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Subject[PATCH v9 07/61] xarray: Add the xa_lock to the radix_tree_root
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

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.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
---
fs/f2fs/gc.c | 2 +-
include/linux/idr.h | 19 ++++++++++---------
include/linux/radix-tree.h | 7 +++++--
include/linux/xarray.h | 24 ++++++++++++++++++++++++
kernel/pid.c | 2 +-
tools/include/linux/spinlock.h | 1 +
6 files changed, 42 insertions(+), 13 deletions(-)
create mode 100644 include/linux/xarray.h

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index aa720cc44509..7aa15134180e 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1006,7 +1006,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
unsigned int init_segno = segno;
struct gc_inode_list gc_list = {
.ilist = LIST_HEAD_INIT(gc_list.ilist),
- .iroot = RADIX_TREE_INIT(GFP_NOFS),
+ .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
};

trace_f2fs_gc_begin(sbi->sb, sync, background,
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 913c335054f0..e856f4e0ab35 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -32,27 +32,28 @@ struct idr {
#define IDR_RT_MARKER (ROOT_IS_IDR | (__force gfp_t) \
(1 << (ROOT_TAG_SHIFT + IDR_FREE)))

-#define IDR_INIT_BASE(base) { \
- .idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER), \
+#define IDR_INIT_BASE(name, base) { \
+ .idr_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER), \
.idr_base = (base), \
.idr_next = 0, \
}

/**
* IDR_INIT() - Initialise an IDR.
+ * @name: Name of IDR.
*
* A freshly-initialised IDR contains no IDs.
*/
-#define IDR_INIT IDR_INIT_BASE(0)
+#define IDR_INIT(name) IDR_INIT_BASE(name, 0)

/**
- * DEFINE_IDR() - Define a statically-allocated IDR
- * @name: Name of IDR
+ * DEFINE_IDR() - Define a statically-allocated IDR.
+ * @name: Name of IDR.
*
* An IDR defined using this macro is ready for use with no additional
* initialisation required. It contains no IDs.
*/
-#define DEFINE_IDR(name) struct idr name = IDR_INIT
+#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)

/**
* idr_get_cursor - Return the current position of the cyclic allocator
@@ -219,10 +220,10 @@ struct ida {
struct radix_tree_root ida_rt;
};

-#define IDA_INIT { \
- .ida_rt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT), \
+#define IDA_INIT(name) { \
+ .ida_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER | GFP_NOWAIT), \
}
-#define DEFINE_IDA(name) struct ida name = IDA_INIT
+#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)

int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 6c4e2e716dac..34149e8b5f73 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -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)
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
new file mode 100644
index 000000000000..2dfc8006fe64
--- /dev/null
+++ b/include/linux/xarray.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+#ifndef _LINUX_XARRAY_H
+#define _LINUX_XARRAY_H
+/*
+ * eXtensible Arrays
+ * Copyright (c) 2017 Microsoft Corporation
+ * Author: Matthew Wilcox <mawilcox@microsoft.com>
+ */
+
+#include <linux/spinlock.h>
+
+#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
+#define xa_lock(xa) spin_lock(&(xa)->xa_lock)
+#define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)
+#define xa_lock_bh(xa) spin_lock_bh(&(xa)->xa_lock)
+#define xa_unlock_bh(xa) spin_unlock_bh(&(xa)->xa_lock)
+#define xa_lock_irq(xa) spin_lock_irq(&(xa)->xa_lock)
+#define xa_unlock_irq(xa) spin_unlock_irq(&(xa)->xa_lock)
+#define xa_lock_irqsave(xa, flags) \
+ spin_lock_irqsave(&(xa)->xa_lock, flags)
+#define xa_unlock_irqrestore(xa, flags) \
+ spin_unlock_irqrestore(&(xa)->xa_lock, flags)
+
+#endif /* _LINUX_XARRAY_H */
diff --git a/kernel/pid.c b/kernel/pid.c
index ed6c343fe50d..157fe4b19971 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -70,7 +70,7 @@ int pid_max_max = PID_MAX_LIMIT;
*/
struct pid_namespace init_pid_ns = {
.kref = KREF_INIT(2),
- .idr = IDR_INIT,
+ .idr = IDR_INIT(init_pid_ns.idr),
.pid_allocated = PIDNS_ADDING,
.level = 0,
.child_reaper = &init_task,
diff --git a/tools/include/linux/spinlock.h b/tools/include/linux/spinlock.h
index 4ed569fcb139..b21b586b9854 100644
--- a/tools/include/linux/spinlock.h
+++ b/tools/include/linux/spinlock.h
@@ -7,6 +7,7 @@

#define spinlock_t pthread_mutex_t
#define DEFINE_SPINLOCK(x) pthread_mutex_t x = PTHREAD_MUTEX_INITIALIZER;
+#define __SPIN_LOCK_UNLOCKED(x) (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER

#define spin_lock_irqsave(x, f) (void)f, pthread_mutex_lock(x)
#define spin_unlock_irqrestore(x, f) (void)f, pthread_mutex_unlock(x)
--
2.16.1
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