From: Marco Stornelli <marco.stornelli@xxxxxxxxx>
Extended attributes block descriptors tree.
Signed-off-by: Marco Stornelli <marco.stornelli@xxxxxxxxx>
---
diff -Nurp linux-2.6.36-orig/fs/pramfs/desctree.c linux-2.6.36/fs/pramfs/desctree.c
--- linux-2.6.36-orig/fs/pramfs/desctree.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.36/fs/pramfs/desctree.c 2010-11-27 11:12:04.000000000 +0100
@@ -0,0 +1,181 @@
+/*
+ * BRIEF DESCRIPTION
+ *
+ * Extended attributes block descriptors tree.
+ *
+ * Copyright 2010 Marco Stornelli <marco.stornelli@xxxxxxxxx>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/spinlock.h>
+#include "desctree.h"
+#include "pram.h"
+
+/* xblock_desc_init_always()
+ *
+ * These are initializations that need to be done on every
+ * descriptor allocation as the fields are not initialised
+ * by slab allocation.
+ */
+void xblock_desc_init_always(struct pram_xblock_desc *desc)
+{
+ atomic_set(&desc->refcount, 0);
+ desc->blocknr = 0;
+ desc->flags = 0;
+}
+
+/* xblock_desc_init_once()
+ *
+ * These are initializations that only need to be done
+ * once, because the fields are idempotent across use
+ * of the descriptor, so let the slab aware of that.
+ */
+void xblock_desc_init_once(struct pram_xblock_desc *desc)
+{
+ mutex_init(&desc->lock);
+}
+
+/* __insert_xblock_desc()
+ *
+ * Insert a new descriptor in the tree.
+ */
+static void __insert_xblock_desc(struct pram_sb_info *sbi,
+ unsigned long blocknr, struct rb_node *node)
+{
+ struct rb_node **p = &(sbi->desc_tree.rb_node);
+ struct rb_node *parent = NULL;
+ struct pram_xblock_desc *desc;
+
+ while (*p) {
+ parent = *p;
+ desc = rb_entry(parent, struct pram_xblock_desc, node);
+
+ if (blocknr < desc->blocknr)
+ p = &(*p)->rb_left;
+ else if (blocknr > desc->blocknr)
+ p = &(*p)->rb_right;
+ else
+ /* Oops...an other descriptor for the same block ? */
+ BUG();
+ }
+
+ rb_link_node(node, parent, p);
+ rb_insert_color(node, &sbi->desc_tree);
+}
+
+void insert_xblock_desc(struct pram_sb_info *sbi, struct pram_xblock_desc *desc)
+{
+ spin_lock(&sbi->desc_tree_lock);
+ __insert_xblock_desc(sbi, desc->blocknr, &desc->node);
+ spin_unlock(&sbi->desc_tree_lock);
+};
+
+/* __lookup_xblock_desc()
+ *
+ * Search an extended attribute descriptor in the tree via the
+ * block number. It returns the descriptor if it's found or
+ * NULL. If not found it creates a new descriptor if create is not 0.
+ */
+static struct pram_xblock_desc *__lookup_xblock_desc(struct pram_sb_info *sbi,
+ unsigned long blocknr,
+ struct kmem_cache *cache,
+ int create)
+{
+ struct rb_node *n = sbi->desc_tree.rb_node;
+ struct pram_xblock_desc *desc = NULL;
+
+ while (n) {
+ desc = rb_entry(n, struct pram_xblock_desc, node);
+
+ if (blocknr < desc->blocknr)
+ n = n->rb_left;
+ else if (blocknr > desc->blocknr)
+ n = n->rb_right;
+ else {
+ atomic_inc(&desc->refcount);
+ goto out;
+ }
+ }
+
+ /* not found */
+ if (create) {
+ desc = kmem_cache_alloc(cache, GFP_NOFS);
+ if (!desc)
+ return ERR_PTR(-ENOMEM);
+ xblock_desc_init_always(desc);
+ atomic_set(&desc->refcount, 1);
+ desc->blocknr = blocknr;
+ __insert_xblock_desc(sbi, desc->blocknr, &desc->node);
+ }
+out:
+ return desc;
+}
+
+struct pram_xblock_desc *lookup_xblock_desc(struct pram_sb_info *sbi,
+ unsigned long blocknr,
+ struct kmem_cache *cache,
+ int create)
+{
+ struct pram_xblock_desc *desc = NULL;
+
+ spin_lock(&sbi->desc_tree_lock);
+ desc = __lookup_xblock_desc(sbi, blocknr, cache, create);
+ spin_unlock(&sbi->desc_tree_lock);
+ return desc;
+}
+
+/* put_xblock_desc()
+ *
+ * Decrement the reference count and if it reaches zero and the
+ * desciptor has been marked to be free, then we free it.
