fs/9p: use fscache mutex rather than spinlock

BugLink: https://bugs.launchpad.net/bugs/1822271

commit 8f5fed1e upstream.

We may sleep inside a the lock, so use a mutex rather than spinlock.
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Emil Karlson <jkarlson@tuxera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/9p/cache.c

@@ -243,14 +243,14 @@ void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
 	if (!v9inode->fscache)
 		return;
 
-	spin_lock(&v9inode->fscache_lock);
+	mutex_lock(&v9inode->fscache_lock);
 
 	if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 		v9fs_cache_inode_flush_cookie(inode);
 	else
 		v9fs_cache_inode_get_cookie(inode);
 
-	spin_unlock(&v9inode->fscache_lock);
+	mutex_unlock(&v9inode->fscache_lock);
 }
 
 void v9fs_cache_inode_reset_cookie(struct inode *inode)
@@ -264,7 +264,7 @@ void v9fs_cache_inode_reset_cookie(struct inode *inode)
 
 	old = v9inode->fscache;
 
-	spin_lock(&v9inode->fscache_lock);
+	mutex_lock(&v9inode->fscache_lock);
 	fscache_relinquish_cookie(v9inode->fscache, 1);
 
 	v9ses = v9fs_inode2v9ses(inode);
@@ -274,7 +274,7 @@ void v9fs_cache_inode_reset_cookie(struct inode *inode)
 	p9_debug(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p\n",
 		 inode, old, v9inode->fscache);
 
-	spin_unlock(&v9inode->fscache_lock);
+	mutex_unlock(&v9inode->fscache_lock);
 }
 
 int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)

fs/9p/v9fs.h

@@ -123,7 +123,7 @@ struct v9fs_session_info {
 
 struct v9fs_inode {
 #ifdef CONFIG_9P_FSCACHE
-	spinlock_t fscache_lock;
+	struct mutex fscache_lock;
 	struct fscache_cookie *fscache;
 #endif
 	struct p9_qid qid;

fs/9p/vfs_inode.c

@@ -244,7 +244,7 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
 		return NULL;
 #ifdef CONFIG_9P_FSCACHE
 	v9inode->fscache = NULL;
-	spin_lock_init(&v9inode->fscache_lock);
+	mutex_init(&v9inode->fscache_lock);
 #endif
 	v9inode->writeback_fid = NULL;
 	v9inode->cache_validity = 0;