[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>
diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
new file mode 100644
index 0000000..f2fb40c
--- /dev/null
+++ b/fs/ocfs2/extent_map.c
@@ -0,0 +1,994 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * extent_map.c
+ *
+ * In-memory extent map for OCFS2. Man, this code was prettier in
+ * the library.
+ *
+ * Copyright (C) 2004 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, version 2, as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/rbtree.h>
+
+#define MLOG_MASK_PREFIX ML_EXTENT_MAP
+#include <cluster/masklog.h>
+
+#include "ocfs2.h"
+
+#include "extent_map.h"
+#include "inode.h"
+#include "super.h"
+
+#include "buffer_head_io.h"
+
+
+/*
+ * SUCK SUCK SUCK
+ * Our headers are so bad that struct ocfs2_extent_map is in ocfs.h
+ */
+
+struct ocfs2_extent_map_entry {
+ struct rb_node e_node;
+ int e_tree_depth;
+ struct ocfs2_extent_rec e_rec;
+};
+
+struct ocfs2_em_insert_context {
+ int need_left;
+ int need_right;
+ struct ocfs2_extent_map_entry *new_ent;
+ struct ocfs2_extent_map_entry *old_ent;
+ struct ocfs2_extent_map_entry *left_ent;
+ struct ocfs2_extent_map_entry *right_ent;
+};
+
+static kmem_cache_t *ocfs2_em_ent_cachep = NULL;
+
+
+static struct ocfs2_extent_map_entry *
+ocfs2_extent_map_lookup(struct ocfs2_extent_map *em,
+ u32 cpos, u32 clusters,
+ struct rb_node ***ret_p,
+ struct rb_node **ret_parent);
+static int ocfs2_extent_map_insert(struct inode *inode,
+ struct ocfs2_extent_rec *rec,
+ int tree_depth);
+static int ocfs2_extent_map_insert_entry(struct ocfs2_extent_map *em,
+ struct ocfs2_extent_map_entry *ent);
+static int ocfs2_extent_map_find_leaf(struct inode *inode,
+ u32 cpos, u32 clusters,
+ struct ocfs2_extent_list *el);
+static int ocfs2_extent_map_lookup_read(struct inode *inode,
+ u32 cpos, u32 clusters,
+ struct ocfs2_extent_map_entry **ret_ent);
+static int ocfs2_extent_map_try_insert(struct inode *inode,
+ struct ocfs2_extent_rec *rec,
+ int tree_depth,
+ struct ocfs2_em_insert_context *ctxt);
+
+/* returns 1 only if the rec contains all the given clusters -- that is that
+ * rec's cpos is <= the cluster cpos and that the rec endpoint (cpos +
+ * clusters) is >= the argument's endpoint */
+static int ocfs2_extent_rec_contains_clusters(struct ocfs2_extent_rec *rec,
+ u32 cpos, u32 clusters)
+{
+ if (le32_to_cpu(rec->e_cpos) > cpos)
+ return 0;
+ if (cpos + clusters > le32_to_cpu(rec->e_cpos) +
+ le32_to_cpu(rec->e_clusters))
+ return 0;
+ return 1;
+}
+
+
+/*
+ * Find an entry in the tree that intersects the region passed in.
+ * Note that this will find straddled intervals, it is up to the
+ * callers to enforce any boundary conditions.
+ *
+ * Callers must hold ip_lock. This lookup is not guaranteed to return
+ * a tree_depth 0 match, and as such can race inserts if the lock
+ * were not held.
+ *
+ * The rb_node garbage lets insertion share the search. Trivial
+ * callers pass NULL.
