[PATCH v3] fs/ext4: increase parallelism in updating ext4 orphan list

[T Makphaibulchoke <tmac@hp.com>]

This patch allows more concurrency of updates of ext4 orphan list,
while still maintaining the integrity of both the in memory and on
disk orphan lists of each update.

This is accomplished by using a mutex from an array of mutexes, indexed
by hashing of an inode, to serialize orphan list updates of a single
inode, allowing most prelimary work to be done prior to acquiring the mutex.
The mutex is acuqired only during the update of both orphan lists,
reducing its contention.

Here are some of the benchmark results with the changes.

On a 120 core machine,

---------------------------
|             | % increase |
---------------------------
| alltests    |     19.29  |
---------------------------
| custom      |     11.10  |
---------------------------
| disk        |      5.09  |
---------------------------
| fserver     |     12.47  |
---------------------------
| new_dbase   |      7.49  |
---------------------------
| shared      |     16.55  |
---------------------------

On a 80 core machine,

---------------------------
|             | % increase |
---------------------------
| alltests    |     30.09  |
---------------------------
| custom      |     22.66  |
---------------------------
| dbase       |      3.28  |
---------------------------
| disk        |      3.15  |
---------------------------
| fserver     |     24.28  |
---------------------------
| high_systime|      6.79  |
---------------------------
| new_dbase   |      4.63  |
---------------------------
| new_fserver |     28.40  |
---------------------------
| shared      |     20.42  |
---------------------------

On a 8 core machine:

---------------------------
|             | % increase |
---------------------------
| fserver     |      9.11  |
---------------------------
| new_fserver |      3.45  |
---------------------------

For Swingbench dss workload,

-----------------------------------------------------------------------------
| Users      | 100  | 200  | 300  | 400  | 500  | 600  | 700  | 800  |  900 |
-----------------------------------------------------------------------------
| % improve- | 6.15 | 5.49 | 3.13 | 1.06 | 2.31 | 6.29 | 6.50 |-0.6  | 1.72 |
| ment with  |      |      |      |      |      |      |      |      |      |
| out using  |      |      |      |      |      |      |      |      |      |
| /dev/shm   |      |      |      |      |      |      |      |      |      |
-----------------------------------------------------------------------------

Signed-off-by: T. Makphaibulchoke <tmac@hp.com>
---
Changed in v3:
	- Changed patch description
	- Reverted back to using a single mutex, s_ondisk_orphan_mutex, for
	  both on disk and in memory orphan lists serialization.

Changed in v2:
	- New performance data
    	- Fixed problem in v1
    	- No changes in ext4_inode_info size
    	- Used an array of mutexes, indexed by hashing of an inode, to serialize
    	  operations within a single inode
    	- Combined multiple patches into one.
---
 fs/ext4/ext4.h  |   4 +-
 fs/ext4/namei.c | 126 ++++++++++++++++++++++++++++++++++----------------------
 fs/ext4/super.c |  11 ++++-
 3 files changed, 90 insertions(+), 51 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index d3a534f..a348f7c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -77,6 +77,7 @@
 #define EXT4_ERROR_FILE(file, block, fmt, a...)				\
 	ext4_error_file((file), __func__, __LINE__, (block), (fmt), ## a)
 
+#define	EXT4_ORPHAN_OP_BITS	7
 /* data type for block offset of block group */
 typedef int ext4_grpblk_t;
 
@@ -1223,7 +1224,8 @@ struct ext4_sb_info {
 	/* Journaling */
 	struct journal_s *s_journal;
 	struct list_head s_orphan;
-	struct mutex s_orphan_lock;
+	struct mutex s_ondisk_orphan_lock;
+	struct mutex *s_orphan_op_mutex;
 	unsigned long s_resize_flags;		/* Flags indicating if there
 						   is a resizer */
 	unsigned long s_commit_interval;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index d050e04..b062e1e 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -48,6 +48,13 @@
 #define NAMEI_RA_BLOCKS  4
 #define NAMEI_RA_SIZE	     (NAMEI_RA_CHUNKS * NAMEI_RA_BLOCKS)
 
