/* -*- 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 struct kmem_cache *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 %llu\n", to_purge, tree ? "array" : "tree", (unsigned long long)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 %llu, count = %u, purged = %u\n", (unsigned long long)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 %llu, query block %llu (inline = %u)\n", (unsigned long long)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. * * This can be called under lock_buffer() */ 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); } /* * Determine whether a buffer is currently out on a read-ahead request. * ip_io_sem should be held to serialize submitters with the logic here. */ int ocfs2_buffer_read_ahead(struct inode *inode, struct buffer_head *bh) { return buffer_locked(bh) && 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 %llu, num cached = %u, should be %u\n", (unsigned long long)oi->ip_blkno, ci->ci_num_cached, OCFS2_INODE_MAX_CACHE_ARRAY); mlog_bug_on_msg(!(oi->ip_flags & OCFS2_INODE_CACHE_INLINE), "Inode %llu not marked as inline anymore!\n", (unsigned long long)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 %llu to a tree cache: flags 0x%x, num = %u\n", (unsigned long long)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 %llu, block %llu, expand = %d\n", (unsigned long long)oi->ip_blkno, (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_INODE_MAX_CACHE_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! */ } } 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_mutex, 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 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 %llu, inserting block %llu\n", (unsigned long long)oi->ip_blkno, (unsigned long long)bh->b_blocknr); /* No need to recheck under spinlock - insertion is guarded by * ip_io_mutex */ 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_mutex 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); mutex_lock(&oi->ip_io_mutex); ocfs2_set_buffer_uptodate(inode, bh); mutex_unlock(&oi->ip_io_mutex); } /* 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 %llu, remove %llu, items = %u, array = %u\n", (unsigned long long)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_ocfs2_uptodate_cache(void) { if (ocfs2_uptodate_cachep) kmem_cache_destroy(ocfs2_uptodate_cachep); }