink payload.  Aligning the
start of the taskstats structure breaks this software, which we don't
want.  So, for now the alignment only happens on architectures that
require it and those users will have to update to fixed versions of those
packages.  Space is reserved in the packet only when needed.  This ifdef
should be removed in several years e.g.  2012 once we can be confident
that fixed versions are installed on most systems.  We add the padding
before the aggregate since the aggregate is already a defined type.

Commit 85893120 ("delayacct: align to 8 byte boundary on 64-bit systems")
previously addressed the alignment issues by padding out the pid field.
This was supposed to be a compatible change but the circumstances
described above mean that it wasn't.  This patch backs out that change,
since it was a hack, and introduces a new NULL attribute type to provide
the padding.  Padding the response with 4 bytes avoids allocating an
aligned taskstats structure and copying it back.  Since the structure
weighs in at 328 bytes, it's too big to do it on the stack.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reported-by: NBrian Rogers <brian@xyzw.org>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Guillaume Chazarain <guichaz@gmail.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The current packed struct implementation of unaligned access adds the
packed attribute only to the field within the unaligned struct rather than
to the struct as a whole.  This is not sufficient to enforce proper
behaviour on architectures with a default struct alignment of more than
one byte.

For example, the current implementation of __get_unaligned_cpu16 when
compiled for arm with gcc -O1 -mstructure-size-boundary=32 assumes the
struct is on a 4 byte boundary so performs the load of the 16bit packed
field as if it were on a 4 byte boundary:

__get_unaligned_cpu16:
        ldrh    r0, [r0, #0]
        bx      lr

Moving the packed attribute to the struct rather than the field causes the
proper unaligned access code to be generated:

__get_unaligned_cpu16:
	ldrb	r3, [r0, #0]	@ zero_extendqisi2
	ldrb	r0, [r0, #1]	@ zero_extendqisi2
	orr	r0, r3, r0, asl #8
	bx	lr
Signed-off-by: NWill Newton <will.newton@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

spinlock in kthread_worker and wait_queue_head in kthread_work both
should be lockdep sensible, so change the interface to make it
suiltable for CONFIG_LOCKDEP.

tj: comment update
Reported-by: NNicolas <nicolas.mailhot@laposte.net>
Signed-off-by: NYong Zhang <yong.zhang0@gmail.com>
Signed-off-by: NAndy Walls <awalls@md.metrocast.net>
Tested-by: NAndy Walls <awalls@md.metrocast.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NTejun Heo <tj@kernel.org>

The cnt32_to_63 algorithm relies on proper counter data evaluation
ordering to work properly. This was missing from the provided
documentation.

Let's augment the documentation with the missing usage constraint and
fix the only instance that got it wrong.
Signed-off-by: NNicolas Pitre <nico@fluxnic.net>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

$ cat << EOF | gcc -Wconversion -xc -S -o/dev/null -
unsigned f(void) {return NLMSG_HDRLEN;}
EOF
<stdin>: In function 'f':
<stdin>:3:26: warning: negative integer implicitly converted to unsigned type
Signed-off-by: NDmitry V. Levin <ldv@altlinux.org>
Signed-off-by: NKirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This adds arch_remove_reservations(), which an arch can implement if it
needs to protect part of the address space from allocation.

Sometimes that can be done by just putting a region in the resource tree,
but there are cases where that doesn't work well.  For example, x86 BIOS
E820 reservations are not related to devices, so they may overlap part of,
all of, or more than a device resource, so they may not end up at the
correct spot in the resource tree.
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Signed-off-by: NBjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

This reverts commit e7f8567d.
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Signed-off-by: NBjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

For read operation, we have to set the argument _write_ of get_user_pages
to 1 since we will write data to pages. Also, we need to SetPageDirty before
releasing these pages.
Signed-off-by: NHenry C Chang <henry_c_chang@tcloudcomputing.com>
Signed-off-by: NSage Weil <sage@newdream.net>

Implement blk_limits_max_hw_sectors() and make
blk_queue_max_hw_sectors() a wrapper around it.

DM needs this to avoid setting queue_limits' max_hw_sectors and
max_sectors directly.  dm_set_device_limits() now leverages
blk_limits_max_hw_sectors() logic to establish the appropriate
max_hw_sectors minimum (PAGE_SIZE).  Fixes issue where DM was
incorrectly setting max_sectors rather than max_hw_sectors (which
caused dm_merge_bvec()'s max_hw_sectors check to be ineffective).
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Acked-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

When stacking devices, a request_queue is not always available. This
forced us to have a no_cluster flag in the queue_limits that could be
used as a carrier until the request_queue had been set up for a
metadevice.

There were several problems with that approach. First of all it was up
to the stacking device to remember to set queue flag after stacking had
completed. Also, the queue flag and the queue limits had to be kept in
sync at all times. We got that wrong, which could lead to us issuing
commands that went beyond the max scatterlist limit set by the driver.

The proper fix is to avoid having two flags for tracking the same thing.
We deprecate QUEUE_FLAG_CLUSTER and use the queue limit directly in the
block layer merging functions. The queue_limit 'no_cluster' is turned
into 'cluster' to avoid double negatives and to ease stacking.
Clustering defaults to being enabled as before. The queue flag logic is
removed from the stacking function, and explicitly setting the cluster
flag is no longer necessary in DM and MD.
Reported-by: NEd Lin <ed.lin@promise.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Acked-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

The nvram_get function was never in the mainline kernel, it only existed in
an external OpenWrt patch. Use nvram_getenv function, which is in mainline
and use an include instead of an extra function declaration.  et0macaddr
contains the mac address in text from like 00:11:22:33:44:55. We have to
parse it before adding it into macaddr.

nvram_parse_macaddr will be merged into asm/mach-bcm47xx/nvram.h through
the MIPS git tree and will be available soon. It will not build now without
nvram_parse_macaddr, but it hasn't before either.
Signed-off-by: NHauke Mehrtens <hauke@hauke-m.de>
To: linux-mips@linux-mips.org
Cc: mb@bu3sch.de
Cc: netdev@vger.kernel.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: NMichael Buesch <mb@bu3sch.de>
Patchwork: https://patchwork.linux-mips.org/patch/1849/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

There are some situations (e.g. in __pm_generic_call()), where
pm_runtime_suspended() is used to decide whether or not to execute
a device's (system) ->suspend() callback.  The callback is not
executed if pm_runtime_suspended() returns true, but it does so
for devices that don't even support runtime PM, because the
power.disable_depth device field is ignored by it.  This leads to
problems (i.e. devices are not suspened when they should), so rework
pm_runtime_suspended() so that it returns false if the device's
power.disable_depth field is different from zero.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Cc: stable@kernel.org

To implement per event type optional headers we are interested in
knowing how long the metadata structure is.  This patch slits the __u32
version field into a __u8 version and a __u16 metadata_len field (with
__u8 left over).  This should allow for backwards compat ABI.
Signed-off-by: NAlexey Zaytsev <alexey.zaytsev@gmail.com>
[rewrote descrtion and changed object sizes and ordering - eparis]
Signed-off-by: NEric Paris <eparis@redhat.com>