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Date: Fri, 01 Dec 2006 02:58:14 +0300
From: Alex Tomas <alex@...sterfs.com>
To: linux-ext4@...r.kernel.org
Subject: [RFC] ext4-block-reservation patch
The patch implements free space management with
per-cpu reservation blocks for delayed allocation.
thanks, Alex
Index: linux-2.6.19-rc6/include/linux/ext4_fs.h
===================================================================
--- linux-2.6.19-rc6.orig/include/linux/ext4_fs.h 2006-11-30 02:08:35.000000000 +0300
+++ linux-2.6.19-rc6/include/linux/ext4_fs.h 2006-12-01 02:20:01.000000000 +0300
@@ -201,6 +201,7 @@ struct ext4_group_desc
#define EXT4_STATE_JDATA 0x00000001 /* journaled data exists */
#define EXT4_STATE_NEW 0x00000002 /* inode is newly created */
#define EXT4_STATE_XATTR 0x00000004 /* has in-inode xattrs */
+#define EXT4_STATE_BLOCKS_RESERVED 0x00000008 /* blocks reserved */
/* Used to pass group descriptor data when online resize is done */
struct ext4_new_group_input {
@@ -846,6 +847,12 @@ extern int ext4_should_retry_alloc(struc
extern void ext4_init_block_alloc_info(struct inode *);
extern void ext4_rsv_window_add(struct super_block *sb, struct ext4_reserve_window_node *rsv);
+/* reservation.c */
+int ext4_reserve_init(struct super_block *sb);
+void ext4_reserve_release(struct super_block *sb);
+void ext4_release_blocks(struct super_block *sb, int blocks);
+int ext4_reserve_blocks(struct super_block *sb, int blocks);
+
/* dir.c */
extern int ext4_check_dir_entry(const char *, struct inode *,
struct ext4_dir_entry_2 *,
Index: linux-2.6.19-rc6/include/linux/ext4_fs_sb.h
===================================================================
--- linux-2.6.19-rc6.orig/include/linux/ext4_fs_sb.h 2006-11-30 02:08:35.000000000 +0300
+++ linux-2.6.19-rc6/include/linux/ext4_fs_sb.h 2006-12-01 02:20:01.000000000 +0300
@@ -24,6 +24,8 @@
#endif
#include <linux/rbtree.h>
+struct ext4_reservation_slot;
+
/*
* third extended-fs super-block data in memory
*/
@@ -65,6 +67,9 @@ struct ext4_sb_info {
struct rb_root s_rsv_window_root;
struct ext4_reserve_window_node s_rsv_window_head;
+ /* global reservation structures */
+ struct ext4_reservation_slot *s_reservation_slots;
+
/* Journaling */
struct inode * s_journal_inode;
struct journal_s * s_journal;
Index: linux-2.6.19-rc6/fs/ext4/super.c
===================================================================
--- linux-2.6.19-rc6.orig/fs/ext4/super.c 2006-11-30 02:08:35.000000000 +0300
+++ linux-2.6.19-rc6/fs/ext4/super.c 2006-12-01 02:20:01.000000000 +0300
@@ -439,6 +439,7 @@ static void ext4_put_super (struct super
struct ext4_super_block *es = sbi->s_es;
int i;
+ ext4_reserve_release(sb);
ext4_ext_release(sb);
ext4_xattr_put_super(sb);
jbd2_journal_destroy(sbi->s_journal);
@@ -1866,6 +1867,7 @@ static int ext4_fill_super (struct super
ext4_lg_init(sb);
ext4_ext_init(sb);
+ ext4_reserve_init(sb);
lock_kernel();
return 0;
Index: linux-2.6.19-rc6/fs/ext4/Makefile
===================================================================
--- linux-2.6.19-rc6.orig/fs/ext4/Makefile 2006-11-30 02:08:35.000000000 +0300
+++ linux-2.6.19-rc6/fs/ext4/Makefile 2006-12-01 02:20:01.000000000 +0300
@@ -5,7 +5,8 @@
obj-$(CONFIG_EXT4DEV_FS) += ext4dev.o
ext4dev-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
- ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o lg.o
+ ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o lg.o \
+ reservation.o
ext4dev-$(CONFIG_EXT4DEV_FS_XATTR) += xattr.o xattr_user.o xattr_trusted.o
ext4dev-$(CONFIG_EXT4DEV_FS_POSIX_ACL) += acl.o
Index: linux-2.6.19-rc6/fs/ext4/reservation.c
===================================================================
--- linux-2.6.19-rc6.orig/fs/ext4/reservation.c 2006-11-30 15:32:10.563465031 +0300
+++ linux-2.6.19-rc6/fs/ext4/reservation.c 2006-12-01 02:20:01.000000000 +0300
@@ -0,0 +1,190 @@
+/*
+ * Copyright (c) 2006, Cluster File Systems, Inc, info@...sterfs.com
+ * Written by Alex Tomas <alex@...sterfs.com>
+ *
+ * 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 Licens
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-
+ */
+
+
+/*
+ * reservation.c contains routines to reserve blocks.
