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SubjectRe: [PATCH] vfs: dont chain pipe/anon/socket on superblock s_inodes list
On Tue, Jul 26, 2011 at 10:21:06AM +0200, Eric Dumazet wrote:
> Well, not 'last' contention point, as we still hit remove_inode_hash(),

There should be no ned to put pipe or anon inodes on the inode hash.
Probably sockets don't need it either, but I'd need to look at it in
detail.

> inode_wb_list_del()

The should never be on the wb list either, doing an unlocked check for
actually beeing on the list before taking the lock should help you.

> inode_lru_list_del(),

No real need to keep inodes in the LRU if we only allocate them using
new_inode but never look them up either. You might want to try setting
.drop_inode to generic_delete_inode for these.

> +struct inode *__new_inode(struct super_block *sb)
> +{
> + struct inode *inode = alloc_inode(sb);
> +
> + if (inode) {
> + spin_lock(&inode->i_lock);
> + inode->i_state = 0;
> + spin_unlock(&inode->i_lock);
> + INIT_LIST_HEAD(&inode->i_sb_list);
> + }
> + return inode;
> +}

This needs a much better name like new_inode_pseudo, and a kerneldoc
comment explaining when it is safe to use, and the consequences, which
appear to me:

- fs may never be unmount
- quotas can't work on the filesystem
- writeback can't work on the filesystem

> @@ -814,13 +829,9 @@ struct inode *new_inode(struct super_block *sb)
>
> spin_lock_prefetch(&inode_sb_list_lock);
>
> - inode = alloc_inode(sb);
> - if (inode) {
> - spin_lock(&inode->i_lock);
> - inode->i_state = 0;
> - spin_unlock(&inode->i_lock);
> - inode_sb_list_add(inode);
> - }
> + inode = __new_inode(sb);
> + if (inode)
> + inode_sb_list_add(inode);

bad indentation.



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