+ */
+static struct ocfs2_extent_map_entry *
+ocfs2_extent_map_lookup(struct ocfs2_extent_map *em,
+ u32 cpos, u32 clusters,
+ struct rb_node ***ret_p,
+ struct rb_node **ret_parent)
+{
+ struct rb_node **p = &em->em_extents.rb_node;
+ struct rb_node *parent = NULL;
+ struct ocfs2_extent_map_entry *ent = NULL;
+
+ while (*p)
+ {
+ parent = *p;
+ ent = rb_entry(parent, struct ocfs2_extent_map_entry,
+ e_node);
+ if ((cpos + clusters) <= le32_to_cpu(ent->e_rec.e_cpos)) {
+ p = &(*p)->rb_left;
+ ent = NULL;
+ } else if (cpos >= (le32_to_cpu(ent->e_rec.e_cpos) +
+ le32_to_cpu(ent->e_rec.e_clusters))) {
+ p = &(*p)->rb_right;
+ ent = NULL;
+ } else
+ break;
+ }
+
+ if (ret_p != NULL)
+ *ret_p = p;
+ if (ret_parent != NULL)
+ *ret_parent = parent;
+ return ent;
+}
+
+/*
+ * Find the leaf containing the interval we want. While we're on our
+ * way down the tree, fill in every record we see at any depth, because
+ * we might want it later.
+ *
+ * Note that this code is run without ip_lock. That's because it
+ * sleeps while reading. If someone is also filling the extent list at
+ * the same time we are, we might have to restart.
+ */
+static int ocfs2_extent_map_find_leaf(struct inode *inode,
+ u32 cpos, u32 clusters,
+ struct ocfs2_extent_list *el)
+{
+ int i, ret;
+ struct buffer_head *eb_bh = NULL;
+ u64 blkno;
+ u32 rec_end;
+ struct ocfs2_extent_block *eb;
+ struct ocfs2_extent_rec *rec;
+
+ /*
+ * The bh data containing the el cannot change here, because
+ * we hold alloc_sem. So we can do this without other
+ * locks.
+ */
+ while (el->l_tree_depth)
+ {
+ blkno = 0;
+ for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
+ rec = &el->l_recs[i];
+ rec_end = (le32_to_cpu(rec->e_cpos) +
+ le32_to_cpu(rec->e_clusters));
+
+ ret = -EBADR;
+ if (rec_end > OCFS2_I(inode)->ip_clusters) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+
+ if (rec_end <= cpos) {
+ ret = ocfs2_extent_map_insert(inode, rec,
+ le16_to_cpu(el->l_tree_depth));
+ if (ret && (ret != -EEXIST)) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+ continue;
+ }
+ if ((cpos + clusters) <= le32_to_cpu(rec->e_cpos)) {
+ ret = ocfs2_extent_map_insert(inode, rec,
+ le16_to_cpu(el->l_tree_depth));
+ if (ret && (ret != -EEXIST)) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+ continue;
+ }
+
+ /*
+ * We've found a record that matches our
+ * interval. We don't insert it because we're
+ * about to traverse it.
+ */
+
+ /* Check to see if we're stradling */
+ ret = -ESRCH;
+ if (!ocfs2_extent_rec_contains_clusters(rec,
+ cpos,
+ clusters)) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+
+ /*
+ * If we've already found a record, the el has
+ * two records covering the same interval.
+ * EEEK!
+ */
+ ret = -EBADR;
+ if (blkno) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+
+ blkno = le64_to_cpu(rec->e_blkno);
+ }
+
+ /*
+ * We don't support holes, and we're still up
+ * in the branches, so we'd better have found someone
+ */
+ ret = -EBADR;
+ if (!blkno) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+
+ if (eb_bh) {
+ brelse(eb_bh);
+ eb_bh = NULL;
+ }
+ ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
+ blkno, &eb_bh, OCFS2_BH_CACHED,
+ inode);
+ if (ret) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+ eb = (struct ocfs2_extent_block *)eb_bh->b_data;
+ if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
+ OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
+ ret = -EIO;
+ goto out_free;
+ }
+ el = &eb->h_list;
+ }
+
+ if (el->l_tree_depth)
+ BUG();
+
+ for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
+ rec = &el->l_recs[i];
+ ret = ocfs2_extent_map_insert(inode, rec,
+ le16_to_cpu(el->l_tree_depth));
+ if (ret) {
+ mlog_errno(ret);
+ goto out_free;
+ }
+ }
+
+ ret = 0;
+
+out_free:
+ if (eb_bh)
+ brelse(eb_bh);
+
+ return ret;
+}
+
+/*
+ * This lookup actually will read from disk. It has one invariant:
+ * It will never re-traverse blocks. This means that all inserts should
+ * be new regions or more granular regions (both allowed by insert).
