}
/*
- * Throw away a dentry - free the inode, dput the parent.
- * This requires that the LRU list has already been
- * removed.
+ * Throw away a dentry - free the inode, dput the parent. This requires that
+ * the LRU list has already been removed.
+ *
* Called with dcache_lock, drops it and then regains.
+ * Called with dentry->d_lock held, drops it.
*/
-static inline void prune_one_dentry(struct dentry * dentry)
+static void prune_one_dentry(struct dentry * dentry)
{
struct dentry * parent;
/**
* prune_dcache - shrink the dcache
* @count: number of entries to try and free
+ * @sb: if given, ignore dentries for other superblocks
+ * which are being unmounted.
*
* Shrink the dcache. This is done when we need
* more memory, or simply when we need to unmount
* all the dentries are in use.
*/
-static void prune_dcache(int count)
+static void prune_dcache(int count, struct super_block *sb)
{
spin_lock(&dcache_lock);
for (; count ; count--) {
struct dentry *dentry;
struct list_head *tmp;
+ struct rw_semaphore *s_umount;
cond_resched_lock(&dcache_lock);
tmp = dentry_unused.prev;
+ if (sb) {
+ /* Try to find a dentry for this sb, but don't try
+ * too hard, if they aren't near the tail they will
+ * be moved down again soon
+ */
+ int skip = count;
+ while (skip && tmp != &dentry_unused &&
+ list_entry(tmp, struct dentry, d_lru)->d_sb != sb) {
+ skip--;
+ tmp = tmp->prev;
+ }
+ }
if (tmp == &dentry_unused)
break;
list_del_init(tmp);
spin_unlock(&dentry->d_lock);
continue;
}
- prune_one_dentry(dentry);
+ /*
+ * If the dentry is not DCACHED_REFERENCED, it is time
+ * to remove it from the dcache, provided the super block is
+ * NULL (which means we are trying to reclaim memory)
+ * or this dentry belongs to the same super block that
+ * we want to shrink.
+ */
+ /*
+ * If this dentry is for "my" filesystem, then I can prune it
+ * without taking the s_umount lock (I already hold it).
+ */
+ if (sb && dentry->d_sb == sb) {
+ prune_one_dentry(dentry);
+ continue;
+ }
+ /*
+ * ...otherwise we need to be sure this filesystem isn't being
+ * unmounted, otherwise we could race with
+ * generic_shutdown_super(), and end up holding a reference to
+ * an inode while the filesystem is unmounted.
+ * So we try to get s_umount, and make sure s_root isn't NULL.
+ * (Take a local copy of s_umount to avoid a use-after-free of
+ * `dentry').
+ */
+ s_umount = &dentry->d_sb->s_umount;
+ if (down_read_trylock(s_umount)) {
+ if (dentry->d_sb->s_root != NULL) {
+ prune_one_dentry(dentry);
+ up_read(s_umount);
+ continue;
+ }
+ up_read(s_umount);
+ }
+ spin_unlock(&dentry->d_lock);
+ /* Cannot remove the first dentry, and it isn't appropriate
+ * to move it to the head of the list, so give up, and try
+ * later
+ */
+ break;
}
spin_unlock(&dcache_lock);
}
dentry = list_entry(tmp, struct dentry, d_lru);
if (dentry->d_sb != sb)
continue;
- list_del(tmp);
- list_add(tmp, &dentry_unused);
+ list_move(tmp, &dentry_unused);
}
/*
* of the unused list for prune_dcache
*/
if (!atomic_read(&dentry->d_count)) {
- list_add(&dentry->d_lru, dentry_unused.prev);
+ list_add_tail(&dentry->d_lru, &dentry_unused);
dentry_stat.nr_unused++;
found++;
}
int found;
while ((found = select_parent(parent)) != 0)
- prune_dcache(found);
-}
-
-/**
- * shrink_dcache_anon - further prune the cache
- * @head: head of d_hash list of dentries to prune
- *
- * Prune the dentries that are anonymous
- *
- * parsing d_hash list does not hlist_for_each_entry_rcu() as it
- * done under dcache_lock.
- *
- */
-void shrink_dcache_anon(struct hlist_head *head)
-{
- struct hlist_node *lp;
- int found;
- do {
- found = 0;
- spin_lock(&dcache_lock);
- hlist_for_each(lp, head) {
- struct dentry *this = hlist_entry(lp, struct dentry, d_hash);
- if (!list_empty(&this->d_lru)) {
- dentry_stat.nr_unused--;
- list_del_init(&this->d_lru);
- }
-
- /*
- * move only zero ref count dentries to the end
- * of the unused list for prune_dcache
- */
- if (!atomic_read(&this->d_count)) {
- list_add_tail(&this->d_lru, &dentry_unused);
- dentry_stat.nr_unused++;
- found++;
- }
- }
- spin_unlock(&dcache_lock);
- prune_dcache(found);
- } while(found);
+ prune_dcache(found, parent->d_sb);
}
/*
if (nr) {
if (!(gfp_mask & __GFP_FS))
return -1;
- prune_dcache(nr);
+ prune_dcache(nr, NULL);
}
return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}
return found;
}
+/**
+ * d_hash_and_lookup - hash the qstr then search for a dentry
+ * @dir: Directory to search in
+ * @name: qstr of name we wish to find
+ *
+ * On hash failure or on lookup failure NULL is returned.
+ */
+struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
+{
+ struct dentry *dentry = NULL;
+
+ /*
+ * Check for a fs-specific hash function. Note that we must
+ * calculate the standard hash first, as the d_op->d_hash()
+ * routine may choose to leave the hash value unchanged.
+ */
+ name->hash = full_name_hash(name->name, name->len);
+ if (dir->d_op && dir->d_op->d_hash) {
+ if (dir->d_op->d_hash(dir, name) < 0)
+ goto out;
+ }
+ dentry = d_lookup(dir, name);
+out:
+ return dentry;
+}
+
/**
* d_validate - verify dentry provided from insecure source
* @dentry: The dentry alleged to be valid child of @dparent
struct dentry * dentry;
ino_t ino = 0;
- /*
- * Check for a fs-specific hash function. Note that we must
- * calculate the standard hash first, as the d_op->d_hash()
- * routine may choose to leave the hash value unchanged.
- */
- name->hash = full_name_hash(name->name, name->len);
- if (dir->d_op && dir->d_op->d_hash)
- {
- if (dir->d_op->d_hash(dir, name) != 0)
- goto out;
- }
-
- dentry = d_lookup(dir, name);
- if (dentry)
- {
+ dentry = d_hash_and_lookup(dir, name);
+ if (dentry) {
if (dentry->d_inode)
ino = dentry->d_inode->i_ino;
dput(dentry);
}
-out:
return ino;
}
git.samba.org / sfrench / cifs-2.6.git / blobdiff