+ * It returns 0 if the descriptor has been deleted and 1 otherwise.
+ */
+int put_xblock_desc(struct pram_sb_info *sbi, struct pram_xblock_desc *desc)
+{
+ int ret = 1;
+ if (!desc)
+ return ret;
+
+ if (atomic_dec_and_lock(&desc->refcount, &sbi->desc_tree_lock)) {
+ if (test_bit(FREEING, &desc->flags)) {
+ rb_erase(&desc->node, &sbi->desc_tree);
+ pram_dbg("erasing desc for block %lu\n", desc->blocknr);
+ ret = 0;
+ }
+ spin_unlock(&sbi->desc_tree_lock);
+ }
+ return ret;
+};
+
+/* mark_free_desc()
+ *
+ * Mark free a descriptor. The descriptor will be deleted later in the
+ * put_xblock_desc().
+ */
+void mark_free_desc(struct pram_xblock_desc *desc)
+{
+ set_bit(FREEING, &desc->flags);
+}
+
+/* erase_tree()
+ *
+ * Free all objects in the tree.
+ */
+void erase_tree(struct pram_sb_info *sbi, struct kmem_cache *cachep)
+{
+ struct rb_node *n;
+ struct pram_xblock_desc *desc;
+
+ spin_lock(&sbi->desc_tree_lock);
+ n = rb_first(&sbi->desc_tree);
+ while (n) {
+ desc = rb_entry(n, struct pram_xblock_desc, node);
+ rb_erase(n, &sbi->desc_tree);
+ kmem_cache_free(cachep, desc);
+ n = rb_next(n);
+ }
+ spin_unlock(&sbi->desc_tree_lock);
+}
diff -Nurp linux-2.6.36-orig/fs/pramfs/desctree.h linux-2.6.36/fs/pramfs/desctree.h
--- linux-2.6.36-orig/fs/pramfs/desctree.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.36/fs/pramfs/desctree.h 2010-11-27 11:12:10.000000000 +0100
@@ -0,0 +1,44 @@
+/*
+ * BRIEF DESCRIPTION
+ *
+ * Extended attributes block descriptors tree.
+ *
+ * Copyright 2010 Marco Stornelli <marco.stornelli@xxxxxxxxx>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <asm/atomic.h>
+#include <linux/slab.h>
+#include "pram.h"
+
+struct pram_xblock_desc {
+#define FREEING (1UL << 1)
+ unsigned long flags; /* descriptor flags */
+ atomic_t refcount; /* users count of this descriptor */
+ unsigned long blocknr; /* absolute block number */
+ struct mutex lock; /* block lock */
+ struct rb_node node; /* node in the rb tree */
+};
+
+extern struct pram_xblock_desc *lookup_xblock_desc(struct pram_sb_info *sbi,
+ unsigned long blocknr,
+ struct kmem_cache *, int);
+extern void insert_xblock_desc(struct pram_sb_info *sbi,
+ struct pram_xblock_desc *desc);
+extern void mark_free_desc(struct pram_xblock_desc *desc);
+extern int put_xblock_desc(struct pram_sb_info *sbi,
+ struct pram_xblock_desc *desc);
+extern void xblock_desc_init_always(struct pram_xblock_desc *desc);
+extern void xblock_desc_init_once(struct pram_xblock_desc *desc);
+extern void erase_tree(struct pram_sb_info *sbi,
+ struct kmem_cache *);
+
+static inline void xblock_desc_init(struct pram_xblock_desc *desc)
+{
+ xblock_desc_init_always(desc);
+ xblock_desc_init_once(desc);
+};
+
--
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