+ */
+static int ocfs2_extent_map_lookup_read(struct inode *inode,
+ u32 cpos,
+ u32 clusters,
+ struct ocfs2_extent_map_entry **ret_ent)
+{
+ int ret;
+ u64 blkno;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *ent;
+ struct buffer_head *bh = NULL;
+ struct ocfs2_extent_block *eb;
+ struct ocfs2_dinode *di;
+ struct ocfs2_extent_list *el;
+
+ spin_lock(&OCFS2_I(inode)->ip_lock);
+ ent = ocfs2_extent_map_lookup(em, cpos, clusters, NULL, NULL);
+ if (ent) {
+ if (!ent->e_tree_depth) {
+ spin_unlock(&OCFS2_I(inode)->ip_lock);
+ *ret_ent = ent;
+ return 0;
+ }
+ blkno = le64_to_cpu(ent->e_rec.e_blkno);
+ spin_unlock(&OCFS2_I(inode)->ip_lock);
+
+ ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), blkno, &bh,
+ OCFS2_BH_CACHED, inode);
+ if (ret) {
+ mlog_errno(ret);
+ if (bh)
+ brelse(bh);
+ return ret;
+ }
+ eb = (struct ocfs2_extent_block *)bh->b_data;
+ if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
+ OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
+ brelse(bh);
+ return -EIO;
+ }
+ el = &eb->h_list;
+ } else {
+ spin_unlock(&OCFS2_I(inode)->ip_lock);
+
+ ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
+ OCFS2_I(inode)->ip_blkno, &bh,
+ OCFS2_BH_CACHED, inode);
+ if (ret) {
+ mlog_errno(ret);
+ if (bh)
+ brelse(bh);
+ return ret;
+ }
+ di = (struct ocfs2_dinode *)bh->b_data;
+ if (!OCFS2_IS_VALID_DINODE(di)) {
+ brelse(bh);
+ OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, di);
+ return -EIO;
+ }
+ el = &di->id2.i_list;
+ }
+
+ ret = ocfs2_extent_map_find_leaf(inode, cpos, clusters, el);
+ brelse(bh);
+ if (ret) {
+ mlog_errno(ret);
+ return ret;
+ }
+
+ ent = ocfs2_extent_map_lookup(em, cpos, clusters, NULL, NULL);
+ if (!ent) {
+ ret = -ESRCH;
+ mlog_errno(ret);
+ return ret;
+ }
+
+ if (ent->e_tree_depth)
+ BUG(); /* FIXME: Make sure this isn't a corruption */
+
+ *ret_ent = ent;
+
+ return 0;
+}
+
+/*
+ * Callers must hold ip_lock. This can insert pieces of the tree,
+ * thus racing lookup if the lock weren't held.
+ */
+static int ocfs2_extent_map_insert_entry(struct ocfs2_extent_map *em,
+ struct ocfs2_extent_map_entry *ent)
+{
+ struct rb_node **p, *parent;
+ struct ocfs2_extent_map_entry *old_ent;
+
+ old_ent = ocfs2_extent_map_lookup(em, le32_to_cpu(ent->e_rec.e_cpos),
+ le32_to_cpu(ent->e_rec.e_clusters),
+ &p, &parent);
+ if (old_ent)
+ return -EEXIST;
+
+ rb_link_node(&ent->e_node, parent, p);
+ rb_insert_color(&ent->e_node, &em->em_extents);
+
+ return 0;
+}
+
+
+/*
+ * Simple rule: on any return code other than -EAGAIN, anything left
+ * in the insert_context will be freed.
