[CC += linux-api@]
On Mon, Feb 2, 2015 at 6:37 AM, Theodore Ts'o <tytso@xxxxxxx> wrote:
> Add a new function find_inode_nowait() which is an even more general
> version of ilookup5_nowait(). It is designed for callers which need
> very fine grained control over when the function is allowed to block
> or increment the inode's reference count.
>
> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
> ---
> fs/inode.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 5 +++++
> 2 files changed, 55 insertions(+)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 4feb85c..740cba7 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1284,6 +1284,56 @@ struct inode *ilookup(struct super_block *sb, unsigned long ino)
> }
> EXPORT_SYMBOL(ilookup);
>
> +/**
> + * find_inode_nowait - find an inode in the inode cache
> + * @sb: super block of file system to search
> + * @hashval: hash value (usually inode number) to search for
> + * @match: callback used for comparisons between inodes
> + * @data: opaque data pointer to pass to @match
> + *
> + * Search for the inode specified by @hashval and @data in the inode
> + * cache, where the helper function @match will return 0 if the inode
> + * does not match, 1 if the inode does match, and -1 if the search
> + * should be stopped. The @match function must be responsible for
> + * taking the i_lock spin_lock and checking i_state for an inode being
> + * freed or being initialized, and incrementing the reference count
> + * before returning 1. It also must not sleep, since it is called with
> + * the inode_hash_lock spinlock held.
> + *
> + * This is a even more generalized version of ilookup5() when the
> + * function must never block --- find_inode() can block in
> + * __wait_on_freeing_inode() --- or when the caller can not increment
> + * the reference count because the resulting iput() might cause an
> + * inode eviction. The tradeoff is that the @match funtion must be
> + * very carefully implemented.
> + */
> +struct inode *find_inode_nowait(struct super_block *sb,
> + unsigned long hashval,
> + int (*match)(struct inode *, unsigned long,
> + void *),
> + void *data)
> +{
> + struct hlist_head *head = inode_hashtable + hash(sb, hashval);
> + struct inode *inode, *ret_inode = NULL;
> + int mval;
> +
> + spin_lock(&inode_hash_lock);
> + hlist_for_each_entry(inode, head, i_hash) {
> + if (inode->i_sb != sb)
> + continue;
> + mval = match(inode, hashval, data);
> + if (mval == 0)
> + continue;
> + if (mval == 1)
> + ret_inode = inode;
> + goto out;
> + }
> +out:
> + spin_unlock(&inode_hash_lock);
> + return ret_inode;
> +}
> +EXPORT_SYMBOL(find_inode_nowait);
> +
> int insert_inode_locked(struct inode *inode)
> {
> struct super_block *sb = inode->i_sb;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 5ca285f..af810cc 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2441,6 +2441,11 @@ extern struct inode *ilookup(struct super_block *sb, unsigned long ino);
>
> extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
> extern struct inode * iget_locked(struct super_block *, unsigned long);
> +extern struct inode *find_inode_nowait(struct super_block *,
> + unsigned long,
> + int (*match)(struct inode *,
> + unsigned long, void *),
> + void *data);
> extern int insert_inode_locked4(struct inode *, unsigned long, int (*test)(struct inode *, void *), void *);
> extern int insert_inode_locked(struct inode *);
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
> --
> 2.1.0
>
> --
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--
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/
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