+#define	ORPHAN_OP_INDEX(ext4_i)				\
+	(hash_long((unsigned long)ext4_i, EXT4_ORPHAN_OP_BITS))
+#define	LOCK_EXT4I_ORPHAN(ext4_sb, ext4_i)		\
+	mutex_lock(&ext4_sb->s_orphan_op_mutex[ORPHAN_OP_INDEX(ext4_i)])
+#define	UNLOCK_EXT4I_ORPHAN(ext4_sb, ext4_i)		\
+	mutex_unlock(&ext4_sb->s_orphan_op_mutex[ORPHAN_OP_INDEX(ext4_i)])
+
 static struct buffer_head *ext4_append(handle_t *handle,
 					struct inode *inode,
 					ext4_lblk_t *block)
@@ -2556,8 +2563,8 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
 	if (!EXT4_SB(sb)->s_journal)
 		return 0;
 
-	mutex_lock(&EXT4_SB(sb)->s_orphan_lock);
-	if (!list_empty(&EXT4_I(inode)->i_orphan))
+	LOCK_EXT4I_ORPHAN(EXT4_SB(sb), EXT4_I(inode));
+	if (!list_empty_careful(&EXT4_I(inode)->i_orphan))
 		goto out_unlock;
 
 	/*
@@ -2582,9 +2589,20 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
 	 * orphan list. If so skip on-disk list modification.
 	 */
 	if (NEXT_ORPHAN(inode) && NEXT_ORPHAN(inode) <=
-		(le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count)))
-			goto mem_insert;
-
+		(le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))) {
+			brelse(iloc.bh);
+			mutex_lock(&EXT4_SB(sb)->s_ondisk_orphan_lock);
+			list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->
+				s_orphan);
+			mutex_unlock(&EXT4_SB(sb)->s_ondisk_orphan_lock);
+			jbd_debug(4, "superblock will point to %lu\n",
+				inode->i_ino);
+			jbd_debug(4, "orphan inode %lu will point to %d\n",
+				inode->i_ino, NEXT_ORPHAN(inode));
+			goto out_unlock;
+	}
+
+	mutex_lock(&EXT4_SB(sb)->s_ondisk_orphan_lock);
 	/* Insert this inode at the head of the on-disk orphan list... */
 	NEXT_ORPHAN(inode) = le32_to_cpu(EXT4_SB(sb)->s_es->s_last_orphan);
 	EXT4_SB(sb)->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
@@ -2592,24 +2610,24 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
 	rc = ext4_mark_iloc_dirty(handle, inode, &iloc);
 	if (!err)
 		err = rc;
-
-	/* Only add to the head of the in-memory list if all the
-	 * previous operations succeeded.  If the orphan_add is going to
-	 * fail (possibly taking the journal offline), we can't risk
-	 * leaving the inode on the orphan list: stray orphan-list
-	 * entries can cause panics at unmount time.
-	 *
-	 * This is safe: on error we're going to ignore the orphan list
-	 * anyway on the next recovery. */
-mem_insert:
-	if (!err)
+	if (!err) {
+		/* Only add to the head of the in-memory list if all the
+		 * previous operations succeeded.  If the orphan_add is going to
+		 * fail (possibly taking the journal offline), we can't risk
+		 * leaving the inode on the orphan list: stray orphan-list
+		 * entries can cause panics at unmount time.
+		 *
+		 * This is safe: on error we're going to ignore the orphan list
+		 * anyway on the next recovery. */
 		list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);
-
-	jbd_debug(4, "superblock will point to %lu\n", inode->i_ino);
-	jbd_debug(4, "orphan inode %lu will point to %d\n",
+		jbd_debug(4, "superblock will point to %lu\n", inode->i_ino);
+		jbd_debug(4, "orphan inode %lu will point to %d\n",
 			inode->i_ino, NEXT_ORPHAN(inode));
+	}
+	mutex_unlock(&EXT4_SB(sb)->s_ondisk_orphan_lock);
+
 out_unlock:
-	mutex_unlock(&EXT4_SB(sb)->s_orphan_lock);
+	UNLOCK_EXT4I_ORPHAN(EXT4_SB(sb), EXT4_I(inode));
 	ext4_std_error(inode->i_sb, err);
 	return err;
 }
@@ -2622,45 +2640,54 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
 {
 	struct list_head *prev;
 	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_sb_info *sbi;
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	__u32 ino_next;
 	struct ext4_iloc iloc;
 	int err = 0;
 
-	if ((!EXT4_SB(inode->i_sb)->s_journal) &&
-	    !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS))
+	if ((!sbi->s_journal) &&
+		!(sbi->s_mount_state & EXT4_ORPHAN_FS))
 		return 0;
 
