[PATCH v2] erofs: protect s_inodes with s_inode_list_lock

[Dawei Li]

s_inodes is superblock-specific resource, which should be
protected by sb's specific lock s_inode_list_lock.

v2: update the locking mechanisim to protect mutual-exclusive access
both for s_inode_list_lock & erofs_fscache_domain_init_cookie(), as the
reviewing comments from Jia Zhu.

v1: https://lore.kernel.org/all/TYCP286MB23237A9993E0FFCFE5C2BDBECA269@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/

base-commit: 8436c4a57bd147b0bd2943ab499bb8368981b9e1

Signed-off-by: Dawei Li <set_pte_at at outlook.com>
---
 fs/erofs/fscache.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 998cd26a1b3b..fe05bc51f9f2 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -590,14 +590,17 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
 	struct super_block *psb = erofs_pseudo_mnt->mnt_sb;
 
 	mutex_lock(&erofs_domain_cookies_lock);
+	spin_lock(&psb->s_inode_list_lock);
 	list_for_each_entry(inode, &psb->s_inodes, i_sb_list) {
 		ctx = inode->i_private;
 		if (!ctx || ctx->domain != domain || strcmp(ctx->name, name))
 			continue;
 		igrab(inode);
+		spin_unlock(&psb->s_inode_list_lock);
 		mutex_unlock(&erofs_domain_cookies_lock);
 		return ctx;
 	}
+	spin_unlock(&psb->s_inode_list_lock);
 	ctx = erofs_fscache_domain_init_cookie(sb, name, need_inode);
 	mutex_unlock(&erofs_domain_cookies_lock);
 	return ctx;
-- 
2.25.1