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ext4: Use an rbtree for tracking blocks freed during transaction.
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With this patch we track the block freed during a transaction using
red-black tree.  We also make sure contiguous blocks freed are collected
in one node in the tree.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Aneesh Kumar K.V authored and Theodore Ts'o committed Oct 16, 2008
1 parent c2774d8 commit c894058
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Showing 2 changed files with 133 additions and 77 deletions.
184 changes: 117 additions & 67 deletions fs/ext4/mballoc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2300,6 +2300,7 @@ int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
}

INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);
meta_group_info[i]->bb_free_root.rb_node = NULL;;

#ifdef DOUBLE_CHECK
{
Expand Down Expand Up @@ -2647,58 +2648,58 @@ int ext4_mb_release(struct super_block *sb)
static noinline_for_stack void
ext4_mb_free_committed_blocks(struct super_block *sb)
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
int err;
int i;
int count = 0;
int count2 = 0;
struct ext4_free_metadata *md;
struct ext4_buddy e4b;
struct ext4_group_info *db;
struct ext4_sb_info *sbi = EXT4_SB(sb);
int err, count = 0, count2 = 0;
struct ext4_free_data *entry;

if (list_empty(&sbi->s_committed_transaction))
return;

/* there is committed blocks to be freed yet */
do {
/* get next array of blocks */
md = NULL;
entry = NULL;
spin_lock(&sbi->s_md_lock);
if (!list_empty(&sbi->s_committed_transaction)) {
md = list_entry(sbi->s_committed_transaction.next,
struct ext4_free_metadata, list);
list_del(&md->list);
entry = list_entry(sbi->s_committed_transaction.next,
struct ext4_free_data, list);
list_del(&entry->list);
}
spin_unlock(&sbi->s_md_lock);

if (md == NULL)
if (entry == NULL)
break;

mb_debug("gonna free %u blocks in group %lu (0x%p):",
md->num, md->group, md);
entry->count, entry->group, entry);

err = ext4_mb_load_buddy(sb, md->group, &e4b);
err = ext4_mb_load_buddy(sb, entry->group, &e4b);
/* we expect to find existing buddy because it's pinned */
BUG_ON(err != 0);

db = e4b.bd_info;
/* there are blocks to put in buddy to make them really free */
count += md->num;
count += entry->count;
count2++;
ext4_lock_group(sb, md->group);
for (i = 0; i < md->num; i++) {
mb_debug(" %u", md->blocks[i]);
mb_free_blocks(NULL, &e4b, md->blocks[i], 1);
ext4_lock_group(sb, entry->group);
/* Take it out of per group rb tree */
rb_erase(&entry->node, &(db->bb_free_root));
mb_free_blocks(NULL, &e4b, entry->start_blk, entry->count);

if (!db->bb_free_root.rb_node) {
/* No more items in the per group rb tree
* balance refcounts from ext4_mb_free_metadata()
*/
page_cache_release(e4b.bd_buddy_page);
page_cache_release(e4b.bd_bitmap_page);
}
mb_debug("\n");
ext4_unlock_group(sb, md->group);

/* balance refcounts from ext4_mb_free_metadata() */
page_cache_release(e4b.bd_buddy_page);
page_cache_release(e4b.bd_bitmap_page);
ext4_unlock_group(sb, entry->group);

kfree(md);
kmem_cache_free(ext4_free_ext_cachep, entry);
ext4_mb_release_desc(&e4b);

} while (md);
} while (1);

mb_debug("freed %u blocks in %u structures\n", count, count2);
}
Expand Down Expand Up @@ -2771,6 +2772,16 @@ int __init init_ext4_mballoc(void)
kmem_cache_destroy(ext4_pspace_cachep);
return -ENOMEM;
}

ext4_free_ext_cachep =
kmem_cache_create("ext4_free_block_extents",
sizeof(struct ext4_free_data),
0, SLAB_RECLAIM_ACCOUNT, NULL);
if (ext4_free_ext_cachep == NULL) {
kmem_cache_destroy(ext4_pspace_cachep);
kmem_cache_destroy(ext4_ac_cachep);
return -ENOMEM;
}
return 0;
}

Expand All @@ -2779,6 +2790,7 @@ void exit_ext4_mballoc(void)
/* XXX: synchronize_rcu(); */
kmem_cache_destroy(ext4_pspace_cachep);
kmem_cache_destroy(ext4_ac_cachep);
kmem_cache_destroy(ext4_free_ext_cachep);
}


Expand Down Expand Up @@ -4415,64 +4427,102 @@ static void ext4_mb_poll_new_transaction(struct super_block *sb,
ext4_mb_free_committed_blocks(sb);
}

/*
* We can merge two free data extents only if the physical blocks
* are contiguous, AND the extents were freed by the same transaction,
* AND the blocks are associated with the same group.
*/
static int can_merge(struct ext4_free_data *entry1,
struct ext4_free_data *entry2)
{
if ((entry1->t_tid == entry2->t_tid) &&
(entry1->group == entry2->group) &&
((entry1->start_blk + entry1->count) == entry2->start_blk))
return 1;
return 0;
}

static noinline_for_stack int
ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
ext4_group_t group, ext4_grpblk_t block, int count)
{
struct ext4_group_info *db = e4b->bd_info;
struct super_block *sb = e4b->bd_sb;
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_free_metadata *md;
int i;
struct ext4_free_data *entry, *new_entry;
struct rb_node **n = &db->bb_free_root.rb_node, *node;
struct rb_node *parent = NULL, *new_node;


