* the dcache entry is deleted or garbage collected.
*/
+#include <linux/config.h>
#include <linux/syscalls.h>
#include <linux/string.h>
#include <linux/mm.h>
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
-static __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
+static seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
EXPORT_SYMBOL(dcache_lock);
}
/*
- * 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 void prune_one_dentry(struct dentry * dentry)
+static inline 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, struct super_block *sb)
+static void prune_dcache(int count)
{
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;
}
- /*
- * 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;
+ prune_one_dentry(dentry);
}
spin_unlock(&dcache_lock);
}
dentry = list_entry(tmp, struct dentry, d_lru);
if (dentry->d_sb != sb)
continue;
- list_move(tmp, &dentry_unused);
+ list_del(tmp);
+ list_add(tmp, &dentry_unused);
}
/*
spin_unlock(&dcache_lock);
}
-/*
- * destroy a single subtree of dentries for unmount
- * - see the comments on shrink_dcache_for_umount() for a description of the
- * locking
- */
-static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
-{
- struct dentry *parent;
-
- BUG_ON(!IS_ROOT(dentry));
-
- /* detach this root from the system */
- spin_lock(&dcache_lock);
- if (!list_empty(&dentry->d_lru)) {
- dentry_stat.nr_unused--;
- list_del_init(&dentry->d_lru);
- }
- __d_drop(dentry);
- spin_unlock(&dcache_lock);
-
- for (;;) {
- /* descend to the first leaf in the current subtree */
- while (!list_empty(&dentry->d_subdirs)) {
- struct dentry *loop;
-
- /* this is a branch with children - detach all of them
- * from the system in one go */
- spin_lock(&dcache_lock);
- list_for_each_entry(loop, &dentry->d_subdirs,
- d_u.d_child) {
- if (!list_empty(&loop->d_lru)) {
- dentry_stat.nr_unused--;
- list_del_init(&loop->d_lru);
- }
-
- __d_drop(loop);
- cond_resched_lock(&dcache_lock);
- }
- spin_unlock(&dcache_lock);
-
- /* move to the first child */
- dentry = list_entry(dentry->d_subdirs.next,
- struct dentry, d_u.d_child);
- }
-
- /* consume the dentries from this leaf up through its parents
- * until we find one with children or run out altogether */
- do {
- struct inode *inode;
-
- if (atomic_read(&dentry->d_count) != 0) {
- printk(KERN_ERR
- "BUG: Dentry %p{i=%lx,n=%s}"
- " still in use (%d)"
- " [unmount of %s %s]\n",
- dentry,
- dentry->d_inode ?
- dentry->d_inode->i_ino : 0UL,
- dentry->d_name.name,
- atomic_read(&dentry->d_count),
- dentry->d_sb->s_type->name,
- dentry->d_sb->s_id);
- BUG();
- }
-
- parent = dentry->d_parent;
- if (parent == dentry)
- parent = NULL;
- else
- atomic_dec(&parent->d_count);
-
- list_del(&dentry->d_u.d_child);
- dentry_stat.nr_dentry--; /* For d_free, below */
-
- inode = dentry->d_inode;
- if (inode) {
- dentry->d_inode = NULL;
- list_del_init(&dentry->d_alias);
- if (dentry->d_op && dentry->d_op->d_iput)
- dentry->d_op->d_iput(dentry, inode);
- else
- iput(inode);
- }
-
- d_free(dentry);
-
- /* finished when we fall off the top of the tree,
- * otherwise we ascend to the parent and move to the
- * next sibling if there is one */
- if (!parent)
- return;
-
- dentry = parent;
-
- } while (list_empty(&dentry->d_subdirs));
-
- dentry = list_entry(dentry->d_subdirs.next,
- struct dentry, d_u.d_child);
- }
-}
-
-/*
- * destroy the dentries attached to a superblock on unmounting
- * - we don't need to use dentry->d_lock, and only need dcache_lock when
- * removing the dentry from the system lists and hashes because:
- * - the superblock is detached from all mountings and open files, so the
- * dentry trees will not be rearranged by the VFS
- * - s_umount is write-locked, so the memory pressure shrinker will ignore
- * any dentries belonging to this superblock that it comes across
- * - the filesystem itself is no longer permitted to rearrange the dentries
- * in this superblock
- */
-void shrink_dcache_for_umount(struct super_block *sb)
-{
- struct dentry *dentry;
-
- if (down_read_trylock(&sb->s_umount))
- BUG();
-
- dentry = sb->s_root;
- sb->s_root = NULL;
- atomic_dec(&dentry->d_count);
- shrink_dcache_for_umount_subtree(dentry);
-
- while (!hlist_empty(&sb->s_anon)) {
- dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
- shrink_dcache_for_umount_subtree(dentry);
- }
-}
-
/*
* Search for at least 1 mount point in the dentry's subdirs.
