From: Theodore Ts'o Subject: [PATCH-v7 2/3] vfs: add find_inode_nowait() function Date: Mon, 8 Dec 2014 23:04:29 -0500 Message-ID: <1418097870-8232-3-git-send-email-tytso@mit.edu> References: <1418097870-8232-1-git-send-email-tytso@mit.edu> Cc: Ext4 Developers List , Theodore Ts'o To: Linux Filesystem Development List Return-path: Received: from imap.thunk.org ([74.207.234.97]:46558 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754294AbaLIEEh (ORCPT ); Mon, 8 Dec 2014 23:04:37 -0500 In-Reply-To: <1418097870-8232-1-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 --- 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 dc48a23..42d86dd 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -1282,6 +1282,56 @@ 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 bf00e98..dfbba90 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2415,6 +2415,11 @@ 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