/* -*- 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 <cluster/masklog.h>
  
  #include "ocfs2.h"
  
  #include "inode.h"
  #include "uptodate.h"
  #include "ocfs2_trace.h"
  
  struct ocfs2_meta_cache_item {
  	struct rb_node	c_node;
  	sector_t	c_block;
  };
  
  static struct kmem_cache *ocfs2_uptodate_cachep = NULL;
  
  u64 ocfs2_metadata_cache_owner(struct ocfs2_caching_info *ci)
  {
  	BUG_ON(!ci || !ci->ci_ops);
  
  	return ci->ci_ops->co_owner(ci);
  }
  
  struct super_block *ocfs2_metadata_cache_get_super(struct ocfs2_caching_info *ci)
  {
  	BUG_ON(!ci || !ci->ci_ops);
  
  	return ci->ci_ops->co_get_super(ci);
  }
  
  static void ocfs2_metadata_cache_lock(struct ocfs2_caching_info *ci)
  {
  	BUG_ON(!ci || !ci->ci_ops);
  
  	ci->ci_ops->co_cache_lock(ci);
  }
  
  static void ocfs2_metadata_cache_unlock(struct ocfs2_caching_info *ci)
  {
  	BUG_ON(!ci || !ci->ci_ops);
  
  	ci->ci_ops->co_cache_unlock(ci);
  }
  
  void ocfs2_metadata_cache_io_lock(struct ocfs2_caching_info *ci)
  {
  	BUG_ON(!ci || !ci->ci_ops);
  
  	ci->ci_ops->co_io_lock(ci);
  }
  
  void ocfs2_metadata_cache_io_unlock(struct ocfs2_caching_info *ci)
  {
  	BUG_ON(!ci || !ci->ci_ops);
  
  	ci->ci_ops->co_io_unlock(ci);
  }
  
  
  static void ocfs2_metadata_cache_reset(struct ocfs2_caching_info *ci,
  				       int clear)
  {
  	ci->ci_flags |= OCFS2_CACHE_FL_INLINE;
  	ci->ci_num_cached = 0;
  
  	if (clear) {
  		ci->ci_created_trans = 0;
  		ci->ci_last_trans = 0;
  	}
  }
  
  void ocfs2_metadata_cache_init(struct ocfs2_caching_info *ci,
  			       const struct ocfs2_caching_operations *ops)
  {
  	BUG_ON(!ops);
  
  	ci->ci_ops = ops;
  	ocfs2_metadata_cache_reset(ci, 1);
  }
  
  void ocfs2_metadata_cache_exit(struct ocfs2_caching_info *ci)
  {
  	ocfs2_metadata_cache_purge(ci);
  	ocfs2_metadata_cache_reset(ci, 1);
  }
  
  
  /* 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);
  
  		trace_ocfs2_purge_copied_metadata_tree(
  					(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 ocfs2_caching_info *ci)
  {
  	unsigned int tree, to_purge, purged;
  	struct rb_root root = RB_ROOT;
  
  	BUG_ON(!ci || !ci->ci_ops);
  
  	ocfs2_metadata_cache_lock(ci);
  	tree = !(ci->ci_flags & OCFS2_CACHE_FL_INLINE);
  	to_purge = ci->ci_num_cached;
  
  	trace_ocfs2_metadata_cache_purge(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		to_purge, tree);
  
  	/* 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_reset(ci, 0);
  	ocfs2_metadata_cache_unlock(ci);
  
  	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, "Owner %llu, count = %u, purged = %u
  ",
  		     (unsigned long long)ocfs2_metadata_cache_owner(ci),
  		     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_caching_info *ci,
  			       struct buffer_head *bh)
  {
  	int index = -1;
  	struct ocfs2_meta_cache_item *item = NULL;
  
  	ocfs2_metadata_cache_lock(ci);
  
  	trace_ocfs2_buffer_cached_begin(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(unsigned long long) bh->b_blocknr,
  		!!(ci->ci_flags & OCFS2_CACHE_FL_INLINE));
  
  	if (ci->ci_flags & OCFS2_CACHE_FL_INLINE)
  		index = ocfs2_search_cache_array(ci, bh->b_blocknr);
  	else
  		item = ocfs2_search_cache_tree(ci, bh->b_blocknr);
  
  	ocfs2_metadata_cache_unlock(ci);
  
  	trace_ocfs2_buffer_cached_end(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.
   *
   * This can be called under lock_buffer()
   */
  int ocfs2_buffer_uptodate(struct ocfs2_caching_info *ci,
  			  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(ci, bh);
  }
  