* We descend to the next level whenever the d_subdirs
* of the unused list for prune_dcache
*/
if (!atomic_read(&dentry->d_count)) {
- list_add_tail(&dentry->d_lru, &dentry_unused);
+ list_add(&dentry->d_lru, dentry_unused.prev);
dentry_stat.nr_unused++;
found++;
}
int found;
while ((found = select_parent(parent)) != 0)
- prune_dcache(found, parent->d_sb);
+ 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);
}
/*
if (nr) {
if (!(gfp_mask & __GFP_FS))
return -1;
- prune_dcache(nr, NULL);
+ prune_dcache(nr);
}
return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}
* (or otherwise set) by the caller to indicate that it is now
* in use by the dcache.
*/
-static struct dentry *__d_instantiate_unique(struct dentry *entry,
- struct inode *inode)
+struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
{
struct dentry *alias;
int len = entry->d_name.len;
const char *name = entry->d_name.name;
unsigned int hash = entry->d_name.hash;
- if (!inode) {
- entry->d_inode = NULL;
- return NULL;
- }
-
+ BUG_ON(!list_empty(&entry->d_alias));
+ spin_lock(&dcache_lock);
+ if (!inode)
+ goto do_negative;
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct qstr *qstr = &alias->d_name;
if (memcmp(qstr->name, name, len))
continue;
dget_locked(alias);
+ spin_unlock(&dcache_lock);
+ BUG_ON(!d_unhashed(alias));
+ iput(inode);
return alias;
}
-
list_add(&entry->d_alias, &inode->i_dentry);
+do_negative:
entry->d_inode = inode;
fsnotify_d_instantiate(entry, inode);
- return NULL;
-}
-
-struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
-{
- struct dentry *result;
-
- BUG_ON(!list_empty(&entry->d_alias));
-
- spin_lock(&dcache_lock);
- result = __d_instantiate_unique(entry, inode);
spin_unlock(&dcache_lock);
-
- if (!result) {
- security_d_instantiate(entry, inode);
- return NULL;
- }
-
- BUG_ON(!d_unhashed(result));
- iput(inode);
- return result;
+ security_d_instantiate(entry, inode);
+ return NULL;
}
-
EXPORT_SYMBOL(d_instantiate_unique);
/**
hlist_add_head_rcu(&entry->d_hash, list);
}
-static void _d_rehash(struct dentry * entry)
-{
- __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
-}
-
/**
* d_rehash - add an entry back to the hash
* @entry: dentry to add to the hash
void d_rehash(struct dentry * entry)
{
+ struct hlist_head *list = d_hash(entry->d_parent, entry->d_name.hash);
+
spin_lock(&dcache_lock);
spin_lock(&entry->d_lock);
- _d_rehash(entry);
+ __d_rehash(entry, list);
spin_unlock(&entry->d_lock);
spin_unlock(&dcache_lock);
}
*/
if (target < dentry) {
spin_lock(&target->d_lock);
- spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ spin_lock(&dentry->d_lock);
} else {
spin_lock(&dentry->d_lock);
- spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
+ spin_lock(&target->d_lock);
}
/* Move the dentry to the target hash queue, if on different bucket */
kfree(target->d_extra_attributes);
target->d_extra_attributes = NULL;
}
-
+
list_del(&dentry->d_u.d_child);
list_del(&target->d_u.d_child);
spin_unlock(&dcache_lock);
}
-/*
- * Prepare an anonymous dentry for life in the superblock's dentry tree as a
- * named dentry in place of the dentry to be replaced.
