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Date: Thu, 6 Oct 2011 15:20:37 -0700 (PDT)
From: Sage Weil <sage@...dream.net>
To: Christoph Hellwig <hch@...radead.org>
cc: linux-fsdevel@...r.kernel.org, viro@...IV.linux.org.uk,
ceph-devel@...r.kernel.org, rwheeler@...hat.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: add d_prune dentry operation
On Thu, 6 Oct 2011, Christoph Hellwig wrote:
> On Wed, Oct 05, 2011 at 09:26:10PM -0700, Sage Weil wrote:
> > This adds a d_prune dentry operation that is called by the VFS prior to
> > pruning (i.e. unhashing and killing) a hashed dentry from the dcache. This
> > will be used by Ceph to maintain a flag indicating whether the complete
> > contents of a directory are contained in the dcache, allowing it to satisfy
> > lookups and readdir without addition server communication.
>
> What tree is the patch against? I seems to fail to apply against Linus'
> latests.
Whoops, I rebased against v3.0 instead of latest master.
> It also seem like it basically should not be be opencoded but in a
> wrapper around dentry_lru_del for all cases but the lazy removal from
> LRU in case that is referenced, with some comments explaining the whole
> thing.
Yeah, that's a bit better. There are four dentry_lru_del() callers, two
where we there is a reference, and two where we want to ->d_prune too.
How does the below look?
Thanks!
sage
>From 182e20331b9b2be15dbecdff7465be26ac00a81c Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@...dream.net>
Date: Thu, 6 Oct 2011 15:18:21 -0700
Subject: [PATCH] vfs: add d_prune dentry operation
This adds a d_prune dentry operation that is called by the VFS prior to
pruning (i.e. unhashing and killing) a hashed dentry from the dcache.
Wrap dentry_lru_del() and use the new _prune() helper in the cases where we
are about to unhash and kill the dentry.
This will be used by Ceph to maintain a flag indicating whether the
complete contents of a directory are contained in the dcache, allowing it
to satisfy lookups and readdir without addition server communication.
Signed-off-by: Sage Weil <sage@...dream.net>
---
Documentation/filesystems/Locking | 1 +
fs/dcache.c | 33 ++++++++++++++++++++++++++++-----
include/linux/dcache.h | 3 +++
3 files changed, 32 insertions(+), 5 deletions(-)
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 6533807..d819ba1 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -29,6 +29,7 @@ d_hash no no no maybe
d_compare: yes no no maybe
d_delete: no yes no no
d_release: no no yes no
+d_prune: no yes no no
d_iput: no no yes no
d_dname: no no no no
d_automount: no no yes no
diff --git a/fs/dcache.c b/fs/dcache.c
index a88948b..a348f64 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -225,7 +225,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
}
/*
- * dentry_lru_(add|del|move_tail) must be called with d_lock held.
+ * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
*/
static void dentry_lru_add(struct dentry *dentry)
{
@@ -254,6 +254,24 @@ static void dentry_lru_del(struct dentry *dentry)
}
}
+static void dentry_lru_prune(struct dentry *dentry)
+{
+ if (!list_empty(&dentry->d_lru)) {
+ /*
+ * Notify the fs this dentry is about to be pruned
+ * before removing from the LRU. This should happen
+ * before we unhash it (if it was hashed to begin
+ * with).
+ */
+ if (dentry->d_flags & DCACHE_OP_PRUNE)
+ dentry->d_op->d_prune(dentry);
+
+ spin_lock(&dcache_lru_lock);
+ __dentry_lru_del(dentry);
+ spin_unlock(&dcache_lru_lock);
+ }
+}
+
static void dentry_lru_move_tail(struct dentry *dentry)
{
spin_lock(&dcache_lru_lock);
@@ -403,8 +421,11 @@ relock:
if (ref)
dentry->d_count--;
- /* if dentry was on the d_lru list delete it from there */
- dentry_lru_del(dentry);
+ /*
+ * if dentry was on the d_lru list delete it from there and
+ * inform the fs via d_prune.
+ */
+ dentry_lru_prune(dentry);
/* if it was on the hash then remove it */
__d_drop(dentry);
return d_kill(dentry, parent);
@@ -854,8 +875,8 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
do {
struct inode *inode;
- /* detach from the system */
- dentry_lru_del(dentry);
+ /* detach from the system, inform the fs via d_prune */
+ dentry_lru_prune(dentry);
__d_shrink(dentry);
if (dentry->d_count != 0) {
@@ -1283,6 +1304,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
dentry->d_flags |= DCACHE_OP_REVALIDATE;
if (op->d_delete)
dentry->d_flags |= DCACHE_OP_DELETE;
+ if (op->d_prune)
+ dentry->d_flags |= DCACHE_OP_PRUNE;
}
EXPORT_SYMBOL(d_set_d_op);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 62157c0..69ee43a 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -165,6 +165,7 @@ struct dentry_operations {
unsigned int, const char *, const struct qstr *);
int (*d_delete)(const struct dentry *);
void (*d_release)(struct dentry *);
+ void (*d_prune)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
@@ -216,6 +217,8 @@ struct dentry_operations {
#define DCACHE_MANAGED_DENTRY \
(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
+#define DCACHE_OP_PRUNE 0x80000
+
extern seqlock_t rename_lock;
static inline int dname_external(struct dentry *dentry)
--
1.7.0
--
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