-	mutex_lock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
-	if (list_empty(&ei->i_orphan))
-		goto out;
-
-	ino_next = NEXT_ORPHAN(inode);
-	prev = ei->i_orphan.prev;
-	sbi = EXT4_SB(inode->i_sb);
-
-	jbd_debug(4, "remove inode %lu from orphan list\n", inode->i_ino);
+	LOCK_EXT4I_ORPHAN(sbi, ei);
+	if (list_empty_careful(&ei->i_orphan)) {
+		UNLOCK_EXT4I_ORPHAN(sbi, ei);
+		return 0;
+	}
 
-	list_del_init(&ei->i_orphan);
 
 	/* If we're on an error path, we may not have a valid
 	 * transaction handle with which to update the orphan list on
 	 * disk, but we still need to remove the inode from the linked
 	 * list in memory. */
-	if (!handle)
-		goto out;
+	if (!handle) {
+		jbd_debug(4, "remove inode %lu from orphan list\n",
+			inode->i_ino);
+		mutex_lock(&sbi->s_ondisk_orphan_lock);
+		list_del_init(&ei->i_orphan);
+		mutex_unlock(&sbi->s_ondisk_orphan_lock);
+	} else
+		err = ext4_reserve_inode_write(handle, inode, &iloc);
 
-	err = ext4_reserve_inode_write(handle, inode, &iloc);
-	if (err)
-		goto out_err;
+	if (!handle || err) {
+		UNLOCK_EXT4I_ORPHAN(sbi, ei);
+		goto out_set_err;
+	}
 
+	mutex_lock(&sbi->s_ondisk_orphan_lock);
+	ino_next = NEXT_ORPHAN(inode);
+	prev = ei->i_orphan.prev;
+	jbd_debug(4, "remove inode %lu from orphan list\n", inode->i_ino);
+	list_del_init(&ei->i_orphan);
 	if (prev == &sbi->s_orphan) {
 		jbd_debug(4, "superblock will point to %u\n", ino_next);
 		BUFFER_TRACE(sbi->s_sbh, "get_write_access");
 		err = ext4_journal_get_write_access(handle, sbi->s_sbh);
+		if (!err)
+			sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
+		mutex_unlock(&sbi->s_ondisk_orphan_lock);
 		if (err)
-			goto out_brelse;
-		sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
+			goto brelse;
 		err = ext4_handle_dirty_super(handle, inode->i_sb);
 	} else {
 		struct ext4_iloc iloc2;
@@ -2670,25 +2697,26 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
 		jbd_debug(4, "orphan inode %lu will point to %u\n",
 			  i_prev->i_ino, ino_next);
 		err = ext4_reserve_inode_write(handle, i_prev, &iloc2);
+		if (!err)
+			NEXT_ORPHAN(i_prev) = ino_next;
+		mutex_unlock(&sbi->s_ondisk_orphan_lock);
 		if (err)
-			goto out_brelse;
-		NEXT_ORPHAN(i_prev) = ino_next;
+			goto brelse;
 		err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
 	}
 	if (err)
-		goto out_brelse;
+		goto brelse;
 	NEXT_ORPHAN(inode) = 0;
+	UNLOCK_EXT4I_ORPHAN(sbi, ei);
 	err = ext4_mark_iloc_dirty(handle, inode, &iloc);
-
-out_err:
+out_set_err:
 	ext4_std_error(inode->i_sb, err);
-out:
-	mutex_unlock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
 	return err;
 
-out_brelse:
+brelse:
+	UNLOCK_EXT4I_ORPHAN(sbi, ei);
 	brelse(iloc.bh);
-	goto out_err;
+	goto out_set_err;
 }
 
 static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 710fed2..a4275d1 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3921,7 +3921,16 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	memcpy(sb->s_uuid, es->s_uuid, sizeof(es->s_uuid));
 
 	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
-	mutex_init(&sbi->s_orphan_lock);
+	mutex_init(&sbi->s_ondisk_orphan_lock);
+	sbi->s_orphan_op_mutex = kmalloc(sizeof(struct mutex) <<
+		EXT4_ORPHAN_OP_BITS, GFP_KERNEL);
+	BUG_ON(!sbi->s_orphan_op_mutex);
+	if (sbi->s_orphan_op_mutex) {
+		int n = 1 << EXT4_ORPHAN_OP_BITS;
+
+		while (n-- > 0)
+			mutex_init(&sbi->s_orphan_op_mutex[n]);
+	}
 
 	sb->s_root = NULL;
 
-- 
1.7.11.3