[RFC] ext4-block-reservation.patch
From: Alex Tomas
Date: Fri Dec 22 2006 - 16:11:12 EST
Index: linux-2.6.20-rc1/include/linux/ext4_fs.h
===================================================================
--- linux-2.6.20-rc1.orig/include/linux/ext4_fs.h 2006-12-14 04:14:23.000000000 +0300
+++ linux-2.6.20-rc1/include/linux/ext4_fs.h 2006-12-22 20:21:12.000000000 +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 {
@@ -808,6 +809,10 @@ extern struct ext4_group_desc * ext4_get
extern int ext4_should_retry_alloc(struct super_block *sb, int *retries);
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);
+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 *,
Index: linux-2.6.20-rc1/include/linux/ext4_fs_sb.h
===================================================================
--- linux-2.6.20-rc1.orig/include/linux/ext4_fs_sb.h 2006-12-14 04:14:23.000000000 +0300
+++ linux-2.6.20-rc1/include/linux/ext4_fs_sb.h 2006-12-22 20:20:10.000000000 +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-2.6.20-rc1/fs/ext4/super.c
===================================================================
--- linux-2.6.20-rc1.orig/fs/ext4/super.c 2006-12-14 04:14:23.000000000 +0300
+++ linux-2.6.20-rc1/fs/ext4/super.c 2006-12-22 20:20:10.000000000 +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);
@@ -1867,6 +1868,7 @@ static int ext4_fill_super (struct super
"writeback");
ext4_ext_init(sb);
+ ext4_reserve_init(sb);
lock_kernel();
return 0;
Index: linux-2.6.20-rc1/fs/ext4/balloc.c
===================================================================
--- linux-2.6.20-rc1.orig/fs/ext4/balloc.c 2006-12-14 04:14:23.000000000 +0300
+++ linux-2.6.20-rc1/fs/ext4/balloc.c 2006-12-22 20:32:11.000000000 +0300
@@ -630,8 +630,10 @@ void ext4_free_blocks(handle_t *handle,
return;
}
ext4_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
- if (dquot_freed_blocks)
+ if (dquot_freed_blocks) {
+ ext4_release_blocks(sb, dquot_freed_blocks);
DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
+ }
return;
}
@@ -1440,7 +1442,7 @@ ext4_fsblk_t ext4_new_blocks(handle_t *h
struct ext4_sb_info *sbi;
struct ext4_reserve_window_node *my_rsv = NULL;
struct ext4_block_alloc_info *block_i;
- unsigned short windowsz = 0;
+ unsigned short windowsz = 0, reserved = 0;
#ifdef EXT4FS_DEBUG
static int goal_hits, goal_attempts;
#endif
@@ -1462,6 +1464,13 @@ ext4_fsblk_t ext4_new_blocks(handle_t *h
return 0;
}
+ if (!(EXT4_I(inode)->i_state & EXT4_STATE_BLOCKS_RESERVED)) {
+ *errp = ext4_reserve_blocks(sb, num);
+ if (*errp)
+ return 0;
+ reserved = num;
+ }
+
sbi = EXT4_SB(sb);
es = EXT4_SB(sb)->s_es;
ext4_debug("goal=%lu.\n", goal);
@@ -1674,8 +1683,11 @@ out:
/*
* Undo the block allocation
*/
- if (!performed_allocation)
+ if (!performed_allocation) {
DQUOT_FREE_BLOCK(inode, *count);
+ if (reserved)
+ ext4_release_blocks(sb, reserved);
+ }
brelse(bitmap_bh);
return 0;
}
@@ -1834,3 +1846,161 @@ unsigned long ext4_bg_num_gdb(struct sup
return ext4_bg_num_gdb_meta(sb,group);
}
+
+/*
+ * 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
+ */
+
+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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