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Message-Id: <E1P8ERs-0006k4-Gz@pomaz-ex.szeredi.hu>
Date: Tue, 19 Oct 2010 17:50:00 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: npiggin@...nel.dk
CC: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [patch 26/35] fs: icache alloc anonymous inode allocation
On Tue, 19 Oct 2010, npiggin@...nel.d wrote:
> Provide new_anon_inode function for inodes without a default inode number, and
> not on sb list. This can enable filesystems to reduce locking. "Real"
> filesystems can also reduce locking by allocating anonymous inode first, then
> adding it to lists after finding the inode number.
>
> Signed-off-by: Nick Piggin <npiggin@...nel.dk>
>
> ---
> fs/anon_inodes.c | 2 +-
> fs/inode.c | 32 +++++++++++++++++++++++++++++++-
> fs/pipe.c | 3 ++-
> include/linux/fs.h | 2 ++
> net/socket.c | 3 ++-
> 5 files changed, 38 insertions(+), 4 deletions(-)
>
> Index: linux-2.6/fs/inode.c
> ===================================================================
> --- linux-2.6.orig/fs/inode.c 2010-10-19 14:18:59.000000000 +1100
> +++ linux-2.6/fs/inode.c 2010-10-19 14:19:22.000000000 +1100
> @@ -219,6 +219,7 @@
> #ifdef CONFIG_QUOTA
> memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
> #endif
> + INIT_LIST_HEAD(&inode->i_sb_list);
> inode->i_pipe = NULL;
> inode->i_bdev = NULL;
> inode->i_cdev = NULL;
> @@ -761,6 +762,8 @@
> */
> static void inode_sb_list_del(struct inode *inode)
> {
> + if (list_empty(&inode->i_sb_list))
> + return;
> lg_local_lock_cpu(inode_list_lglock, inode_list_cpu(inode));
> list_del_rcu(&inode->i_sb_list);
> lg_local_unlock_cpu(inode_list_lglock, inode_list_cpu(inode));
> @@ -819,7 +822,7 @@
> */
> static DEFINE_PER_CPU(unsigned int, last_ino);
>
> -static unsigned int get_next_ino(void)
> +unsigned int get_next_ino(void)
> {
> unsigned int res;
>
> @@ -838,6 +841,7 @@
> put_cpu();
> return res;
> }
> +EXPORT_SYMBOL(get_next_ino);
>
> /**
> * new_inode - obtain an inode
> @@ -870,6 +874,32 @@
> }
> EXPORT_SYMBOL(new_inode);
>
> +/**
> + * new_anon_inode - obtain an anonymous inode
> + * @sb: superblock
> + *
> + * Similar to new_inode, however the inode is not given an inode
> + * number, and is not added to the sb's list of inodes, to reduce
> + * overheads.
> + *
> + * A filesystem which needs an inode number must subsequently
> + * assign one to i_ino. A filesystem which needs inodes to be on the
> + * per-sb list (currently only used by the vfs for umount or remount)
> + * must add the inode to that list.
> + */
> +struct inode *new_anon_inode(struct super_block *sb)
> +{
> + struct inode *inode;
> +
> + inode = alloc_inode(sb);
> + if (inode) {
> + inode->i_ino = ULONG_MAX;
> + inode->i_state = 0;
> + }
> + return inode;
> +}
> +EXPORT_SYMBOL(new_anon_inode);
> +
> void unlock_new_inode(struct inode *inode)
> {
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
> Index: linux-2.6/fs/pipe.c
> ===================================================================
> --- linux-2.6.orig/fs/pipe.c 2010-10-19 14:18:59.000000000 +1100
> +++ linux-2.6/fs/pipe.c 2010-10-19 14:19:00.000000000 +1100
> @@ -948,7 +948,7 @@
>
> static struct inode * get_pipe_inode(void)
> {
> - struct inode *inode = new_inode(pipe_mnt->mnt_sb);
> + struct inode *inode = new_anon_inode(pipe_mnt->mnt_sb);
> struct pipe_inode_info *pipe;
>
> if (!inode)
> @@ -962,6 +962,7 @@
> pipe->readers = pipe->writers = 1;
> inode->i_fop = &rdwr_pipefifo_fops;
>
> + inode->i_ino = get_next_ino();
> /*
> * Mark the inode dirty from the very beginning,
> * that way it will never be moved to the dirty
> Index: linux-2.6/include/linux/fs.h
> ===================================================================
> --- linux-2.6.orig/include/linux/fs.h 2010-10-19 14:18:59.000000000 +1100
> +++ linux-2.6/include/linux/fs.h 2010-10-19 14:19:21.000000000 +1100
> @@ -2192,11 +2192,13 @@
> extern int insert_inode_locked(struct inode *);
> extern void unlock_new_inode(struct inode *);
>
> +extern unsigned int get_next_ino(void);
> extern void iget_failed(struct inode *);
> extern void end_writeback(struct inode *);
> extern void destroy_inode(struct inode *);
> extern void __destroy_inode(struct inode *);
> extern struct inode *new_inode(struct super_block *);
> +extern struct inode *new_anon_inode(struct super_block *);
> extern void free_inode_nonrcu(struct inode *inode);
> extern int should_remove_suid(struct dentry *);
> extern int file_remove_suid(struct file *);
> Index: linux-2.6/net/socket.c
> ===================================================================
> --- linux-2.6.orig/net/socket.c 2010-10-19 14:18:59.000000000 +1100
> +++ linux-2.6/net/socket.c 2010-10-19 14:19:19.000000000 +1100
> @@ -476,13 +476,14 @@
> struct inode *inode;
> struct socket *sock;
>
> - inode = new_inode(sock_mnt->mnt_sb);
> + inode = new_anon_inode(sock_mnt->mnt_sb);
> if (!inode)
> return NULL;
>
> sock = SOCKET_I(inode);
>
> kmemcheck_annotate_bitfield(sock, type);
> + inode->i_ino = get_next_ino();
> inode->i_mode = S_IFSOCK | S_IRWXUGO;
> inode->i_uid = current_fsuid();
> inode->i_gid = current_fsgid();
> Index: linux-2.6/fs/anon_inodes.c
> ===================================================================
> --- linux-2.6.orig/fs/anon_inodes.c 2010-10-19 14:18:58.000000000 +1100
> +++ linux-2.6/fs/anon_inodes.c 2010-10-19 14:19:19.000000000 +1100
> @@ -191,7 +191,7 @@
> */
> static struct inode *anon_inode_mkinode(void)
> {
> - struct inode *inode = new_inode(anon_inode_mnt->mnt_sb);
> + struct inode *inode = new_anon_inode(anon_inode_mnt->mnt_sb);
>
> if (!inode)
> return ERR_PTR(-ENOMEM);
This too needs an inode->i_ino initialization (the default ULONG_MAX
will cause EOVERFLOW on 32bit fstat, AFAIK), though it could just be a
constant, say 2.
Miklos
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