/* -*- 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 %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. */
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 %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) */
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);
}
