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Commit f0023bc6 authored by Sage Weil's avatar Sage Weil Committed by Christoph Hellwig
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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.

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

Signed-off-by: default avatarSage Weil <sage@newdream.net>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent a78ef704

Documentation/filesystems/Locking

+1 −0
Original line number Diff line number Diff line
@@ -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

fs/dcache.c

+35 −5
Original line number Diff line number Diff line
@@ -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 @@ static inline struct dentry *dentry_kill(struct dentry *dentry, int ref) 


	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);

include/linux/dcache.h

+5 −3
Original line number Diff line number Diff line
@@ -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