uptodate.c | Explore in Territory

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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.
 *
 * 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 { … };

static struct kmem_cache *ocfs2_uptodate_cachep;

u64 ocfs2_metadata_cache_owner(struct ocfs2_caching_info *ci)
{ … }

struct super_block *ocfs2_metadata_cache_get_super(struct ocfs2_caching_info *ci)
{ … }

static void ocfs2_metadata_cache_lock(struct ocfs2_caching_info *ci)
{ … }

static void ocfs2_metadata_cache_unlock(struct ocfs2_caching_info *ci)
{ … }

void ocfs2_metadata_cache_io_lock(struct ocfs2_caching_info *ci)
{ … }

void ocfs2_metadata_cache_io_unlock(struct ocfs2_caching_info *ci)
{ … }


static void ocfs2_metadata_cache_reset(struct ocfs2_caching_info *ci,
				       int clear)
{ … }

void ocfs2_metadata_cache_init(struct ocfs2_caching_info *ci,
			       const struct ocfs2_caching_operations *ops)
{ … }

void ocfs2_metadata_cache_exit(struct ocfs2_caching_info *ci)
{ … }


/* 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)
{ … }

/* 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)
{ … }

/* 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)
{ … }

/* 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)
{ … }

static int ocfs2_buffer_cached(struct ocfs2_caching_info *ci,
			       struct buffer_head *bh)
{ … }

/* 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)
{ … }

/*
 * 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)
{ … }

/* Requires ip_lock */
static void ocfs2_append_cache_array(struct ocfs2_caching_info *ci,
				     sector_t block)
{ … }

/* 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)
{ … }

/* co_cache_lock() must be held */
static inline int ocfs2_insert_can_use_array(struct ocfs2_caching_info *ci)
{ … }

/* 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)
{ … }

/* 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)
{ … }

/* 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)
{ … }

/* 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)
{ … }

/* Requires ip_lock. */
static void ocfs2_remove_metadata_array(struct ocfs2_caching_info *ci,
					int index)
{ … }

/* Requires ip_lock. */
static void ocfs2_remove_metadata_tree(struct ocfs2_caching_info *ci,
				       struct ocfs2_meta_cache_item *item)
{ … }

static void ocfs2_remove_block_from_cache(struct ocfs2_caching_info *ci,
					  sector_t block)
{ … }

/*
 * 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)
{ … }

/* 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)
{ … }

int __init init_ocfs2_uptodate_cache(void)
{ … }

void exit_ocfs2_uptodate_cache(void)
{ … }
linux/fs/ocfs2/uptodate.c
