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 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
--
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