+ */
+static int ocfs2_extent_map_try_insert(struct inode *inode,
+ struct ocfs2_extent_rec *rec,
+ int tree_depth,
+ struct ocfs2_em_insert_context *ctxt)
+{
+ int ret;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *old_ent;
+
+ ctxt->need_left = 0;
+ ctxt->need_right = 0;
+ ctxt->old_ent = NULL;
+
+ spin_lock(&OCFS2_I(inode)->ip_lock);
+ ret = ocfs2_extent_map_insert_entry(em, ctxt->new_ent);
+ if (!ret) {
+ ctxt->new_ent = NULL;
+ goto out_unlock;
+ }
+
+ old_ent = ocfs2_extent_map_lookup(em, le32_to_cpu(rec->e_cpos),
+ le32_to_cpu(rec->e_clusters), NULL,
+ NULL);
+
+ if (!old_ent)
+ BUG();
+
+ ret = -EEXIST;
+ if (old_ent->e_tree_depth < tree_depth)
+ goto out_unlock;
+
+ if (old_ent->e_tree_depth == tree_depth) {
+ if (!memcmp(rec, &old_ent->e_rec,
+ sizeof(struct ocfs2_extent_rec)))
+ ret = 0;
+
+ /* FIXME: Should this be ESRCH/EBADR??? */
+ goto out_unlock;
+ }
+
+ /*
+ * We do it in this order specifically so that no actual tree
+ * changes occur until we have all the pieces we need. We
+ * don't want malloc failures to leave an inconsistent tree.
+ * Whenever we drop the lock, another process could be
+ * inserting. Also note that, if another process just beat us
+ * to an insert, we might not need the same pieces we needed
+ * the first go round. In the end, the pieces we need will
+ * be used, and the pieces we don't will be freed.
+ */
+ ctxt->need_left = !!(le32_to_cpu(rec->e_cpos) >
+ le32_to_cpu(old_ent->e_rec.e_cpos));
+ ctxt->need_right = !!((le32_to_cpu(old_ent->e_rec.e_cpos) +
+ le32_to_cpu(old_ent->e_rec.e_clusters)) >
+ (le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)));
+ ret = -EAGAIN;
+ if (ctxt->need_left) {
+ if (!ctxt->left_ent)
+ goto out_unlock;
+ *(ctxt->left_ent) = *old_ent;
+ ctxt->left_ent->e_rec.e_clusters =
+ cpu_to_le32(le32_to_cpu(rec->e_cpos) -
+ le32_to_cpu(ctxt->left_ent->e_rec.e_cpos));
+ }
+ if (ctxt->need_right) {
+ if (!ctxt->right_ent)
+ goto out_unlock;
+ *(ctxt->right_ent) = *old_ent;
+ ctxt->right_ent->e_rec.e_cpos =
+ cpu_to_le32(le32_to_cpu(rec->e_cpos) +
+ le32_to_cpu(rec->e_clusters));
+ ctxt->right_ent->e_rec.e_clusters =
+ cpu_to_le32((le32_to_cpu(old_ent->e_rec.e_cpos) +
+ le32_to_cpu(old_ent->e_rec.e_clusters)) -
+ le32_to_cpu(ctxt->right_ent->e_rec.e_cpos));
+ }
+
+ rb_erase(&old_ent->e_node, &em->em_extents);
+ /* Now that he's erased, set him up for deletion */
+ ctxt->old_ent = old_ent;
+
+ if (ctxt->need_left) {
+ ret = ocfs2_extent_map_insert_entry(em,
+ ctxt->left_ent);
+ if (ret)
+ goto out_unlock;
+ ctxt->left_ent = NULL;
+ }
+
+ if (ctxt->need_right) {
