[PATCH] OCFS2: The Second Oracle Cluster Filesystem

The OCFS2 file system module.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>

1 files changed, 544 insertions, 0 deletions

diff --git a/fs/ocfs2/uptodate.c b/fs/ocfs2/uptodate.c
new file mode 100644
index 0000000..3a0458f
--- /dev/null
+++ b/fs/ocfs2/uptodate.c
@@ -0,0 +1,544 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * uptodate.c
+ *
+ * Tracking the up-to-date-ness of a local buffer_head with respect to
+ * the cluster.
+ *
+ * Copyright (C) 2002, 2004, 2005 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ * Standard buffer head caching flags (uptodate, etc) are insufficient
+ * in a clustered environment - a buffer may be marked up to date on
+ * our local node but could have been modified by another cluster
+ * member. As a result an additional (and performant) caching scheme
+ * is required. A further requirement is that we consume as little
+ * memory as possible - we never pin buffer_head structures in order
+ * to cache them.
+ *
+ * We track the existence of up to date buffers on the inodes which
+ * are associated with them. Because we don't want to pin
+ * buffer_heads, this is only a (strong) hint and several other checks
+ * are made in the I/O path to ensure that we don't use a stale or
+ * invalid buffer without going to disk:
+ *	- buffer_jbd is used liberally - if a bh is in the journal on
+ *	  this node then it *must* be up to date.
+ *	- the standard buffer_uptodate() macro is used to detect buffers
+ *	  which may be invalid (even if we have an up to date tracking
+ * 	  item for them)
+ *
+ * For a full understanding of how this code works together, one
+ * should read the callers in dlmglue.c, the I/O functions in
+ * buffer_head_io.c and ocfs2_journal_access in journal.c
+ */
+
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/buffer_head.h>
+#include <linux/rbtree.h>
+#include <linux/jbd.h>
+
+#define MLOG_MASK_PREFIX ML_UPTODATE
+
+#include <cluster/masklog.h>
+
+#include "ocfs2.h"
+
+#include "inode.h"
+#include "uptodate.h"
+
+struct ocfs2_meta_cache_item {
+	struct rb_node	c_node;
+	sector_t	c_block;
+};
+
+static kmem_cache_t *ocfs2_uptodate_cachep = NULL;
+
+void ocfs2_metadata_cache_init(struct inode *inode)
+{
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+	struct ocfs2_caching_info *ci = &oi->ip_metadata_cache;
+
+	oi->ip_flags |= OCFS2_INODE_CACHE_INLINE;
+	ci->ci_num_cached = 0;
+}
+
+/* No lock taken here as 'root' is not expected to be visible to other
+ * processes. */
+static unsigned int ocfs2_purge_copied_metadata_tree(struct rb_root *root)
+{
+	unsigned int purged = 0;
+	struct rb_node *node;
+	struct ocfs2_meta_cache_item *item;
+
+	while ((node = rb_last(root)) != NULL) {
+		item = rb_entry(node, struct ocfs2_meta_cache_item, c_node);
+
+		mlog(0, "Purge item %llu\n",
+		     (unsigned long long) item->c_block);
+
+		rb_erase(&item->c_node, root);
+		kmem_cache_free(ocfs2_uptodate_cachep, item);
+
+		purged++;
+	}
+	return purged;
+}
+
+/* Called from locking and called from ocfs2_clear_inode. Dump the
+ * cache for a given inode.
