2022-10-16 13:04:31

by Dawei Li

Subject: [PATCH] erofs: protect s_inodes with s_inode_list_lock

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

base-commit: 8436c4a57bd147b0bd2943ab499bb8368981b9e1

Signed-off-by: Dawei Li <[email protected]>
---
fs/erofs/fscache.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 998cd26a1b3b..bbf5268440df 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -589,15 +589,18 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
struct erofs_domain *domain = EROFS_SB(sb)->domain;
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);
- mutex_unlock(&erofs_domain_cookies_lock);
+ spin_unlock(&psb->s_inode_list_lock);
return ctx;
}
+ spin_unlock(&psb->s_inode_list_lock);
+
+ mutex_lock(&erofs_domain_cookies_lock);
ctx = erofs_fscache_domain_init_cookie(sb, name, need_inode);
mutex_unlock(&erofs_domain_cookies_lock);
return ctx;
--
2.25.1

2022-10-16 15:22:46

by Jia Zhu

Subject: Re: [External] [PATCH] erofs: protect s_inodes with s_inode_list_lock

在 2022/10/16 20:37, Dawei Li 写道:
> s_inodes is superblock-specific resource, which should be
> protected by sb's specific lock s_inode_list_lock.
> > base-commit: 8436c4a57bd147b0bd2943ab499bb8368981b9e1
>
> Signed-off-by: Dawei Li <[email protected]>
> ---
> fs/erofs/fscache.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 998cd26a1b3b..bbf5268440df 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -589,15 +589,18 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
> struct erofs_domain *domain = EROFS_SB(sb)->domain;
> struct super_block *psb = erofs_pseudo_mnt->mnt_sb;
>
> - mutex_lock(&erofs_domain_cookies_lock);
Hi Dawei,
Thanks for catching this.

I would suggest holding this mutex lock during inode searches and
inserts to avoid the following case:

P1 P2
lock inode_list lock
traverse sb->s_inodes
unlock inode_list lock
lock inode_list
traverse sb->s_inodes
unlock inode_list
domain_init_cookie
domain_init_cookie

Thanks,
Jia
> + 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);
> - mutex_unlock(&erofs_domain_cookies_lock);
> + spin_unlock(&psb->s_inode_list_lock);
> return ctx;
> }
> + spin_unlock(&psb->s_inode_list_lock);
> +
> + mutex_lock(&erofs_domain_cookies_lock);
> ctx = erofs_fscache_domain_init_cookie(sb, name, need_inode);
> mutex_unlock(&erofs_domain_cookies_lock);
> return ctx;