- */
-static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
-{
- struct dentry *dparent, *aparent;
-
- switch_names(dentry, anon);
- do_switch(dentry->d_name.len, anon->d_name.len);
- do_switch(dentry->d_name.hash, anon->d_name.hash);
-
- dparent = dentry->d_parent;
- aparent = anon->d_parent;
-
- dentry->d_parent = (aparent == anon) ? dentry : aparent;
- list_del(&dentry->d_u.d_child);
- if (!IS_ROOT(dentry))
- list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
- else
- INIT_LIST_HEAD(&dentry->d_u.d_child);
-
- anon->d_parent = (dparent == dentry) ? anon : dparent;
- list_del(&anon->d_u.d_child);
- if (!IS_ROOT(anon))
- list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
- else
- INIT_LIST_HEAD(&anon->d_u.d_child);
-
- anon->d_flags &= ~DCACHE_DISCONNECTED;
-}
-
-/**
- * d_materialise_unique - introduce an inode into the tree
- * @dentry: candidate dentry
- * @inode: inode to bind to the dentry, to which aliases may be attached
- *
- * Introduces an dentry into the tree, substituting an extant disconnected
- * root directory alias in its place if there is one
- */
-struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
-{
- struct dentry *alias, *actual;
-
- BUG_ON(!d_unhashed(dentry));
-
- spin_lock(&dcache_lock);
-
- if (!inode) {
- actual = dentry;
- dentry->d_inode = NULL;
- goto found_lock;
- }
-
- /* See if a disconnected directory already exists as an anonymous root
- * that we should splice into the tree instead */
- if (S_ISDIR(inode->i_mode) && (alias = __d_find_alias(inode, 1))) {
- spin_lock(&alias->d_lock);
-
- /* Is this a mountpoint that we could splice into our tree? */
- if (IS_ROOT(alias))
- goto connect_mountpoint;
-
- if (alias->d_name.len == dentry->d_name.len &&
- alias->d_parent == dentry->d_parent &&
- memcmp(alias->d_name.name,
- dentry->d_name.name,
- dentry->d_name.len) == 0)
- goto replace_with_alias;
-
- spin_unlock(&alias->d_lock);
-
- /* Doh! Seem to be aliasing directories for some reason... */
- dput(alias);
- }
-
- /* Add a unique reference */
- actual = __d_instantiate_unique(dentry, inode);
- if (!actual)
- actual = dentry;
- else if (unlikely(!d_unhashed(actual)))
- goto shouldnt_be_hashed;
-
-found_lock:
- spin_lock(&actual->d_lock);
-found:
- _d_rehash(actual);
- spin_unlock(&actual->d_lock);
- spin_unlock(&dcache_lock);
-
- if (actual == dentry) {
- security_d_instantiate(dentry, inode);
- return NULL;
- }
-
- iput(inode);
- return actual;
-
- /* Convert the anonymous/root alias into an ordinary dentry */
-connect_mountpoint:
- __d_materialise_dentry(dentry, alias);
-
- /* Replace the candidate dentry with the alias in the tree */
-replace_with_alias:
- __d_drop(alias);
- actual = alias;
- goto found;
-
-shouldnt_be_hashed:
- spin_unlock(&dcache_lock);
- BUG();
- goto shouldnt_be_hashed;
-}
-
/**
* d_path - return the path of a dentry
* @dentry: dentry to report
EXPORT_SYMBOL(d_invalidate);
EXPORT_SYMBOL(d_lookup);
EXPORT_SYMBOL(d_move);
-EXPORT_SYMBOL_GPL(d_materialise_unique);
EXPORT_SYMBOL(d_path);
EXPORT_SYMBOL(d_prune_aliases);
EXPORT_SYMBOL(d_rehash);
git://git.onelab.eu / linux-2.6.git / blobdiff