+ *
+ * This function is a few more lines longer than necessary due to some
+ * accounting done here, but I think it's worth tracking down those
+ * bugs sooner -- Mark */
+void ocfs2_metadata_cache_purge(struct inode *inode)
+{
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+	unsigned int tree, to_purge, purged;
+	struct ocfs2_caching_info *ci = &oi->ip_metadata_cache;
+	struct rb_root root = RB_ROOT;
+
+	spin_lock(&oi->ip_lock);
+	tree = !(oi->ip_flags & OCFS2_INODE_CACHE_INLINE);
+	to_purge = ci->ci_num_cached;
+
+	mlog(0, "Purge %u %s items from Inode %"MLFu64"\n", to_purge,
+	     tree ? "array" : "tree", oi->ip_blkno);
+
+	/* If we're a tree, save off the root so that we can safely
+	 * initialize the cache. We do the work to free tree members
+	 * without the spinlock. */
+	if (tree)
+		root = ci->ci_cache.ci_tree;
+
+	ocfs2_metadata_cache_init(inode);
+	spin_unlock(&oi->ip_lock);
+
+	purged = ocfs2_purge_copied_metadata_tree(&root);
+	/* If possible, track the number wiped so that we can more
+	 * easily detect counting errors. Unfortunately, this is only
+	 * meaningful for trees. */
+	if (tree && purged != to_purge)
+		mlog(ML_ERROR, "Inode %"MLFu64", count = %u, purged = %u\n",
+		     oi->ip_blkno, to_purge, purged);
+}
+
+/* Returns the index in the cache array, -1 if not found.
+ * Requires ip_lock. */
+static int ocfs2_search_cache_array(struct ocfs2_caching_info *ci,
+				    sector_t item)
+{
+	int i;
+
+	for (i = 0; i < ci->ci_num_cached; i++) {
+		if (item == ci->ci_cache.ci_array[i])
+			return i;
+	}
+
+	return -1;
+}
+
+/* Returns the cache item if found, otherwise NULL.
+ * Requires ip_lock. */
+static struct ocfs2_meta_cache_item *
+ocfs2_search_cache_tree(struct ocfs2_caching_info *ci,
+			sector_t block)
+{
+	struct rb_node * n = ci->ci_cache.ci_tree.rb_node;
+	struct ocfs2_meta_cache_item *item = NULL;
+
+	while (n) {
+		item = rb_entry(n, struct ocfs2_meta_cache_item, c_node);
+
+		if (block < item->c_block)
+			n = n->rb_left;
+		else if (block > item->c_block)
+			n = n->rb_right;
+		else
+			return item;
+	}
+
+	return NULL;
+}
+
+static int ocfs2_buffer_cached(struct ocfs2_inode_info *oi,
+			       struct buffer_head *bh)
+{
+	int index = -1;
+	struct ocfs2_meta_cache_item *item = NULL;
+
+	spin_lock(&oi->ip_lock);
+
+	mlog(0, "Inode %"MLFu64", query block %llu (inline = %u)\n",
+	     oi->ip_blkno, (unsigned long long) bh->b_blocknr,
+	     !!(oi->ip_flags & OCFS2_INODE_CACHE_INLINE));
+
+	if (oi->ip_flags & OCFS2_INODE_CACHE_INLINE)
+		index = ocfs2_search_cache_array(&oi->ip_metadata_cache,
+						 bh->b_blocknr);
+	else
+		item = ocfs2_search_cache_tree(&oi->ip_metadata_cache,
+					       bh->b_blocknr);
+
+	spin_unlock(&oi->ip_lock);
+
+	mlog(0, "index = %d, item = %p\n", index, item);
+
+	return (index != -1) || (item != NULL);
+}
+
+/* Warning: even if it returns true, this does *not* guarantee that
+ * the block is stored in our inode metadata cache. */
+int ocfs2_buffer_uptodate(struct inode *inode,
+			  struct buffer_head *bh)
+{
+	/* Doesn't matter if the bh is in our cache or not -- if it's
+	 * not marked uptodate then we know it can't have correct
+	 * data. */
+	if (!buffer_uptodate(bh))
+		return 0;
+
+	/* OCFS2 does not allow multiple nodes to be changing the same
+	 * block at the same time. */
+	if (buffer_jbd(bh))
+		return 1;
+
+	/* Ok, locally the buffer is marked as up to date, now search
+	 * our cache to see if we can trust that. */
+	return ocfs2_buffer_cached(OCFS2_I(inode), bh);
+}
+
+/* Requires ip_lock */
+static void ocfs2_append_cache_array(struct ocfs2_caching_info *ci,
+				     sector_t block)
+{
+	BUG_ON(ci->ci_num_cached >= OCFS2_INODE_MAX_CACHE_ARRAY);
+
+	mlog(0, "block %llu takes position %u\n", (unsigned long long) block,
+	     ci->ci_num_cached);
+
+	ci->ci_cache.ci_array[ci->ci_num_cached] = block;
+	ci->ci_num_cached++;
+}
+
+/* By now the caller should have checked that the item does *not*
+ * exist in the tree.