+ ret = ocfs2_extent_map_insert_entry(em,
+ ctxt->right_ent);
+ if (ret)
+ goto out_unlock;
+ ctxt->right_ent = NULL;
+ }
+
+ ret = ocfs2_extent_map_insert_entry(em, ctxt->new_ent);
+
+ if (!ret)
+ ctxt->new_ent = NULL;
+
+out_unlock:
+ spin_unlock(&OCFS2_I(inode)->ip_lock);
+
+ return ret;
+}
+
+
+static int ocfs2_extent_map_insert(struct inode *inode,
+ struct ocfs2_extent_rec *rec,
+ int tree_depth)
+{
+ int ret;
+ struct ocfs2_em_insert_context ctxt = {0, };
+
+ if ((le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)) >
+ OCFS2_I(inode)->ip_map.em_clusters) {
+ ret = -EBADR;
+ mlog_errno(ret);
+ return ret;
+ }
+
+ /* Zero e_clusters means a truncated tail record. It better be EOF */
+ if (!rec->e_clusters) {
+ if ((le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)) !=
+ OCFS2_I(inode)->ip_map.em_clusters) {
+ ret = -EBADR;
+ mlog_errno(ret);
+ return ret;
+ }
+
+ /* Ignore the truncated tail */
+ return 0;
+ }
+
+ ret = -ENOMEM;
+ ctxt.new_ent = kmem_cache_alloc(ocfs2_em_ent_cachep,
+ GFP_KERNEL);
+ if (!ctxt.new_ent) {
+ mlog_errno(ret);
+ return ret;
+ }
+
+ ctxt.new_ent->e_rec = *rec;
+ ctxt.new_ent->e_tree_depth = tree_depth;
+
+ do {
+ ret = -ENOMEM;
+ if (ctxt.need_left && !ctxt.left_ent) {
+ ctxt.left_ent =
+ kmem_cache_alloc(ocfs2_em_ent_cachep,
+ GFP_KERNEL);
+ if (!ctxt.left_ent)
+ break;
+ }
+ if (ctxt.need_right && !ctxt.right_ent) {
+ ctxt.right_ent =
+ kmem_cache_alloc(ocfs2_em_ent_cachep,
+ GFP_KERNEL);
+ if (!ctxt.right_ent)
+ break;
+ }
+
+ ret = ocfs2_extent_map_try_insert(inode, rec,
+ tree_depth, &ctxt);
+ } while (ret == -EAGAIN);
+
+ if (ret < 0)
+ mlog_errno(ret);
+
+ if (ctxt.left_ent)
+ kmem_cache_free(ocfs2_em_ent_cachep, ctxt.left_ent);
+ if (ctxt.right_ent)
+ kmem_cache_free(ocfs2_em_ent_cachep, ctxt.right_ent);
+ if (ctxt.old_ent)
+ kmem_cache_free(ocfs2_em_ent_cachep, ctxt.old_ent);
+ if (ctxt.new_ent)
+ kmem_cache_free(ocfs2_em_ent_cachep, ctxt.new_ent);
+
+ return ret;
+}
+
+/*
+ * Append this record to the tail of the extent map. It must be
+ * tree_depth 0. The record might be an extension of an existing
+ * record, and as such that needs to be handled. eg:
+ *
+ * Existing record in the extent map:
+ *
+ * cpos = 10, len = 10
+ * |---------|
+ *
+ * New Record:
+ *
+ * cpos = 10, len = 20
+ * |------------------|
+ *
+ * The passed record is the new on-disk record. The new_clusters value
+ * is how many clusters were added to the file. If the append is a
+ * contiguous append, the new_clusters has been added to
+ * rec->e_clusters. If the append is an entirely new extent, then
+ * rec->e_clusters is == new_clusters.