  /*
   * Determine whether a buffer is currently out on a read-ahead request.
   * ci_io_sem should be held to serialize submitters with the logic here.
   */
  int ocfs2_buffer_read_ahead(struct ocfs2_caching_info *ci,
  			    struct buffer_head *bh)
  {
  	return buffer_locked(bh) && ocfs2_buffer_cached(ci, 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_CACHE_INFO_MAX_ARRAY);
  
  	trace_ocfs2_append_cache_array(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(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;
  
  	trace_ocfs2_insert_cache_tree(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(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!
  ",
  			     (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++;
  }
  
  /* co_cache_lock() must be held */
  static inline int ocfs2_insert_can_use_array(struct ocfs2_caching_info *ci)
  {
  	return (ci->ci_flags & OCFS2_CACHE_FL_INLINE) &&
  		(ci->ci_num_cached < OCFS2_CACHE_INFO_MAX_ARRAY);
  }
  
  /* tree should be exactly OCFS2_CACHE_INFO_MAX_ARRAY wide. NULL the
   * pointers in tree after we use them - this allows caller to detect
   * when to free in case of error.
   *
   * The co_cache_lock() must be held. */
  static void ocfs2_expand_cache(struct ocfs2_caching_info *ci,
  			       struct ocfs2_meta_cache_item **tree)
  {
  	int i;
  
  	mlog_bug_on_msg(ci->ci_num_cached != OCFS2_CACHE_INFO_MAX_ARRAY,
  			"Owner %llu, num cached = %u, should be %u
  ",
  			(unsigned long long)ocfs2_metadata_cache_owner(ci),
  			ci->ci_num_cached, OCFS2_CACHE_INFO_MAX_ARRAY);
  	mlog_bug_on_msg(!(ci->ci_flags & OCFS2_CACHE_FL_INLINE),
  			"Owner %llu not marked as inline anymore!
  ",
  			(unsigned long long)ocfs2_metadata_cache_owner(ci));
  
  	/* Be careful to initialize the tree members *first* because
  	 * once the ci_tree is used, the array is junk... */
  	for (i = 0; i < OCFS2_CACHE_INFO_MAX_ARRAY; i++)
  		tree[i]->c_block = ci->ci_cache.ci_array[i];
  
  	ci->ci_flags &= ~OCFS2_CACHE_FL_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_CACHE_INFO_MAX_ARRAY; i++) {
  		__ocfs2_insert_cache_tree(ci, tree[i]);
  		tree[i] = NULL;
  	}
  
  	trace_ocfs2_expand_cache(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		ci->ci_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_caching_info *ci,
  					sector_t block,
  					int expand_tree)
  {
  	int i;
  	struct ocfs2_meta_cache_item *new = NULL;
  	struct ocfs2_meta_cache_item *tree[OCFS2_CACHE_INFO_MAX_ARRAY] =
  		{ NULL, };
  
  	trace_ocfs2_set_buffer_uptodate(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(unsigned long long)block, expand_tree);
  
  	new = kmem_cache_alloc(ocfs2_uptodate_cachep, GFP_NOFS);
  	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_CACHE_INFO_MAX_ARRAY; i++) {
  			tree[i] = kmem_cache_alloc(ocfs2_uptodate_cachep,
  						   GFP_NOFS);
  			if (!tree[i]) {
  				mlog_errno(-ENOMEM);
  				goto out_free;
  			}
  
  			/* These are initialized in ocfs2_expand_cache! */
  		}
  	}
  
  	ocfs2_metadata_cache_lock(ci);
  	if (ocfs2_insert_can_use_array(ci)) {
  		/* 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);
  		ocfs2_metadata_cache_unlock(ci);
  		goto out_free;
  	}
  
  	if (expand_tree)
  		ocfs2_expand_cache(ci, tree);
  
  	__ocfs2_insert_cache_tree(ci, new);
  	ocfs2_metadata_cache_unlock(ci);
  
  	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_CACHE_INFO_MAX_ARRAY; i++)
  			if (tree[i])
  				kmem_cache_free(ocfs2_uptodate_cachep,
  						tree[i]);
  	}
  }
  