+ * Requires ip_lock. */
+static void __ocfs2_insert_cache_tree(struct ocfs2_caching_info *ci,
+				      struct ocfs2_meta_cache_item *new)
+{
+	sector_t block = new->c_block;
+	struct rb_node *parent = NULL;
+	struct rb_node **p = &ci->ci_cache.ci_tree.rb_node;
+	struct ocfs2_meta_cache_item *tmp;
+
+	mlog(0, "Insert block %llu num = %u\n", (unsigned long long) block,
+	     ci->ci_num_cached);
+
+	while(*p) {
+		parent = *p;
+
+		tmp = rb_entry(parent, struct ocfs2_meta_cache_item, c_node);
+
+		if (block < tmp->c_block)
+			p = &(*p)->rb_left;
+		else if (block > tmp->c_block)
+			p = &(*p)->rb_right;
+		else {
+			/* This should never happen! */
+			mlog(ML_ERROR, "Duplicate block %llu cached!\n",
+			     (unsigned long long) block);
+			BUG();
+		}
+	}
+
+	rb_link_node(&new->c_node, parent, p);
+	rb_insert_color(&new->c_node, &ci->ci_cache.ci_tree);
+	ci->ci_num_cached++;
+}
+
+static inline int ocfs2_insert_can_use_array(struct ocfs2_inode_info *oi,
+					     struct ocfs2_caching_info *ci)
+{
+	assert_spin_locked(&oi->ip_lock);
+
+	return (oi->ip_flags & OCFS2_INODE_CACHE_INLINE) &&
+		(ci->ci_num_cached < OCFS2_INODE_MAX_CACHE_ARRAY);
+}
+
+/* tree should be exactly OCFS2_INODE_MAX_CACHE_ARRAY wide. NULL the
+ * pointers in tree after we use them - this allows caller to detect
+ * when to free in case of error. */
+static void ocfs2_expand_cache(struct ocfs2_inode_info *oi,
+			       struct ocfs2_meta_cache_item **tree)
+{
+	int i;
+	struct ocfs2_caching_info *ci = &oi->ip_metadata_cache;
+
+	mlog_bug_on_msg(ci->ci_num_cached != OCFS2_INODE_MAX_CACHE_ARRAY,
+			"Inode %"MLFu64", num cached = %u, should be %u\n",
+			oi->ip_blkno, ci->ci_num_cached,
+			OCFS2_INODE_MAX_CACHE_ARRAY);
+	mlog_bug_on_msg(!(oi->ip_flags & OCFS2_INODE_CACHE_INLINE),
+			"Inode %"MLFu64" not marked as inline anymore!\n",
+			oi->ip_blkno);
+	assert_spin_locked(&oi->ip_lock);
+
+	/* Be careful to initialize the tree members *first* because
+	 * once the ci_tree is used, the array is junk... */
+	for(i = 0; i < OCFS2_INODE_MAX_CACHE_ARRAY; i++)
+		tree[i]->c_block = ci->ci_cache.ci_array[i];
+
+	oi->ip_flags &= ~OCFS2_INODE_CACHE_INLINE;
+	ci->ci_cache.ci_tree = RB_ROOT;
+	/* this will be set again by __ocfs2_insert_cache_tree */
+	ci->ci_num_cached = 0;
+
+	for(i = 0; i < OCFS2_INODE_MAX_CACHE_ARRAY; i++) {
+		__ocfs2_insert_cache_tree(ci, tree[i]);
+		tree[i] = NULL;
+	}
+
+	mlog(0, "Expanded %"MLFu64" to a tree cache: flags 0x%x, num = %u\n",
+	     oi->ip_blkno, oi->ip_flags, ci->ci_num_cached);
+}
+
+/* Slow path function - memory allocation is necessary. See the
+ * comment above ocfs2_set_buffer_uptodate for more information. */
+static void __ocfs2_set_buffer_uptodate(struct ocfs2_inode_info *oi,
+					sector_t block,
+					int expand_tree)
+{
+	int i;
+	struct ocfs2_caching_info *ci = &oi->ip_metadata_cache;
+	struct ocfs2_meta_cache_item *new = NULL;
+	struct ocfs2_meta_cache_item *tree[OCFS2_INODE_MAX_CACHE_ARRAY] =
+		{ NULL, };
+
+	mlog(0, "Inode %"MLFu64", block %llu, expand = %d\n",
+	     oi->ip_blkno, (unsigned long long) block, expand_tree);
