diff mbox series

[V9,09/11] fs: Introduce DCACHE_DONTCACHE

Message ID 20200421191754.3372370-10-ira.weiny@intel.com
State Not Applicable
Headers show
Series XFS - Enable per-file/per-directory DAX operations V9 | expand

Commit Message

Ira Weiny April 21, 2020, 7:17 p.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 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@zeniv.linux.org.uk>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
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(-)

Comments

Darrick Wong April 21, 2020, 8:25 p.m. UTC | #1 
On Tue, Apr 21, 2020 at 12:17:51PM -0700, 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 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@zeniv.linux.org.uk>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> 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;
> +}
> +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));
>  	ip->i_udquot = NULL;
>  	ip->i_gdquot = NULL;
>  	ip->i_pdquot = NULL;
> 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() */

"Purge from memory on final dput()"?

--D

> +
>  #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 44bd45af760f..064168ec2e0b 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3055,6 +3055,7 @@ static inline int generic_drop_inode(struct inode *inode)
>  	return !inode->i_nlink || inode_unhashed(inode) ||
>  		(inode->i_state & I_DONTCACHE);
>  }
> +extern void mark_inode_dontcache(struct inode *inode);
>  
>  extern struct inode *ilookup5_nowait(struct super_block *sb,
>  		unsigned long hashval, int (*test)(struct inode *, void *),
> -- 
> 2.25.1
>
Ira Weiny April 21, 2020, 9:15 p.m. UTC | #2 
On Tue, Apr 21, 2020 at 01:25:19PM -0700, Darrick J. Wong wrote:
> On Tue, Apr 21, 2020 at 12:17:51PM -0700, 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 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@zeniv.linux.org.uk>
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > 
> > ---

[snip]

> > 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));
> >  	ip->i_udquot = NULL;
> >  	ip->i_gdquot = NULL;
> >  	ip->i_pdquot = NULL;
> > 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() */
> 
> "Purge from memory on final dput()"?

Sounds good to me,
Ira

> 
> --D
>
Al Viro April 22, 2020, 2:34 a.m. UTC | #3 
On Tue, Apr 21, 2020 at 01:25:19PM -0700, Darrick J. Wong wrote:

> > 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.

Explain, please.  Questions:

1) does that ever happen to directories?
2) how much trouble do we get if such inode is *NOT* evicted for, say, several
days?
Ira Weiny April 22, 2020, 3:46 a.m. UTC | #4 
On Wed, Apr 22, 2020 at 03:34:07AM +0100, Al Viro wrote:
> On Tue, Apr 21, 2020 at 01:25:19PM -0700, Darrick J. Wong wrote:
> 
> > > 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.
> 
> Explain, please.  Questions:
> 
> 1) does that ever happen to directories?

Directories never get S_DAX set.  So the eviction only needs to happen on
inodes.  But that can't happen without dentries also dropping their references.

> 2) how much trouble do we get if such inode is *NOT* evicted for, say, several
> days?

No trouble at all.  Users understand that changing the FS_XFLAG_DAX setting
does _not_ immediately result in S_DAX changing.

It is intended that applications requiring a change of mode would flip the
FS_XFLAG_DAX close the file and wait for the eviction (or force it through a
drop cache if they have permission).

Ira
Jan Kara April 22, 2020, 8:46 a.m. UTC | #5 
On Tue 21-04-20 12:17:51, 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 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@zeniv.linux.org.uk>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> 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
Ira Weiny April 22, 2020, 3:19 p.m. UTC | #6 
On Wed, Apr 22, 2020 at 10:46:47AM +0200, Jan Kara wrote:
> On Tue 21-04-20 12:17:51, 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 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@zeniv.linux.org.uk>
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > 
> > ---
> > 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@suse.com>
> SUSE Labs, CR
diff mbox series

Patch

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;
+}
+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));
 	ip->i_udquot = NULL;
 	ip->i_gdquot = NULL;
 	ip->i_pdquot = NULL;
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 44bd45af760f..064168ec2e0b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3055,6 +3055,7 @@  static inline int generic_drop_inode(struct inode *inode)
 	return !inode->i_nlink || inode_unhashed(inode) ||
 		(inode->i_state & I_DONTCACHE);
 }
+extern void mark_inode_dontcache(struct inode *inode);
 
 extern struct inode *ilookup5_nowait(struct super_block *sb,
 		unsigned long hashval, int (*test)(struct inode *, void *),