The comment states: 'Setting a tag on a not-present item is a BUG.' Hence
if 'index' is larger than the maxindex; the item _cannot_ be presen; it
should also be a BUG.

Also, this allows the following statement (assume a fresh tree):

  radix_tree_tag_set(root, 16, 1);

to fail silently, but when preceded by:

  radix_tree_insert(root, 32, item);

it would BUG, because the height has been extended by the insert.

In neither case was 16 present.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Reduce radix tree node memory usage by about a factor of 4 for small files
(< 64K).  There are pointer traversal and memory usage costs for large
files with dense pagecache.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The ability to have height 0 radix trees (a direct pointer to the data item
rather than going through a full node->slot) quietly disappeared with
old-2.6-bkcvs commit ffee171812d51652f9ba284302d9e5c5cc14bdfd.  On 64-bit
machines this causes nearly 600 bytes to be used for every <= 4K file in
pagecache.

Re-introduce this feature, root tags stored in spare ->gfp_mask bits.

Simplify radix_tree_delete's complex tag clearing arrangement (which would
become even more complex) by just falling back to tag clearing functions
(the pagecache radix-tree never uses this path anyway, so the icache
savings will mean it's actually a speedup).

On my 4GB G5, this saves 8MB RAM per kernel kernel source+object tree in
pagecache.

Pagecache lookup, insertion, and removal speed for small files will also be
improved.

This makes RCU radix tree harder, but it's worth it.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Documentation changes to help radix tree users avoid overrunning the tags
array.  RADIX_TREE_TAGS moves to linux/radix-tree.h and is now known as
RADIX_TREE_MAX_TAGS (Nick Piggin's idea).  Tag parameters are changed to
unsigned, and some comments are updated.
Signed-off-by: NJonathan Corbet <corbet@lwn.net>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

If a tag is set for a node being deleted from a radix_tree, then that
tag gets cleared from the parent of the node, even if it is set for some
siblings of the node begin deleted.

This patch changes the logic to include a test for any_tag_set similar
to the logic a little futher down.  Care is taken to ensure that
'nr_cleared_tags' remains equals to the number of entries in the 'tags'
array which are set to '0' (which means that this tag is not set in the
tree below pathp->node, and should be cleared at pathp->node and
possibly above.

[ Nick says: "Linus FYI, I was able to modify the radix tree test
  harness to catch the bug and can no longer trigger it after the fix.
  Resulting code passes all other harness tests as well of course." ]
Signed-off-by: NNeil Brown <neilb@suse.de>
Acked-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Shrink the height of a radix tree when it is partially truncated - we only do
shrinkage of full truncation at present.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Correctly determine the tags to be cleared in radix_tree_delete() so we
don't keep moving up the tree clearing tags that we don't need to.  For
example, if a tag is simply not set in the deleted item, nor anywhere up
the tree, radix_tree_delete() would attempt to clear it up the entire
height of the tree.

Also, tag_set() was made conditional so as not to dirty too many cachelines
high up in the radix tree.  Instead, put this logic into
radix_tree_tag_set().
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Introduce helper any_tag_set() rather than repeat the same code sequence 4
times.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Reiser4 uses radix trees to solve a trouble reiser4_readdir has serving nfs
requests.

Unfortunately, radix tree api lacks an operation suitable for modifying
existing entry.  This patch adds radix_tree_lookup_slot which returns pointer
to found item within the tree.  That location can be then updated.

Both Nick and Christoph Lameter have patches which need this as well.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

 - added typedef unsigned int __nocast gfp_t;

 - replaced __nocast uses for gfp flags with gfp_t - it gives exactly
   the same warnings as far as sparse is concerned, doesn't change
   generated code (from gcc point of view we replaced unsigned int with
   typedef) and documents what's going on far better.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix the sparse warning "implicit cast to nocast type"
Signed-off-by: NVictor Fusco <victor@cetuc.puc-rio.br>
Signed-off-by: NDomen Puncer <domen@coderock.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Simple patch to radix_tree_tag_get() to return different values for non
present node and tag unset.

The function is not used by any in-kernel callers (yet), but this
information is definitely useful.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

- There is frequent use of indirections in the radix code. This patch
  removes those indirections, makes the code more readable and allows
  the compilers to generate better code.

- Removing indirections allows the removal of several casts.

- Removing indirections allows the reduction of the radix_tree_path
  size from 3 to 2 words.

- Use pathp-> consistently.

- Remove unnecessary tmp variable in radix_tree_insert

- Separate the upper layer processing from the lowest layer in __lookup()
  in order to make it easier to understand what is going on and allow
  compilers to generate better code for the loop.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a new section called ".data.read_mostly" for data items that are read
frequently and rarely written to like cpumaps etc.

If these maps are placed in the .data section then these frequenly read
items may end up in cachelines with data is is frequently updated.  In that
case all processors in an SMP system must needlessly reload the cachelines
again and again containing elements of those frequently used variables.

The ability to share these cachelines will allow each cpu in an SMP system
to keep local copies of those shared cachelines thereby optimizing
performance.
Signed-off-by: NAlok N Kataria <alokk@calsoftinc.com>
Signed-off-by: NShobhit Dayal <shobhit@calsoftinc.com>
Signed-off-by: NChristoph Lameter <christoph@scalex86.org>
Signed-off-by: NShai Fultheim <shai@scalex86.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!