+
+	new = kmem_cache_alloc(ocfs2_uptodate_cachep, GFP_KERNEL);
+	if (!new) {
+		mlog_errno(-ENOMEM);
+		return;
+	}
+	new->c_block = block;
+
+	if (expand_tree) {
+		/* Do *not* allocate an array here - the removal code
+		 * has no way of tracking that. */
+		for(i = 0; i < OCFS2_INODE_MAX_CACHE_ARRAY; i++) {
+			tree[i] = kmem_cache_alloc(ocfs2_uptodate_cachep,
+						   GFP_KERNEL);
+			if (!tree[i]) {
+				mlog_errno(-ENOMEM);
+				goto out_free;
+			}
+
+			/* These are initialized in ocfs2_expand_cache! */
+		}
+	}
+
+	spin_lock(&oi->ip_lock);
+	if (ocfs2_insert_can_use_array(oi, ci)) {
+		mlog(0, "Someone cleared the tree underneath us\n");
+		/* Ok, items were removed from the cache in between
+		 * locks. Detect this and revert back to the fast path */
+		ocfs2_append_cache_array(ci, block);
+		spin_unlock(&oi->ip_lock);
+		goto out_free;
+	}
+
+	if (expand_tree)
+		ocfs2_expand_cache(oi, tree);
+
+	__ocfs2_insert_cache_tree(ci, new);
+	spin_unlock(&oi->ip_lock);
+
+	new = NULL;
+out_free:
+	if (new)
+		kmem_cache_free(ocfs2_uptodate_cachep, new);
+
+	/* If these were used, then ocfs2_expand_cache re-set them to
+	 * NULL for us. */
+	if (tree[0]) {
+		for(i = 0; i < OCFS2_INODE_MAX_CACHE_ARRAY; i++)
+			if (tree[i])
+				kmem_cache_free(ocfs2_uptodate_cachep,
+						tree[i]);
+	}
+}
+
+/* Item insertion is guarded by ip_io_sem, so the insertion path takes
+ * advantage of this by not rechecking for a duplicate insert during
+ * the slow case. Additionally, if the cache needs to be bumped up to
+ * a tree, the code will not recheck after acquiring the lock --
+ * multiple paths cannot be expanding to a tree at the same time.
+ *
+ * The slow path takes into account that items can be removed
+ * (including the whole tree wiped and reset) when this process it out
+ * allocating memory. In those cases, it reverts back to the fast
+ * path.
+ *
+ * Note that this function may actually fail to insert the block if
+ * memory cannot be allocated. This is not fatal however (but may
+ * result in a performance penalty) */
+void ocfs2_set_buffer_uptodate(struct inode *inode,
+			       struct buffer_head *bh)
+{
+	int expand;
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+	struct ocfs2_caching_info *ci = &oi->ip_metadata_cache;
+
+	/* The block may very well exist in our cache already, so avoid
+	 * doing any more work in that case. */
+	if (ocfs2_buffer_cached(oi, bh))
+		return;
+
+	mlog(0, "Inode %"MLFu64", inserting block %llu\n", oi->ip_blkno,
+	     (unsigned long long) bh->b_blocknr);
+
+	/* No need to recheck under spinlock - insertion is guarded by
+	 * ip_io_sem */
+	spin_lock(&oi->ip_lock);
+	if (ocfs2_insert_can_use_array(oi, ci)) {
+		/* Fast case - it's an array and there's a free
+		 * spot. */
+		ocfs2_append_cache_array(ci, bh->b_blocknr);
+		spin_unlock(&oi->ip_lock);
+		return;
+	}
+
+	expand = 0;
+	if (oi->ip_flags & OCFS2_INODE_CACHE_INLINE) {
+		/* We need to bump things up to a tree. */
+		expand = 1;
+	}
+	spin_unlock(&oi->ip_lock);
+
+	__ocfs2_set_buffer_uptodate(oi, bh->b_blocknr, expand);
+}
+