BUG_ON(e4b->bd_bitmap_page == NULL);
BUG_ON(e4b->bd_buddy_page == NULL);

new_entry = kmem_cache_alloc(ext4_free_ext_cachep, GFP_NOFS);
new_entry->start_blk = block;
new_entry->group = group;
new_entry->count = count;
new_entry->t_tid = handle->h_transaction->t_tid;
new_node = &new_entry->node;

ext4_lock_group(sb, group);
for (i = 0; i < count; i++) {
md = db->bb_md_cur;
if (md && db->bb_tid != handle->h_transaction->t_tid) {
db->bb_md_cur = NULL;
md = NULL;
if (!*n) {
/* first free block exent. We need to
protect buddy cache from being freed,
* otherwise we'll refresh it from
* on-disk bitmap and lose not-yet-available
* blocks */
page_cache_get(e4b->bd_buddy_page);
page_cache_get(e4b->bd_bitmap_page);
}
while (*n) {
parent = *n;
entry = rb_entry(parent, struct ext4_free_data, node);
if (block < entry->start_blk)
n = &(*n)->rb_left;
else if (block >= (entry->start_blk + entry->count))
n = &(*n)->rb_right;
else {
ext4_error(sb, __func__,
"Double free of blocks %d (%d %d)\n",
block, entry->start_blk, entry->count);
return 0;
}
}

if (md == NULL) {
ext4_unlock_group(sb, group);
md = kmalloc(sizeof(*md), GFP_NOFS);
if (md == NULL)
return -ENOMEM;
md->num = 0;
md->group = group;

ext4_lock_group(sb, group);
if (db->bb_md_cur == NULL) {
spin_lock(&sbi->s_md_lock);
list_add(&md->list, &sbi->s_active_transaction);
spin_unlock(&sbi->s_md_lock);
/* protect buddy cache from being freed,
* otherwise we'll refresh it from
* on-disk bitmap and lose not-yet-available
* blocks */
page_cache_get(e4b->bd_buddy_page);
page_cache_get(e4b->bd_bitmap_page);
db->bb_md_cur = md;
db->bb_tid = handle->h_transaction->t_tid;
mb_debug("new md 0x%p for group %lu\n",
md, md->group);
} else {
kfree(md);
md = db->bb_md_cur;
}
rb_link_node(new_node, parent, n);
rb_insert_color(new_node, &db->bb_free_root);

/* Now try to see the extent can be merged to left and right */
node = rb_prev(new_node);
if (node) {
entry = rb_entry(node, struct ext4_free_data, node);
if (can_merge(entry, new_entry)) {
new_entry->start_blk = entry->start_blk;
new_entry->count += entry->count;
rb_erase(node, &(db->bb_free_root));
spin_lock(&sbi->s_md_lock);
list_del(&entry->list);
spin_unlock(&sbi->s_md_lock);
kmem_cache_free(ext4_free_ext_cachep, entry);
}
}

BUG_ON(md->num >= EXT4_BB_MAX_BLOCKS);
md->blocks[md->num] = block + i;
md->num++;
if (md->num == EXT4_BB_MAX_BLOCKS) {
/* no more space, put full container on a sb's list */
db->bb_md_cur = NULL;
node = rb_next(new_node);
if (node) {
entry = rb_entry(node, struct ext4_free_data, node);
if (can_merge(new_entry, entry)) {
new_entry->count += entry->count;
rb_erase(node, &(db->bb_free_root));
spin_lock(&sbi->s_md_lock);
list_del(&entry->list);
spin_unlock(&sbi->s_md_lock);
kmem_cache_free(ext4_free_ext_cachep, entry);
}
}
/* Add the extent to active_transaction list */
spin_lock(&sbi->s_md_lock);
list_add(&new_entry->list, &sbi->s_active_transaction);
spin_unlock(&sbi->s_md_lock);
ext4_unlock_group(sb, group);
return 0;
}
Expand Down
26 changes: 16 additions & 10 deletions fs/ext4/mballoc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -98,23 +98,29 @@

static struct kmem_cache *ext4_pspace_cachep;
static struct kmem_cache *ext4_ac_cachep;
static struct kmem_cache *ext4_free_ext_cachep;

#ifdef EXT4_BB_MAX_BLOCKS
#undef EXT4_BB_MAX_BLOCKS
#endif
#define EXT4_BB_MAX_BLOCKS 30
struct ext4_free_data {
/* this links the free block information from group_info */
struct rb_node node;

struct ext4_free_metadata {
ext4_group_t group;
unsigned short num;
ext4_grpblk_t blocks[EXT4_BB_MAX_BLOCKS];
/* this links the free block information from ext4_sb_info */
struct list_head list;

/* group which free block extent belongs */
ext4_group_t group;

/* free block extent */
ext4_grpblk_t start_blk;
ext4_grpblk_t count;

/* transaction which freed this extent */
tid_t t_tid;
};

struct ext4_group_info {
unsigned long bb_state;
unsigned long bb_tid;
struct ext4_free_metadata *bb_md_cur;
struct rb_root bb_free_root;
unsigned short bb_first_free;
unsigned short bb_free;
unsigned short bb_fragments;
Expand Down

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