fuse: Introduce fi->lock to protect write related fields

To minimize contention of fc->lock, this patch introduces a new spinlock
for protection fuse_inode metadata:

fuse_inode:
	writectr
	writepages
	write_files
	queued_writes
	attr_version

inode:
	i_size
	i_nlink
	i_mtime
	i_ctime

Also, it protects the fields changed in fuse_change_attributes_common()
(too many to list).

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 86e86fcd6267..4c767175bd34 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -97,6 +97,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 	fi->orig_ino = 0;
 	fi->state = 0;
 	mutex_init(&fi->mutex);
+	spin_lock_init(&fi->lock);
 	fi->forget = fuse_alloc_forget();
 	if (!fi->forget) {
 		kmem_cache_free(fuse_inode_cachep, inode);
@@ -163,6 +164,8 @@ void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 
+	lockdep_assert_held(&fi->lock);
+
 	fi->attr_version = atomic64_inc_return(&fc->attr_version);
 	fi->i_time = attr_valid;
 	WRITE_ONCE(fi->inval_mask, 0);
@@ -209,10 +212,10 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
 	loff_t oldsize;
 	struct timespec64 old_mtime;
 
-	spin_lock(&fc->lock);
+	spin_lock(&fi->lock);
 	if ((attr_version != 0 && fi->attr_version > attr_version) ||
 	    test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
-		spin_unlock(&fc->lock);
+		spin_unlock(&fi->lock);
 		return;
 	}
 
@@ -227,7 +230,7 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
 	 */
 	if (!is_wb || !S_ISREG(inode->i_mode))
 		i_size_write(inode, attr->size);
-	spin_unlock(&fc->lock);
+	spin_unlock(&fi->lock);
 
 	if (!is_wb && S_ISREG(inode->i_mode)) {
 		bool inval = false;