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vfs: add d_prune dentry operation

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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.

Renumber a few DCACHE_* #defines to group DCACHE_OP_PRUNE with the other
DCACHE_OP_ bits.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Sage Weil 2011-10-28 10:02:42 -07:00 committed by Christoph Hellwig
parent a78ef704a8
commit f0023bc617
3 changed files with 41 additions and 8 deletions
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1
Documentation/filesystems/Locking
View file

@ -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

40
fs/dcache.c
View file

@ -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)
{
@ -245,6 +245,9 @@ static void __dentry_lru_del(struct dentry *dentry)
dentry_stat.nr_unused--;
}
/*
* Remove a dentry with references from the LRU.
*/
static void dentry_lru_del(struct dentry *dentry)
{
if (!list_empty(&dentry->d_lru)) {
@ -254,6 +257,23 @@ static void dentry_lru_del(struct dentry *dentry)
}
}
/*
* Remove a dentry that is unreferenced and about to be pruned
* (unhashed and destroyed) from the LRU, and inform the file system.
* This wrapper should be called _prior_ to unhashing a victim dentry.
*/
static void dentry_lru_prune(struct dentry *dentry)
{
if (!list_empty(&dentry->d_lru)) {
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 +423,12 @@ 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.
* inform the fs via d_prune that this dentry is about to be
* unhashed and destroyed.
*/
dentry_lru_prune(dentry);
/* if it was on the hash then remove it */
__d_drop(dentry);
return d_kill(dentry, parent);
@ -854,8 +878,12 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
do {
struct inode *inode;
/* detach from the system */
dentry_lru_del(dentry);
/*
* remove the dentry from the lru, and inform
* the fs that this dentry is about to be
* unhashed and destroyed.
*/
dentry_lru_prune(dentry);
__d_shrink(dentry);
if (dentry->d_count != 0) {
@ -1283,6 +1311,8 @@ 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);

8
include/linux/dcache.h
View file

@ -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 *);
@ -184,8 +185,9 @@ struct dentry_operations {
#define DCACHE_OP_COMPARE 0x0002
#define DCACHE_OP_REVALIDATE 0x0004
#define DCACHE_OP_DELETE 0x0008
#define DCACHE_OP_PRUNE 0x0010
#define DCACHE_DISCONNECTED 0x0010
#define DCACHE_DISCONNECTED 0x0020
/* This dentry is possibly not currently connected to the dcache tree, in
* which case its parent will either be itself, or will have this flag as
* well. nfsd will not use a dentry with this bit set, but will first
@ -196,8 +198,8 @@ struct dentry_operations {
* dentry into place and return that dentry rather than the passed one,
* typically using d_splice_alias. */
#define DCACHE_REFERENCED 0x0020 /* Recently used, don't discard. */
#define DCACHE_RCUACCESS 0x0040 /* Entry has ever been RCU-visible */
#define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
#define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
#define DCACHE_CANT_MOUNT 0x0100
#define DCACHE_GENOCIDE 0x0200