答复: [????] [PATCH v2 14/17] afs: Remove erroneous seq |= 1 in volume lookup loop

["Li,Rongqing" <lirongqing@baidu.com>]

> 主题: [????] [PATCH v2 14/17] afs: Remove erroneous seq |= 1 in volume lookup
> loop

I think this title is inaccurate

> 
> This is an addendum to the patch to remove the erroneous seq |= 1 in volume
> lookup loop.
> 
> Switch to using scoped_seqlock_read() as suggested by Oleg Nesterov[1].
> 
> Fixes: 32222f09782f ("afs: Apply server breaks to mmap'd files in the call
> processor")

And this Fixes is not needed due to the sixth patch

[Li,Rongqing] 


> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Marc Dionne <marc.dionne@auristor.com>
> cc: Oleg Nesterov <oleg@redhat.com>
> cc: Li RongQing <lirongqing@baidu.com>
> cc: linux-afs@lists.infradead.org
> Link: https://lore.kernel.org/r/aifaeKvz3KemfzaS@redhat.com/ [1]
> ---
>  fs/afs/callback.c | 9 +--------
>  fs/afs/internal.h | 2 --
>  2 files changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/fs/afs/callback.c b/fs/afs/callback.c index
> 833ac3178ddc..dd7a407ea368 100644
> --- a/fs/afs/callback.c
> +++ b/fs/afs/callback.c
> @@ -113,16 +113,12 @@ static struct afs_volume
> *afs_lookup_volume_rcu(struct afs_cell *cell,  {
>  	struct afs_volume *volume = NULL;
>  	struct rb_node *p;
> -	int seq = 1;
> 
> -	for (;;) {
> +	scoped_seqlock_read(&cell->volume_lock, ss_lock) {
>  		/* Unfortunately, rbtree walking doesn't give reliable results
>  		 * under just the RCU read lock, so we have to check for
>  		 * changes.
>  		 */
> -		seq++; /* 2 on the 1st/lockless path, otherwise odd */
> -		read_seqbegin_or_lock(&cell->volume_lock, &seq);
> -
>  		p = rcu_dereference_raw(cell->volumes.rb_node);
>  		while (p) {
>  			volume = rb_entry(p, struct afs_volume, cell_node); @@ -138,11
> +134,8 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell
> *cell,
> 
>  		if (volume && afs_try_get_volume(volume,
> afs_volume_trace_get_callback))
>  			break;
> -		if (!need_seqretry(&cell->volume_lock, seq))
> -			break;
>  	}
> 
> -	done_seqretry(&cell->volume_lock, seq);
>  	return volume;
>  }
> 
> diff --git a/fs/afs/internal.h b/fs/afs/internal.h index
> 0b72a8566299..785c646856d7 100644
> --- a/fs/afs/internal.h
> +++ b/fs/afs/internal.h
> @@ -750,8 +750,6 @@ static inline void afs_vnode_set_cache(struct afs_vnode
> *vnode,  {  #ifdef CONFIG_AFS_FSCACHE
>  	vnode->netfs.cache = cookie;
> -	if (cookie)
> -		mapping_set_release_always(vnode->netfs.inode.i_mapping);
>  #endif
>  }
>