lib/generic-radix-tree.c: Make nodes more reasonably sized

this code originally used the page allocator directly, but most code
shouldn't do that - PAGE_SIZE varies with architecture, and slab is
faster.

4k is also on the large side for typical usage, 512 bytes is a better
choice for typical usage that might be somewhat sparse.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

lib/generic-radix-tree.c: Add peek_prev()

This patch adds genradix_peek_prev(), genradix_iter_rewind(), and
genradix_for_each_reverse(), for iterating backwards over a generic
radix tree.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

lib/generic-radix-tree.c: Don't overflow in peek()

When we started spreading new inode numbers throughout most of the 64
bit inode space, that triggered some corner case bugs, in particular
some integer overflows related to the radix tree code. Oops.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

lib/generic-radix-tree.c: add kmemleak annotations

Kmemleak is falsely reporting a leak of the slab allocation in
sctp_stream_init_ext():

BUG: memory leak
unreferenced object 0xffff8881114f5d80 (size 96):
comm "syz-executor934", pid 7160, jiffies 4294993058 (age 31.950s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000ce7a1326>] kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]
[<00000000ce7a1326>] slab_post_alloc_hook mm/slab.h:439 [inline]
[<00000000ce7a1326>] slab_alloc mm/slab.c:3326 [inline]
[<00000000ce7a1326>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553
[<000000007abb7ac9>] kmalloc include/linux/slab.h:547 [inline]
[<000000007abb7ac9>] kzalloc include/linux/slab.h:742 [inline]
[<000000007abb7ac9>] sctp_stream_init_ext+0x2b/0xa0 net/sctp/stream.c:157
[<0000000048ecb9c1>] sctp_sendmsg_to_asoc+0x946/0xa00 net/sctp/socket.c:1882
[<000000004483ca2b>] sctp_sendmsg+0x2a8/0x990 net/sctp/socket.c:2102
[...]

But it's freed later. Kmemleak misses the allocation because its
pointer is stored in the generic radix tree sctp_stream::out, and the
generic radix tree uses raw pages which aren't tracked by kmemleak.

Fix this by adding the kmemleak hooks to the generic radix tree code.

Link: http://lkml.kernel.org/r/20191004065039.727564-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reported-by: <syzbot+7f3b6b106be8dcdcdeec@syzkaller.appspotmail.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/generic-radix-tree.c: make 2 functions static inline

When building with W=1, we get some warnings:

l CC lib/generic-radix-tree.o
lib/generic-radix-tree.c:39:10: warning: no previous prototype for 'genradix_root_to_depth' [-Wmissing-prototypes]
39 | unsigned genradix_root_to_depth(struct genradix_root *r)
| ^~~~~~~~~~~~~~~~~~~~~~
lib/generic-radix-tree.c:44:23: warning: no previous prototype for 'genradix_root_to_node' [-Wmissing-prototypes]
44 | struct genradix_node *genradix_root_to_node(struct genradix_root *r)
| ^~~~~~~~~~~~~~~~~~~~~

They're not used anywhere else, so make them static inline.

Link: http://lkml.kernel.org/r/46923.1565236485@turing-police
Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

generic radix trees

Very simple radix tree implementation that supports storing arbitrary
size entries, up to PAGE_SIZE - upcoming patches will convert existing
flex_array users to genradixes. The new genradix code has a much
simpler API and implementation, and doesn't have a hard limit on the
number of elements like flex_array does.

Link: http://lkml.kernel.org/r/20181217131929.11727-5-kent.overstreet@gmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pravin B Shelar <pshelar@ovn.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>