On Tue 21-04-20 12:17:51, ira.weiny@xxxxxxxxx wrote:
> From: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> DCACHE_DONTCACHE indicates a dentry should not be cached on final
> dput().
>
> Also add a helper function to mark DCACHE_DONTCACHE on all dentries
> pointing to a specific inode when that inode is being set I_DONTCACHE.
>
> This facilitates dropping dentry references to inodes sooner which
> require eviction to swap S_DAX mode.
>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> ---
> Changes from V8:
> Update commit message
> Use mark_inode_dontcache in XFS
> Fix locking... can't use rcu here.
> Change name to mark_inode_dontcache
> ---
> fs/dcache.c | 4 ++++
> fs/inode.c | 15 +++++++++++++++
> fs/xfs/xfs_icache.c | 2 +-
> include/linux/dcache.h | 2 ++
> include/linux/fs.h | 1 +
> 5 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index b280e07e162b..0030fabab2c4 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -647,6 +647,10 @@ static inline bool retain_dentry(struct dentry *dentry)
> if (dentry->d_op->d_delete(dentry))
> return false;
> }
> +
> + if (unlikely(dentry->d_flags & DCACHE_DONTCACHE))
> + return false;
> +
> /* retain; LRU fodder */
> dentry->d_lockref.count--;
> if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
> diff --git a/fs/inode.c b/fs/inode.c
> index 93d9252a00ab..da7f3c4926cd 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1526,6 +1526,21 @@ int generic_delete_inode(struct inode *inode)
> }
> EXPORT_SYMBOL(generic_delete_inode);
>
> +void mark_inode_dontcache(struct inode *inode)
> +{
> + struct dentry *de;
> +
> + spin_lock(&inode->i_lock);
> + hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
> + spin_lock(&de->d_lock);
> + de->d_flags |= DCACHE_DONTCACHE;
> + spin_unlock(&de->d_lock);
> + }
> + spin_unlock(&inode->i_lock);
> + inode->i_state |= I_DONTCACHE;
Modification of i_state should happen under i_lock.
> +}
> +EXPORT_SYMBOL(mark_inode_dontcache);
> +
> /*
> * Called when we're dropping the last reference
> * to an inode.
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index de76f7f60695..3c8f44477804 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -559,7 +559,7 @@ xfs_iget_cache_miss(
> */
> iflags = XFS_INEW;
> if (flags & XFS_IGET_DONTCACHE)
> - VFS_I(ip)->i_state |= I_DONTCACHE;
> + mark_inode_dontcache(VFS_I(ip));
And I know here modification of i_state didn't happen under i_lock but
that's a special case because we are just instantiating the inode so it was
not a real issue.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
