[V8,09/11] fs: Introduce DCACHE_DONTCACHE
diff mbox series

Message ID 20200415064523.2244712-10-ira.weiny@intel.com
State New
Headers show
Series
  • Enable per-file/per-directory DAX operations V8
Related show

Commit Message

Ira Weiny April 15, 2020, 6:45 a.m. UTC
From: Ira Weiny <ira.weiny@intel.com>

DCACHE_DONTCACHE indicates a dentry should not be cached on final
dput().

Also add a helper function which will flag I_DONTCACHE as well ad
DCACHE_DONTCACHE on all dentries point to a specified inode.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from V7:
	new patch
---
 fs/dcache.c            |  4 ++++
 fs/inode.c             | 15 +++++++++++++++
 include/linux/dcache.h |  2 ++
 include/linux/fs.h     |  1 +
 4 files changed, 22 insertions(+)

Comments

Jan Kara April 15, 2020, 9:01 a.m. UTC | #1
On Tue 14-04-20 23:45:21, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> DCACHE_DONTCACHE indicates a dentry should not be cached on final
> dput().
> 
> Also add a helper function which will flag I_DONTCACHE as well ad
> DCACHE_DONTCACHE on all dentries point to a specified inode.

I think this sentence needs more work :). Like: Also add a helper function
which will mark the inode with I_DONTCACHE flag and also mark all dentries
pointing to a specified inode as DCACHE_DONTCACHE.

> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> Changes from V7:
> 	new patch
> ---
>  fs/dcache.c            |  4 ++++
>  fs/inode.c             | 15 +++++++++++++++
>  include/linux/dcache.h |  2 ++
>  include/linux/fs.h     |  1 +
>  4 files changed, 22 insertions(+)

...

> diff --git a/fs/inode.c b/fs/inode.c
> index 93d9252a00ab..b8b1917a324e 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 flag_inode_dontcache(struct inode *inode)

mark_inode_dontcache?

> +{
> +	struct dentry *dent;

This is really nitpicking but dentry variables are usually called 'de' or
'dentry' :)

> +
> +	rcu_read_lock();

I don't think this list is safe to traverse under RCU. E.g.
dentry_unlink_inode() does hlist_del_init(&dentry->d_u.d_alias). Usually,
we traverse this list under inode->i_lock protection AFAICS.

								Honza

> +	hlist_for_each_entry(dent, &inode->i_dentry, d_u.d_alias) {
> +		spin_lock(&dent->d_lock);
> +		dent->d_flags |= DCACHE_DONTCACHE;
> +		spin_unlock(&dent->d_lock);
> +	}
> +	rcu_read_unlock();
> +	inode->i_state |= I_DONTCACHE;
> +}
> +EXPORT_SYMBOL(flag_inode_dontcache);
> +
>  /*
>   * Called when we're dropping the last reference
>   * to an inode.
Ira Weiny April 16, 2020, 4:55 a.m. UTC | #2
On Wed, Apr 15, 2020 at 11:01:53AM +0200, Jan Kara wrote:
> On Tue 14-04-20 23:45:21, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> > 
> > DCACHE_DONTCACHE indicates a dentry should not be cached on final
> > dput().
> > 
> > Also add a helper function which will flag I_DONTCACHE as well ad
> > DCACHE_DONTCACHE on all dentries point to a specified inode.
> 
> I think this sentence needs more work :). Like: Also add a helper function
> which will mark the inode with I_DONTCACHE flag and also mark all dentries
> pointing to a specified inode as DCACHE_DONTCACHE.
> 
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > 
> > ---
> > Changes from V7:
> > 	new patch
> > ---
> >  fs/dcache.c            |  4 ++++
> >  fs/inode.c             | 15 +++++++++++++++
> >  include/linux/dcache.h |  2 ++
> >  include/linux/fs.h     |  1 +
> >  4 files changed, 22 insertions(+)
> 
> ...
> 
> > diff --git a/fs/inode.c b/fs/inode.c
> > index 93d9252a00ab..b8b1917a324e 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 flag_inode_dontcache(struct inode *inode)
> 
> mark_inode_dontcache?

That works.

> 
> > +{
> > +	struct dentry *dent;
> 
> This is really nitpicking but dentry variables are usually called 'de' or
> 'dentry' :)

Easy change.  done.

> 
> > +
> > +	rcu_read_lock();
> 
> I don't think this list is safe to traverse under RCU. E.g.
> dentry_unlink_inode() does hlist_del_init(&dentry->d_u.d_alias). Usually,
> we traverse this list under inode->i_lock protection AFAICS.

Ah...  not sure where I got that.  I thought I found this locked with rcu
somewhere but I obviously got confused.  And I did not even use the rcu version
of the list iterator...  :-(

I'll clean it up, thanks for the review,
Ira

> 
> 								Honza
> 
> > +	hlist_for_each_entry(dent, &inode->i_dentry, d_u.d_alias) {
> > +		spin_lock(&dent->d_lock);
> > +		dent->d_flags |= DCACHE_DONTCACHE;
> > +		spin_unlock(&dent->d_lock);
> > +	}
> > +	rcu_read_unlock();
> > +	inode->i_state |= I_DONTCACHE;
> > +}
> > +EXPORT_SYMBOL(flag_inode_dontcache);
> > +
> >  /*
> >   * Called when we're dropping the last reference
> >   * to an inode.
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR

Patch
diff mbox series

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..b8b1917a324e 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 flag_inode_dontcache(struct inode *inode)
+{
+	struct dentry *dent;
+
+	rcu_read_lock();
+	hlist_for_each_entry(dent, &inode->i_dentry, d_u.d_alias) {
+		spin_lock(&dent->d_lock);
+		dent->d_flags |= DCACHE_DONTCACHE;
+		spin_unlock(&dent->d_lock);
+	}
+	rcu_read_unlock();
+	inode->i_state |= I_DONTCACHE;
+}
+EXPORT_SYMBOL(flag_inode_dontcache);
+
 /*
  * Called when we're dropping the last reference
  * to an inode.
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c1488cc84fd9..56b1482d9223 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -177,6 +177,8 @@  struct dentry_operations {
 
 #define DCACHE_REFERENCED		0x00000040 /* Recently used, don't discard. */
 
+#define DCACHE_DONTCACHE		0x00000080 /* don't cache on final dput() */
+
 #define DCACHE_CANT_MOUNT		0x00000100
 #define DCACHE_GENOCIDE			0x00000200
 #define DCACHE_SHRINK_LIST		0x00000400
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e2db71d150c3..f2916c99616a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3048,6 +3048,7 @@  static inline int generic_drop_inode(struct inode *inode)
 	return !inode->i_nlink || inode_unhashed(inode) ||
 		(inode->i_state & I_DONTCACHE);
 }
+extern void flag_inode_dontcache(struct inode *inode);
 
 extern struct inode *ilookup5_nowait(struct super_block *sb,
 		unsigned long hashval, int (*test)(struct inode *, void *),