  /* Item insertion is guarded by co_io_lock(), 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)
   *
   * Readahead buffers can be passed in here before the I/O request is
   * completed.
   */
  void ocfs2_set_buffer_uptodate(struct ocfs2_caching_info *ci,
  			       struct buffer_head *bh)
  {
  	int expand;
  
  	/* The block may very well exist in our cache already, so avoid
  	 * doing any more work in that case. */
  	if (ocfs2_buffer_cached(ci, bh))
  		return;
  
  	trace_ocfs2_set_buffer_uptodate_begin(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(unsigned long long)bh->b_blocknr);
  
  	/* No need to recheck under spinlock - insertion is guarded by
  	 * co_io_lock() */
  	ocfs2_metadata_cache_lock(ci);
  	if (ocfs2_insert_can_use_array(ci)) {
  		/* Fast case - it's an array and there's a free
  		 * spot. */
  		ocfs2_append_cache_array(ci, bh->b_blocknr);
  		ocfs2_metadata_cache_unlock(ci);
  		return;
  	}
  
  	expand = 0;
  	if (ci->ci_flags & OCFS2_CACHE_FL_INLINE) {
  		/* We need to bump things up to a tree. */
  		expand = 1;
  	}
  	ocfs2_metadata_cache_unlock(ci);
  
  	__ocfs2_set_buffer_uptodate(ci, 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 co_io_lock() anyway. */
  void ocfs2_set_new_buffer_uptodate(struct ocfs2_caching_info *ci,
  				   struct buffer_head *bh)
  {
  	/* This should definitely *not* exist in our cache */
  	BUG_ON(ocfs2_buffer_cached(ci, bh));
  
  	set_buffer_uptodate(bh);
  
  	ocfs2_metadata_cache_io_lock(ci);
  	ocfs2_set_buffer_uptodate(ci, bh);
  	ocfs2_metadata_cache_io_unlock(ci);
  }
  
  /* 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_CACHE_INFO_MAX_ARRAY);
  	BUG_ON(index >= ci->ci_num_cached);
  	BUG_ON(!ci->ci_num_cached);
  
  	trace_ocfs2_remove_metadata_array(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		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)
  {
  	trace_ocfs2_remove_metadata_tree(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(unsigned long long)item->c_block);
  
  	rb_erase(&item->c_node, &ci->ci_cache.ci_tree);
  	ci->ci_num_cached--;
  }
  
  static void ocfs2_remove_block_from_cache(struct ocfs2_caching_info *ci,
  					  sector_t block)
  {
  	int index;
  	struct ocfs2_meta_cache_item *item = NULL;
  
  	ocfs2_metadata_cache_lock(ci);
  	trace_ocfs2_remove_block_from_cache(
  		(unsigned long long)ocfs2_metadata_cache_owner(ci),
  		(unsigned long long) block, ci->ci_num_cached,
  		ci->ci_flags);
  
  	if (ci->ci_flags & OCFS2_CACHE_FL_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);
  	}
  	ocfs2_metadata_cache_unlock(ci);
  
  	if (item)
  		kmem_cache_free(ocfs2_uptodate_cachep, item);
  }
  
  /*
   * 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 ocfs2_caching_info *ci,
  			     struct buffer_head *bh)
  {
  	sector_t block = bh->b_blocknr;
  
  	ocfs2_remove_block_from_cache(ci, block);
  }
  
  /* Called when we remove xattr clusters from an inode. */
  void ocfs2_remove_xattr_clusters_from_cache(struct ocfs2_caching_info *ci,
  					    sector_t block,
  					    u32 c_len)
  {
  	struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
  	unsigned int i, b_len = ocfs2_clusters_to_blocks(sb, 1) * c_len;
  
  	for (i = 0; i < b_len; i++, block++)
  		ocfs2_remove_block_from_cache(ci, block);
  }
  
  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);
  	if (!ocfs2_uptodate_cachep)
  		return -ENOMEM;
  
  	return 0;
  }
  
  void exit_ocfs2_uptodate_cache(void)
  {
  	if (ocfs2_uptodate_cachep)
  		kmem_cache_destroy(ocfs2_uptodate_cachep);
  }