+ */
+int ocfs2_extent_map_append(struct inode *inode,
+ struct ocfs2_extent_rec *rec,
+ u32 new_clusters)
+{
+ int ret;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *ent;
+ struct ocfs2_extent_rec *old;
+
+ BUG_ON(!new_clusters);
+ BUG_ON(le32_to_cpu(rec->e_clusters) < new_clusters);
+
+ if (em->em_clusters < OCFS2_I(inode)->ip_clusters) {
+ /*
+ * Size changed underneath us on disk. Drop any
+ * straddling records and update our idea of
+ * i_clusters
+ */
+ ocfs2_extent_map_drop(inode, em->em_clusters - 1);
+ em->em_clusters = OCFS2_I(inode)->ip_clusters;
+ }
+
+ mlog_bug_on_msg((le32_to_cpu(rec->e_cpos) +
+ le32_to_cpu(rec->e_clusters)) !=
+ (em->em_clusters + new_clusters),
+ "Inode %"MLFu64":\n"
+ "rec->e_cpos = %u + rec->e_clusters = %u = %u\n"
+ "em->em_clusters = %u + new_clusters = %u = %u\n",
+ OCFS2_I(inode)->ip_blkno,
+ le32_to_cpu(rec->e_cpos), le32_to_cpu(rec->e_clusters),
+ le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters),
+ em->em_clusters, new_clusters,
+ em->em_clusters + new_clusters);
+
+ em->em_clusters += new_clusters;
+
+ ret = -ENOENT;
+ if (le32_to_cpu(rec->e_clusters) > new_clusters) {
+ /* This is a contiguous append */
+ ent = ocfs2_extent_map_lookup(em, le32_to_cpu(rec->e_cpos), 1,
+ NULL, NULL);
+ if (ent) {
+ old = &ent->e_rec;
+ BUG_ON((le32_to_cpu(rec->e_cpos) +
+ le32_to_cpu(rec->e_clusters)) !=
+ (le32_to_cpu(old->e_cpos) +
+ le32_to_cpu(old->e_clusters) +
+ new_clusters));
+ if (ent->e_tree_depth == 0) {
+ BUG_ON(le32_to_cpu(old->e_cpos) !=
+ le32_to_cpu(rec->e_cpos));
+ BUG_ON(le64_to_cpu(old->e_blkno) !=
+ le64_to_cpu(rec->e_blkno));
+ ret = 0;
+ }
+ /*
+ * Let non-leafs fall through as -ENOENT to
+ * force insertion of the new leaf.
+ */
+ le32_add_cpu(&old->e_clusters, new_clusters);
+ }
+ }
+
+ if (ret == -ENOENT)
+ ret = ocfs2_extent_map_insert(inode, rec, 0);
+ if (ret < 0)
+ mlog_errno(ret);
+ return ret;
+}
+
+#if 0
+/* Code here is included but defined out as it completes the extent
+ * map api and may be used in the future. */
+
+/*
+ * Look up the record containing this cluster offset. This record is
+ * part of the extent map. Do not free it. Any changes you make to
+ * it will reflect in the extent map. So, if your last extent
+ * is (cpos = 10, clusters = 10) and you truncate the file by 5
+ * clusters, you can do:
+ *
+ * ret = ocfs2_extent_map_get_rec(em, orig_size - 5, &rec);
+ * rec->e_clusters -= 5;
+ *
+ * The lookup does not read from disk. If the map isn't filled in for
+ * an entry, you won't find it.
+ *
+ * Also note that the returned record is valid until alloc_sem is
+ * dropped. After that, truncate and extend can happen. Caveat Emptor.
+ */
+int ocfs2_extent_map_get_rec(struct inode *inode, u32 cpos,
+ struct ocfs2_extent_rec **rec,
+ int *tree_depth)
+{
+ int ret = -ENOENT;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *ent;
+
+ *rec = NULL;
+
+ if (cpos >= OCFS2_I(inode)->ip_clusters)
+ return -EINVAL;
+
+ if (cpos >= em->em_clusters) {
+ /*
+ * Size changed underneath us on disk. Drop any
+ * straddling records and update our idea of
+ * i_clusters
+ */
+ ocfs2_extent_map_drop(inode, em->em_clusters - 1);
