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SubjectRe: [PATCH 2/2] fs/ext4/namei.c: reducing contention on s_orphan_lock mmutex
Hello,

On Wed, Oct 02, 2013 at 09:36:59AM -0600, T Makphaibulchoke wrote:
> Instead of using a single per super block mutex, s_orphan_lock, to serialize
> all orphan list updates, a separate mutex and spinlock are used to
> protect the on disk and in memory orphan lists respecvitely.
>
> At the same time, a per inode mutex is used to serialize orphan list
> updates of a single inode.
>
> Signed-off-by: T. Makphaibulchoke <tmac@hp.com>
> ---
> fs/ext4/namei.c | 139 ++++++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 100 insertions(+), 39 deletions(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 35f55a0..d7d3d0f 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2554,12 +2554,24 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
> struct super_block *sb = inode->i_sb;
> struct ext4_iloc iloc;
> int err = 0, rc;
> + struct ext4_inode_info *ext4_inode = EXT4_I(inode);
> + struct ext4_sb_info *ext4_sb = EXT4_SB(sb);
> + struct mutex *inode_orphan_mutex;
> + spinlock_t *orphan_lock;
> + struct mutex *ondisk_orphan_mutex;
> + struct list_head *prev;
> + unsigned int next_inum;
> + struct inode *next_inode;
>
> - if (!EXT4_SB(sb)->s_journal)
> + if (ext4_sb->s_journal)
^^^^^^^^
typo: !ext4_sb->s_journal
I am not sure whether or not this will impact the result because when
journal is enabled the inode will not be added into orphan list.

Regards,
- Zheng

> return 0;
>
> - mutex_lock(&EXT4_SB(sb)->s_orphan_lock);
> - if (!list_empty(&EXT4_I(inode)->i_orphan))
> + inode_orphan_mutex = &ext4_inode->i_orphan_mutex;
> + orphan_lock = &ext4_sb->s_orphan_lock;
> + ondisk_orphan_mutex = &ext4_sb->s_ondisk_orphan_lock;
> + mutex_lock(inode_orphan_mutex);
> + prev = ext4_inode->i_orphan.prev;
> + if (prev != &ext4_inode->i_orphan)
> goto out_unlock;
>
> /*
> @@ -2579,17 +2591,28 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
> err = ext4_reserve_inode_write(handle, inode, &iloc);
> if (err)
> goto out_unlock;
> + mutex_lock(ondisk_orphan_mutex);
> /*
> * Due to previous errors inode may be already a part of on-disk
> * 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)))
> + (le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))) {
> + mutex_unlock(ondisk_orphan_mutex);
> goto mem_insert;
> + }
>
> /* 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);
> + next_inum = le32_to_cpu(EXT4_SB(sb)->s_es->s_last_orphan);
> + NEXT_ORPHAN(inode) = next_inum;
> + next_inode = ilookup(sb, next_inum);
> + if (next_inode)
> + EXT4_I(next_inode)->i_prev_orphan = inode->i_ino;
> + ext4_sb->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
> + ext4_inode->i_prev_orphan = 0;
> + mutex_unlock(ondisk_orphan_mutex);
> + if (next_inode)
> + iput(next_inode);
> err = ext4_handle_dirty_super(handle, sb);
> rc = ext4_mark_iloc_dirty(handle, inode, &iloc);
> if (!err)
> @@ -2604,14 +2627,17 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
> * This is safe: on error we're going to ignore the orphan list
> * anyway on the next recovery. */
> mem_insert:
> - if (!err)
> - list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);
> + if (!err) {
> + spin_lock(orphan_lock);
> + list_add(&ext4_inode->i_orphan, &ext4_sb->s_orphan);
> + spin_unlock(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));
> out_unlock:
> - mutex_unlock(&EXT4_SB(sb)->s_orphan_lock);
> + mutex_unlock(inode_orphan_mutex);
> ext4_std_error(inode->i_sb, err);
> return err;
> }
> @@ -2624,71 +2650,106 @@ 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 inode *i_next = NULL;
> + struct inode *i_prev = NULL;
> + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> __u32 ino_next;
> + unsigned int ino_prev;
> struct ext4_iloc iloc;
> int err = 0;
> + struct mutex *inode_orphan_mutex;
> + spinlock_t *orphan_lock;
> + struct mutex *ondisk_orphan_mutex;
>
> - 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);
> + inode_orphan_mutex = &ei->i_orphan_mutex;
> + orphan_lock = &sbi->s_orphan_lock;
> + ondisk_orphan_mutex = &sbi->s_ondisk_orphan_lock;
> + mutex_lock(inode_orphan_mutex);
> prev = ei->i_orphan.prev;
> - sbi = EXT4_SB(inode->i_sb);
> + if (prev == &ei->i_orphan) {
> + mutex_unlock(inode_orphan_mutex);
> + return err;
> + }
>
> jbd_debug(4, "remove inode %lu from orphan list\n", inode->i_ino);
>
> + spin_lock(orphan_lock);
> list_del_init(&ei->i_orphan);
> + spin_unlock(orphan_lock);
>
> /* 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) {
> + mutex_unlock(inode_orphan_mutex);
> + return err;
> + }
>
> err = ext4_reserve_inode_write(handle, inode, &iloc);
> - if (err)
> + if (err) {
> + mutex_unlock(inode_orphan_mutex);
> goto out_err;
> + }
>
> - if (prev == &sbi->s_orphan) {
> + mutex_lock(ondisk_orphan_mutex);
> + ino_next = NEXT_ORPHAN(inode);
> + if (ino_next > 0) {
> + i_next = ilookup(inode->i_sb, ino_next);
> + assert(i_next);
> + }
> + ino_prev = ei->i_prev_orphan;
> + if (!ino_prev) {
> 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)
> - goto out_brelse;
> - sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
> - err = ext4_handle_dirty_super(handle, inode->i_sb);
> + if (!err) {
> + sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
> + if (i_next)
> + EXT4_I(i_next)->i_prev_orphan = 0;
> + }
> + mutex_unlock(ondisk_orphan_mutex);
> + if (!err)
> + err = ext4_handle_dirty_super(handle, inode->i_sb);
> } else {
> struct ext4_iloc iloc2;
> - struct inode *i_prev =
> - &list_entry(prev, struct ext4_inode_info, i_orphan)->vfs_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)
> - goto out_brelse;
> - NEXT_ORPHAN(i_prev) = ino_next;
> - err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
> + i_prev = ilookup(inode->i_sb, ino_prev);
> +
> + assert(i_prev);
> + if (i_prev) {
> + 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);
> + } else
> + err = -ENOENT;
> + if (!err) {
> + NEXT_ORPHAN(i_prev) = ino_next;
> + if (i_next)
> + EXT4_I(i_next)->i_prev_orphan = ino_prev;
> + }
> + mutex_unlock(ondisk_orphan_mutex);
> + if (i_prev && !err)
> + err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
> }
> if (err)
> goto out_brelse;
> NEXT_ORPHAN(inode) = 0;
> + mutex_unlock(inode_orphan_mutex);
> err = ext4_mark_iloc_dirty(handle, inode, &iloc);
> -
> out_err:
> + if (i_next)
> + iput(i_next);
> + if (i_prev)
> + iput(i_prev);
> ext4_std_error(inode->i_sb, err);
> -out:
> - mutex_unlock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
> return err;
>
> out_brelse:
> + mutex_unlock(inode_orphan_mutex);
> brelse(iloc.bh);
> goto out_err;
> }
> --
> 1.7.11.3
>
> --
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