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: Sage Weil <sage@newdream.net> Signed-off-by: Christoph Hellwig <hch@lst.de>
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parent
a78ef704a8
commit
f0023bc617
3 changed files with 41 additions and 8 deletions
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@ -29,6 +29,7 @@ d_hash no no no maybe
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d_compare: yes no no maybe
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d_delete: no yes no no
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d_release: no no yes no
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d_prune: no yes no no
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d_iput: no no yes no
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d_dname: no no no no
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d_automount: no no yes no
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40
fs/dcache.c
40
fs/dcache.c
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@ -225,7 +225,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
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}
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/*
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* dentry_lru_(add|del|move_tail) must be called with d_lock held.
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* dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
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*/
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static void dentry_lru_add(struct dentry *dentry)
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{
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@ -245,6 +245,9 @@ static void __dentry_lru_del(struct dentry *dentry)
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dentry_stat.nr_unused--;
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}
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/*
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* Remove a dentry with references from the LRU.
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*/
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static void dentry_lru_del(struct dentry *dentry)
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{
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if (!list_empty(&dentry->d_lru)) {
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@ -254,6 +257,23 @@ static void dentry_lru_del(struct dentry *dentry)
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}
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}
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/*
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* Remove a dentry that is unreferenced and about to be pruned
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* (unhashed and destroyed) from the LRU, and inform the file system.
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* This wrapper should be called _prior_ to unhashing a victim dentry.
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*/
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static void dentry_lru_prune(struct dentry *dentry)
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{
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if (!list_empty(&dentry->d_lru)) {
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if (dentry->d_flags & DCACHE_OP_PRUNE)
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dentry->d_op->d_prune(dentry);
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spin_lock(&dcache_lru_lock);
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__dentry_lru_del(dentry);
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spin_unlock(&dcache_lru_lock);
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}
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}
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static void dentry_lru_move_tail(struct dentry *dentry)
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{
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spin_lock(&dcache_lru_lock);
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@ -403,8 +423,12 @@ relock:
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if (ref)
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dentry->d_count--;
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/* if dentry was on the d_lru list delete it from there */
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dentry_lru_del(dentry);
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/*
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* if dentry was on the d_lru list delete it from there.
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* inform the fs via d_prune that this dentry is about to be
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* unhashed and destroyed.
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*/
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dentry_lru_prune(dentry);
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/* if it was on the hash then remove it */
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__d_drop(dentry);
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return d_kill(dentry, parent);
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@ -854,8 +878,12 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
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do {
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struct inode *inode;
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/* detach from the system */
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dentry_lru_del(dentry);
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/*
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* remove the dentry from the lru, and inform
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* the fs that this dentry is about to be
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* unhashed and destroyed.
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*/
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dentry_lru_prune(dentry);
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__d_shrink(dentry);
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if (dentry->d_count != 0) {
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@ -1283,6 +1311,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
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dentry->d_flags |= DCACHE_OP_REVALIDATE;
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if (op->d_delete)
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dentry->d_flags |= DCACHE_OP_DELETE;
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if (op->d_prune)
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dentry->d_flags |= DCACHE_OP_PRUNE;
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}
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EXPORT_SYMBOL(d_set_d_op);
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@ -165,6 +165,7 @@ struct dentry_operations {
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unsigned int, const char *, const struct qstr *);
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int (*d_delete)(const struct dentry *);
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void (*d_release)(struct dentry *);
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void (*d_prune)(struct dentry *);
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void (*d_iput)(struct dentry *, struct inode *);
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char *(*d_dname)(struct dentry *, char *, int);
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struct vfsmount *(*d_automount)(struct path *);
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@ -184,8 +185,9 @@ struct dentry_operations {
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#define DCACHE_OP_COMPARE 0x0002
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#define DCACHE_OP_REVALIDATE 0x0004
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#define DCACHE_OP_DELETE 0x0008
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#define DCACHE_OP_PRUNE 0x0010
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#define DCACHE_DISCONNECTED 0x0010
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#define DCACHE_DISCONNECTED 0x0020
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/* This dentry is possibly not currently connected to the dcache tree, in
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* which case its parent will either be itself, or will have this flag as
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* well. nfsd will not use a dentry with this bit set, but will first
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@ -196,8 +198,8 @@ struct dentry_operations {
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* dentry into place and return that dentry rather than the passed one,
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* typically using d_splice_alias. */
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#define DCACHE_REFERENCED 0x0020 /* Recently used, don't discard. */
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#define DCACHE_RCUACCESS 0x0040 /* Entry has ever been RCU-visible */
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#define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
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#define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
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#define DCACHE_CANT_MOUNT 0x0100
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#define DCACHE_GENOCIDE 0x0200
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