On Wed, Apr 22, 2020 at 10:46:47AM +0200, Jan Kara wrote:
> 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.
Done.
>
> > +}
> > +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.
Thanks!
Ira
>
> Honza
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