+ em->em_clusters = OCFS2_I(inode)->ip_clusters ;
+ }
+
+ ent = ocfs2_extent_map_lookup(&OCFS2_I(inode)->ip_map, cpos, 1,
+ NULL, NULL);
+
+ if (ent) {
+ *rec = &ent->e_rec;
+ if (tree_depth)
+ *tree_depth = ent->e_tree_depth;
+ ret = 0;
+ }
+
+ return ret;
+}
+
+int ocfs2_extent_map_get_clusters(struct inode *inode,
+ u32 v_cpos, int count,
+ u32 *p_cpos, int *ret_count)
+{
+ int ret;
+ u32 coff, ccount;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *ent = NULL;
+
+ *p_cpos = ccount = 0;
+
+ if ((v_cpos + count) > OCFS2_I(inode)->ip_clusters)
+ return -EINVAL;
+
+ if ((v_cpos + count) > em->em_clusters) {
+ /*
+ * Size changed underneath us on disk. Drop any
+ * straddling records and update our idea of
+ * i_clusters
+ */
+ ocfs2_extent_map_drop(inode, em->em_clusters - 1);
+ em->em_clusters = OCFS2_I(inode)->ip_clusters;
+ }
+
+
+ ret = ocfs2_extent_map_lookup_read(inode, v_cpos, count, &ent);
+ if (ret)
+ return ret;
+
+ if (ent) {
+ /* We should never find ourselves straddling an interval */
+ if (!ocfs2_extent_rec_contains_clusters(&ent->e_rec,
+ v_cpos,
+ count))
+ return -ESRCH;
+
+ coff = v_cpos - le32_to_cpu(ent->e_rec.e_cpos);
+ *p_cpos = ocfs2_blocks_to_clusters(inode->i_sb,
+ le64_to_cpu(ent->e_rec.e_blkno)) +
+ coff;
+
+ if (ret_count)
+ *ret_count = le32_to_cpu(ent->e_rec.e_clusters) - coff;
+
+ return 0;
+ }
+
+
+ return -ENOENT;
+}
+
+#endif /* 0 */
+
+int ocfs2_extent_map_get_blocks(struct inode *inode,
+ u64 v_blkno, int count,
+ u64 *p_blkno, int *ret_count)
+{
+ int ret;
+ u64 boff;
+ u32 cpos, clusters;
+ int bpc = ocfs2_clusters_to_blocks(inode->i_sb, 1);
+ struct ocfs2_extent_map_entry *ent = NULL;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_rec *rec;
+
+ *p_blkno = 0;
+
+ cpos = ocfs2_blocks_to_clusters(inode->i_sb, v_blkno);
+ clusters = ocfs2_blocks_to_clusters(inode->i_sb,
+ (u64)count + bpc - 1);
+ if ((cpos + clusters) > OCFS2_I(inode)->ip_clusters) {
+ ret = -EINVAL;
+ mlog_errno(ret);
+ return ret;
+ }
+
+ if ((cpos + clusters) > em->em_clusters) {
+ /*
+ * Size changed underneath us on disk. Drop any
+ * straddling records and update our idea of
+ * i_clusters
+ */
+ ocfs2_extent_map_drop(inode, em->em_clusters - 1);
+ em->em_clusters = OCFS2_I(inode)->ip_clusters;
+ }
+
+ ret = ocfs2_extent_map_lookup_read(inode, cpos, clusters, &ent);
+ if (ret) {
+ mlog_errno(ret);
+ return ret;
+ }
+
+ if (ent)
+ {
+ rec = &ent->e_rec;
+
+ /* We should never find ourselves straddling an interval */
+ if (!ocfs2_extent_rec_contains_clusters(rec, cpos, clusters)) {
+ ret = -ESRCH;
+ mlog_errno(ret);
+ return ret;
+ }
+
+ boff = ocfs2_clusters_to_blocks(inode->i_sb, cpos -
+ le32_to_cpu(rec->e_cpos));
+ boff += (v_blkno & (u64)(bpc - 1));
+ *p_blkno = le64_to_cpu(rec->e_blkno) + boff;
+
+ if (ret_count) {
+ *ret_count = ocfs2_clusters_to_blocks(inode->i_sb,
+ le32_to_cpu(rec->e_clusters)) - boff;
+ }
+
+ return 0;
+ }
+
+ return -ENOENT;
+}
+
+int ocfs2_extent_map_init(struct inode *inode)
+{
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+
+ em->em_extents = RB_ROOT;
+ em->em_clusters = 0;
+
+ return 0;
+}
+
+/* Needs the lock */