+ * we need this for delayed allocation, otherwise we
+ * could meet -ENOSPC at flush time
+ */
+
+/*
+ * as ->commit_write() where we're going to reserve
+ * non-allocated-yet blocks is well known hotpath,
+ * we have to make it scalable and avoid global
+ * data as much as possible
+ *
+ * there is per-sb array
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/ext4_jbd2.h>
+#include <linux/jbd.h>
+#include <linux/ext4_fs.h>
+#include <linux/quotaops.h>
+#include <linux/buffer_head.h>
+#include <linux/module.h>
+#include <linux/swap.h>
+#include <linux/proc_fs.h>
+#include <linux/pagemap.h>
+
+
+struct ext4_reservation_slot {
+ __u64 rs_reserved;
+ spinlock_t rs_lock;
+} ____cacheline_aligned;
+
+
+int ext4_reserve_local(struct super_block *sb, int blocks)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_reservation_slot *rs;
+ int rc = -ENOSPC;
+
+ preempt_disable();
+ rs = sbi->s_reservation_slots + smp_processor_id();
+
+ spin_lock(&rs->rs_lock);
+ if (likely(rs->rs_reserved >= blocks)) {
+ rs->rs_reserved -= blocks;
+ rc = 0;
+ }
+ spin_unlock(&rs->rs_lock);
+
+ preempt_enable();
+ return rc;
+}
+
+
+void ext4_rebalance_reservation(struct ext4_reservation_slot *rs, __u64 free)
+{
+ int i, used_slots = 0;
+ __u64 chunk;
+
+ /* let's know what slots have been used */
+ for (i = 0; i < NR_CPUS; i++)
+ if (rs[i].rs_reserved || i == smp_processor_id())
+ used_slots++;
+
+ /* chunk is a number of block every used
+ * slot will get. make sure it isn't 0 */
+ chunk = free + used_slots - 1;
+ do_div(chunk, used_slots);
+
+ for (i = 0; i < NR_CPUS; i++) {
+ if (free < chunk)
+ chunk = free;
+ if (rs[i].rs_reserved || i == smp_processor_id()) {
+ rs[i].rs_reserved = chunk;
+ free -= chunk;
+ BUG_ON(free < 0);
+ }
+ }
+ BUG_ON(free);
+}
+
+int ext4_reserve_global(struct super_block *sb, int blocks)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_reservation_slot *rs;
+ int i, rc = -ENOENT;
+ __u64 free = 0;
+
+ rs = sbi->s_reservation_slots;
+
+ /* lock all slots */
+ for (i = 0; i < NR_CPUS; i++) {
+ spin_lock(&rs[i].rs_lock);
+ free += rs[i].rs_reserved;
+ }
+
+ if (free >= blocks) {
+ free -= blocks;
+ ext4_rebalance_reservation(rs, free);
+ rc = 0;
+ }
+
+ for (i = 0; i < NR_CPUS; i++)
+ spin_unlock(&rs[i].rs_lock);
+
+ return rc;
+}
+
+int ext4_reserve_blocks(struct super_block *sb, int blocks)
+{
+ int ret;
+
+ BUG_ON(blocks <= 0);
+
+ ret = ext4_reserve_local(sb, blocks);
+ if (likely(ret == 0))
+ return 0;
+
+ return ext4_reserve_global(sb, blocks);
+}
+
+void ext4_release_blocks(struct super_block *sb, int blocks)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_reservation_slot *rs;
+
+ BUG_ON(blocks <= 0);
+
+ preempt_disable();
+ rs = sbi->s_reservation_slots + smp_processor_id();
+
+ spin_lock(&rs->rs_lock);
+ rs->rs_reserved += blocks;
+ spin_unlock(&rs->rs_lock);
+
+ preempt_enable();
+}
+
+int ext4_reserve_init(struct super_block *sb)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_reservation_slot *rs;
+ int i;
+
+ rs = kmalloc(sizeof(struct ext4_reservation_slot) * NR_CPUS, GFP_KERNEL);
+ if (rs == NULL)
+ return -ENOMEM;
+ sbi->s_reservation_slots = rs;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ spin_lock_init(&rs[i].rs_lock);
+ rs[i].rs_reserved = 0;
+ }
+ rs[0].rs_reserved = percpu_counter_sum(&sbi->s_freeblocks_counter);
+
+ return 0;
+}
+
+void ext4_reserve_release(struct super_block *sb)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_reservation_slot *rs;
+
+ rs = sbi->s_reservation_slots;
+ BUG_ON(sbi->s_reservation_slots == NULL);
+ kfree(sbi->s_reservation_slots);
+ sbi->s_reservation_slots = NULL;
+}
+
-
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