回复:[RFC PATCH v3 09/10] ovl: introduce helper of syncfs writeback inode waiting

[Chengguang Xu <cgxu519@mykernel.net>]

 ---- 在 星期日, 2020-11-08 22:03:06 Chengguang Xu <cgxu519@mykernel.net> 撰写 ----
 > Introduce a helper ovl_wait_wb_inodes() to wait until all
 > target upper inodes finish writeback.
 > 
 > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
 > ---
 >  fs/overlayfs/super.c | 30 ++++++++++++++++++++++++++++++
 >  1 file changed, 30 insertions(+)
 > 
 > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
 > index e5607a908d82..9a535fc11221 100644
 > --- a/fs/overlayfs/super.c
 > +++ b/fs/overlayfs/super.c
 > @@ -255,6 +255,36 @@ static void ovl_put_super(struct super_block *sb)
 >      ovl_free_fs(ofs);
 >  }
 >  
 > +void ovl_wait_wb_inodes(struct ovl_fs *ofs)
 > +{
 > +    LIST_HEAD(tmp_list);
 > +    struct ovl_inode *oi;
 > +    struct inode *upper;
 > +
 > +    spin_lock(&ofs->syncfs_wait_list_lock);
 > +    list_splice_init(&ofs->syncfs_wait_list, &tmp_list);
 > +
 > +    while (!list_empty(&tmp_list)) {
 > +        oi = list_first_entry(&tmp_list, struct ovl_inode, wait_list);
 > +        list_del_init(&oi->wait_list);
 > +        ihold(&oi->vfs_inode);

Maybe I overlooked race condition with inode eviction, so still need to introduce
OVL_EVICT_PENDING flag just like we did in old syncfs efficiency patch series.


Thanks，
Chengguang