+static void __ocfs2_extent_map_drop(struct inode *inode,
+ u32 new_clusters,
+ struct rb_node **free_head,
+ struct ocfs2_extent_map_entry **tail_ent)
+{
+ struct rb_node *node, *next;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *ent;
+
+ *free_head = NULL;
+
+ ent = NULL;
+ node = rb_last(&em->em_extents);
+ while (node)
+ {
+ next = rb_prev(node);
+
+ ent = rb_entry(node, struct ocfs2_extent_map_entry,
+ e_node);
+ if (le32_to_cpu(ent->e_rec.e_cpos) < new_clusters)
+ break;
+
+ rb_erase(&ent->e_node, &em->em_extents);
+
+ node->rb_right = *free_head;
+ *free_head = node;
+
+ ent = NULL;
+ node = next;
+ }
+
+ /* Do we have an entry straddling new_clusters? */
+ if (tail_ent) {
+ if (ent &&
+ ((le32_to_cpu(ent->e_rec.e_cpos) +
+ le32_to_cpu(ent->e_rec.e_clusters)) > new_clusters))
+ *tail_ent = ent;
+ else
+ *tail_ent = NULL;
+ }
+}
+
+static void __ocfs2_extent_map_drop_cleanup(struct rb_node *free_head)
+{
+ struct rb_node *node;
+ struct ocfs2_extent_map_entry *ent;
+
+ while (free_head) {
+ node = free_head;
+ free_head = node->rb_right;
+
+ ent = rb_entry(node, struct ocfs2_extent_map_entry,
+ e_node);
+ kmem_cache_free(ocfs2_em_ent_cachep, ent);
+ }
+}
+
+/*
+ * Remove all entries past new_clusters, inclusive of an entry that
+ * contains new_clusters. This is effectively a cache forget.
+ *
+ * If you want to also clip the last extent by some number of clusters,
+ * you need to call ocfs2_extent_map_trunc().
+ * This code does not check or modify ip_clusters.
+ */
+int ocfs2_extent_map_drop(struct inode *inode, u32 new_clusters)
+{
+ struct rb_node *free_head = NULL;
+ struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+ struct ocfs2_extent_map_entry *ent;
+
+ spin_lock(&OCFS2_I(inode)->ip_lock);
+
+ __ocfs2_extent_map_drop(inode, new_clusters, &free_head, &ent);
+
+ if (ent) {
+ rb_erase(&ent->e_node, &em->em_extents);
+ ent->e_node.rb_right = free_head;
+ free_head = &ent->e_node;
+ }
+
+ spin_unlock(&OCFS2_I(inode)->ip_lock);
+
+ if (free_head)
+ __ocfs2_extent_map_drop_cleanup(free_head);
+
+ return 0;
+}
+
+/*
+ * Remove all entries past new_clusters and also clip any extent
+ * straddling new_clusters, if there is one. This does not check
+ * or modify ip_clusters
+ */
+int ocfs2_extent_map_trunc(struct inode *inode, u32 new_clusters)
+{
+ struct rb_node *free_head = NULL;
+ struct ocfs2_extent_map_entry *ent = NULL;
+
+ spin_lock(&OCFS2_I(inode)->ip_lock);
+
+ __ocfs2_extent_map_drop(inode, new_clusters, &free_head, &ent);
+
+ if (ent)
+ ent->e_rec.e_clusters = cpu_to_le32(new_clusters -
+ le32_to_cpu(ent->e_rec.e_cpos));
+
+ OCFS2_I(inode)->ip_map.em_clusters = new_clusters;
+
+ spin_unlock(&OCFS2_I(inode)->ip_lock);
+
+ if (free_head)
+ __ocfs2_extent_map_drop_cleanup(free_head);
+
+ return 0;
+}
+
+int __init init_ocfs2_extent_maps(void)
+{
+ ocfs2_em_ent_cachep =
+ kmem_cache_create("ocfs2_em_ent",
+ sizeof(struct ocfs2_extent_map_entry),
+ 0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+ if (!ocfs2_em_ent_cachep)
+ return -ENOMEM;
+
+ return 0;
+}
+
+void __exit exit_ocfs2_extent_maps(void)
+{
+ kmem_cache_destroy(ocfs2_em_ent_cachep);
+}