+/* Called against a newly allocated buffer. Most likely nobody should
+ * be able to read this sort of metadata while it's still being
+ * allocated, but this is careful to take ip_io_sem anyway. */
+void ocfs2_set_new_buffer_uptodate(struct inode *inode,
+				   struct buffer_head *bh)
+{
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+
+	/* This should definitely *not* exist in our cache */
+	BUG_ON(ocfs2_buffer_cached(oi, bh));
+
+	set_buffer_uptodate(bh);
+
+	down(&oi->ip_io_sem);
+	ocfs2_set_buffer_uptodate(inode, bh);
+	up(&oi->ip_io_sem);
+}
+
+/* Requires ip_lock. */
+static void ocfs2_remove_metadata_array(struct ocfs2_caching_info *ci,
+					int index)
+{
+	sector_t *array = ci->ci_cache.ci_array;
+	int bytes;
+
+	BUG_ON(index < 0 || index >= OCFS2_INODE_MAX_CACHE_ARRAY);
+	BUG_ON(index >= ci->ci_num_cached);
+	BUG_ON(!ci->ci_num_cached);
+
+	mlog(0, "remove index %d (num_cached = %u\n", index,
+	     ci->ci_num_cached);
+
+	ci->ci_num_cached--;
+
+	/* don't need to copy if the array is now empty, or if we
+	 * removed at the tail */
+	if (ci->ci_num_cached && index < ci->ci_num_cached) {
+		bytes = sizeof(sector_t) * (ci->ci_num_cached - index);
+		memmove(&array[index], &array[index + 1], bytes);
+	}
+}
+
+/* Requires ip_lock. */
+static void ocfs2_remove_metadata_tree(struct ocfs2_caching_info *ci,
+				       struct ocfs2_meta_cache_item *item)
+{
+	mlog(0, "remove block %llu from tree\n",
+	     (unsigned long long) item->c_block);
+
+	rb_erase(&item->c_node, &ci->ci_cache.ci_tree);
+	ci->ci_num_cached--;
+}
+
+/* Called when we remove a chunk of metadata from an inode. We don't
+ * bother reverting things to an inlined array in the case of a remove
+ * which moves us back under the limit. */
+void ocfs2_remove_from_cache(struct inode *inode,
+			     struct buffer_head *bh)
+{
+	int index;
+	sector_t block = bh->b_blocknr;
+	struct ocfs2_meta_cache_item *item = NULL;
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+	struct ocfs2_caching_info *ci = &oi->ip_metadata_cache;
+
+	spin_lock(&oi->ip_lock);
+	mlog(0, "Inode %"MLFu64", remove %llu, items = %u, array = %u\n",
+	     oi->ip_blkno, (unsigned long long) block, ci->ci_num_cached,
+	     oi->ip_flags & OCFS2_INODE_CACHE_INLINE);
+
+	if (oi->ip_flags & OCFS2_INODE_CACHE_INLINE) {
+		index = ocfs2_search_cache_array(ci, block);
+		if (index != -1)
+			ocfs2_remove_metadata_array(ci, index);
+	} else {
+		item = ocfs2_search_cache_tree(ci, block);
+		if (item)
+			ocfs2_remove_metadata_tree(ci, item);
+	}
+	spin_unlock(&oi->ip_lock);
+
+	if (item)
+		kmem_cache_free(ocfs2_uptodate_cachep, item);
+}
+
+int __init init_ocfs2_uptodate_cache(void)
+{
+	ocfs2_uptodate_cachep = kmem_cache_create("ocfs2_uptodate",
+				  sizeof(struct ocfs2_meta_cache_item),
+				  0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (!ocfs2_uptodate_cachep)
+		return -ENOMEM;
+
+	mlog(0, "%u inlined cache items per inode.\n",
+	     OCFS2_INODE_MAX_CACHE_ARRAY);
+
+	return 0;
+}
+
+void __exit exit_ocfs2_uptodate_cache(void)
+{
+	if (ocfs2_uptodate_cachep)
+		kmem_cache_destroy(ocfs2_uptodate_cachep);
+}