[PATCH 05/12] fs: insert_inode_locked2()

Kent Overstreet
2019-06-10T19:15:36Z

New helper for bcachefs, so that when we race inserting an inode we can
atomically grab a ref to the inode already in the inode cache.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
fs/inode.c | 40 ++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 1 +
2 files changed, 41 insertions(+)

diff --git a/fs/inode.c b/fs/inode.c
index 8881dc551f..cc44f345e0 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1479,6 +1479,46 @@ int insert_inode_locked(struct inode *inode)
}
EXPORT_SYMBOL(insert_inode_locked);

+struct inode *insert_inode_locked2(struct inode *inode)
+{
+ struct super_block *sb = inode->i_sb;
+ ino_t ino = inode->i_ino;
+ struct hlist_head *head = inode_hashtable + hash(sb, ino);
+
+ while (1) {
+ struct inode *old = NULL;
+ spin_lock(&inode_hash_lock);
+ hlist_for_each_entry(old, head, i_hash) {
+ if (old->i_ino != ino)
+ continue;
+ if (old->i_sb != sb)
+ continue;
+ spin_lock(&old->i_lock);
+ if (old->i_state & (I_FREEING|I_WILL_FREE)) {
+ spin_unlock(&old->i_lock);
+ continue;
+ }
+ break;
+ }
+ if (likely(!old)) {
+ spin_lock(&inode->i_lock);
+ inode->i_state |= I_NEW | I_CREATING;
+ hlist_add_head(&inode->i_hash, head);
+ spin_unlock(&inode->i_lock);
+ spin_unlock(&inode_hash_lock);
+ return NULL;
+ }
+ __iget(old);
+ spin_unlock(&old->i_lock);
+ spin_unlock(&inode_hash_lock);
+ wait_on_inode(old);
+ if (unlikely(!inode_unhashed(old)))
+ return old;
+ iput(old);
+ }
+}
+EXPORT_SYMBOL(insert_inode_locked2);
+
int insert_inode_locked4(struct inode *inode, unsigned long hashval,
int (*test)(struct inode *, void *), void *data)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a88d994751..d5d12d6981 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3010,6 +3010,7 @@ extern struct inode *find_inode_nowait(struct super_block *,
void *data);
extern int insert_inode_locked4(struct inode *, unsigned long, int (*test)(struct inode *, void *), void *);
extern int insert_inode_locked(struct inode *);
+extern struct inode *insert_inode_locked2(struct inode *);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void lockdep_annotate_inode_mutex_key(struct inode *inode);
#else
--
2.20.1