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xarray: add the xa_lock to the radix_tree_root

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This results in no change in structure size on 64-bit machines as it
fits in the padding between the gfp_t and the void *.  32-bit machines
will grow the structure from 8 to 12 bytes.  Almost all radix trees are
protected with (at least) a spinlock, so as they are converted from
radix trees to xarrays, the data structures will shrink again.

Initialising the spinlock requires a name for the benefit of lockdep, so
RADIX_TREE_INIT() now needs to know the name of the radix tree it's
initialising, and so do IDR_INIT() and IDA_INIT().

Also add the xa_lock() and xa_unlock() family of wrappers to make it
easier to use the lock.  If we could rely on -fplan9-extensions in the
compiler, we could avoid all of this syntactic sugar, but that wasn't
added until gcc 4.6.

Link: http://lkml.kernel.org/r/20180313132639.17387-8-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox
2018-04-10 16:36:52 -07:00
committed by Linus Torvalds
parent e5a9554196
commit f6bb2a2c0b
6 changed files with 42 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/radix-tree.h
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@@ -110,20 +110,23 @@ struct radix_tree_node {
#define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT)
struct radix_tree_root {
spinlock_t xa_lock;
gfp_t gfp_mask;
struct radix_tree_node __rcu *rnode;
};
#define RADIX_TREE_INIT(mask) { \
#define RADIX_TREE_INIT(name, mask) { \
.xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock), \
.gfp_mask = (mask), \
.rnode = NULL, \
}
#define RADIX_TREE(name, mask) \
struct radix_tree_root name = RADIX_TREE_INIT(mask)
struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
#define INIT_RADIX_TREE(root, mask) \
do { \
spin_lock_init(&(root)->xa_lock); \
(root)->gfp_mask = (mask); \
(root)->rnode = NULL; \
} while (0)