return parent;
}
+/*
+ * Unhash a dentry without inserting an RCU walk barrier or checking that
+ * dentry->d_lock is locked. The caller must take care of that, if
+ * appropriate.
+ */
+static void __d_shrink(struct dentry *dentry)
+{
+ if (!d_unhashed(dentry)) {
+ struct hlist_bl_head *b;
+ if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
+ b = &dentry->d_sb->s_anon;
+ else
+ b = d_hash(dentry->d_parent, dentry->d_name.hash);
+
+ hlist_bl_lock(b);
+ __hlist_bl_del(&dentry->d_hash);
+ dentry->d_hash.pprev = NULL;
+ hlist_bl_unlock(b);
+ }
+}
+
/**
* d_drop - drop a dentry
* @dentry: dentry to drop
void __d_drop(struct dentry *dentry)
{
if (!d_unhashed(dentry)) {
- struct hlist_bl_head *b;
- if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
- b = &dentry->d_sb->s_anon;
- else
- b = d_hash(dentry->d_parent, dentry->d_name.hash);
-
- hlist_bl_lock(b);
- __hlist_bl_del(&dentry->d_hash);
- dentry->d_hash.pprev = NULL;
- hlist_bl_unlock(b);
-
+ __d_shrink(dentry);
dentry_rcuwalk_barrier(dentry);
}
}
}
EXPORT_SYMBOL(d_drop);
+/*
+ * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
+ * @dentry: dentry to drop
+ *
+ * This is called when we do a lookup on a placeholder dentry that needed to be
+ * looked up. The dentry should have been hashed in order for it to be found by
+ * the lookup code, but now needs to be unhashed while we do the actual lookup
+ * and clear the DCACHE_NEED_LOOKUP flag.
+ */
+void d_clear_need_lookup(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ __d_drop(dentry);
+ dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_clear_need_lookup);
+
/*
* Finish off a dentry we've decided to kill.
* dentry->d_lock must be held, returns with it unlocked.
if (d_unhashed(dentry))
goto kill_it;
- /* Otherwise leave it cached and ensure it's on the LRU */
- dentry->d_flags |= DCACHE_REFERENCED;
+ /*
+ * If this dentry needs lookup, don't set the referenced flag so that it
+ * is more likely to be cleaned up by the dcache shrinker in case of
+ * memory pressure.
+ */
+ if (!d_need_lookup(dentry))
+ dentry->d_flags |= DCACHE_REFERENCED;
dentry_lru_add(dentry);
dentry->d_count--;
*/
rcu_read_lock();
ret = dentry->d_parent;
- if (!ret) {
- rcu_read_unlock();
- goto out;
- }
spin_lock(&ret->d_lock);
if (unlikely(ret != dentry->d_parent)) {
spin_unlock(&ret->d_lock);
BUG_ON(!ret->d_count);
ret->d_count++;
spin_unlock(&ret->d_lock);
-out:
return ret;
}
EXPORT_SYMBOL(dget_parent);
*
* If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
*/
-static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
+static void __shrink_dcache_sb(struct super_block *sb, int count, int flags)
{
- /* called from prune_dcache() and shrink_dcache_parent() */
struct dentry *dentry;
LIST_HEAD(referenced);
LIST_HEAD(tmp);
- int cnt = *count;
relock:
spin_lock(&dcache_lru_lock);
} else {
list_move_tail(&dentry->d_lru, &tmp);
spin_unlock(&dentry->d_lock);
- if (!--cnt)
+ if (!--count)
break;
}
cond_resched_lock(&dcache_lru_lock);
spin_unlock(&dcache_lru_lock);
shrink_dentry_list(&tmp);
-
- *count = cnt;
}
/**
- * prune_dcache - shrink the dcache
- * @count: number of entries to try to free
+ * prune_dcache_sb - shrink the dcache
+ * @sb: superblock
+ * @nr_to_scan: number of entries to try to free
*
- * Shrink the dcache. This is done when we need more memory, or simply when we
- * need to unmount something (at which point we need to unuse all dentries).
+ * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
+ * done when we need more memory an called from the superblock shrinker
+ * function.
*
- * This function may fail to free any resources if all the dentries are in use.
+ * This function may fail to free any resources if all the dentries are in
+ * use.
*/
-static void prune_dcache(int count)
+void prune_dcache_sb(struct super_block *sb, int nr_to_scan)
{
- struct super_block *sb, *p = NULL;
- int w_count;
- int unused = dentry_stat.nr_unused;
- int prune_ratio;
- int pruned;
-
- if (unused == 0 || count == 0)
- return;
- if (count >= unused)
- prune_ratio = 1;
- else
- prune_ratio = unused / count;
- spin_lock(&sb_lock);
- list_for_each_entry(sb, &super_blocks, s_list) {
- if (list_empty(&sb->s_instances))
- continue;
- if (sb->s_nr_dentry_unused == 0)
- continue;
- sb->s_count++;
- /* Now, we reclaim unused dentrins with fairness.
- * We reclaim them same percentage from each superblock.
- * We calculate number of dentries to scan on this sb
- * as follows, but the implementation is arranged to avoid
- * overflows:
- * number of dentries to scan on this sb =
- * count * (number of dentries on this sb /
- * number of dentries in the machine)
- */
- spin_unlock(&sb_lock);
- if (prune_ratio != 1)
- w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
- else
- w_count = sb->s_nr_dentry_unused;
- pruned = w_count;
- /*
- * 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.
- */
- if (down_read_trylock(&sb->s_umount)) {
- if ((sb->s_root != NULL) &&
- (!list_empty(&sb->s_dentry_lru))) {
- __shrink_dcache_sb(sb, &w_count,
- DCACHE_REFERENCED);
- pruned -= w_count;
- }
- up_read(&sb->s_umount);
- }
- spin_lock(&sb_lock);
- if (p)
- __put_super(p);
- count -= pruned;
- p = sb;
- /* more work left to do? */
- if (count <= 0)
- break;
- }
- if (p)
- __put_super(p);
- spin_unlock(&sb_lock);
+ __shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED);
}
/**
static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
{
struct dentry *parent;
- unsigned detached = 0;
BUG_ON(!IS_ROOT(dentry));
- /* detach this root from the system */
- spin_lock(&dentry->d_lock);
- dentry_lru_del(dentry);
- __d_drop(dentry);
- spin_unlock(&dentry->d_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(&dentry->d_lock);
- list_for_each_entry(loop, &dentry->d_subdirs,
- d_u.d_child) {
- spin_lock_nested(&loop->d_lock,
- DENTRY_D_LOCK_NESTED);
- dentry_lru_del(loop);
- __d_drop(loop);
- spin_unlock(&loop->d_lock);
- }
- spin_unlock(&dentry->d_lock);
-
- /* move to the first child */
+ while (!list_empty(&dentry->d_subdirs))
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;
+ /* detach from the system */
+ dentry_lru_del(dentry);
+ __d_shrink(dentry);
+
if (dentry->d_count != 0) {
printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%s}"
list_del(&dentry->d_u.d_child);
} else {
parent = dentry->d_parent;
- spin_lock(&parent->d_lock);
parent->d_count--;
list_del(&dentry->d_u.d_child);
- spin_unlock(&parent->d_lock);
}
- detached++;
-
inode = dentry->d_inode;
if (inode) {
dentry->d_inode = NULL;
dentry = sb->s_root;
sb->s_root = NULL;
- spin_lock(&dentry->d_lock);
dentry->d_count--;
- spin_unlock(&dentry->d_lock);
shrink_dcache_for_umount_subtree(dentry);
while (!hlist_bl_empty(&sb->s_anon)) {
int found;
while ((found = select_parent(parent)) != 0)
- __shrink_dcache_sb(sb, &found, 0);
+ __shrink_dcache_sb(sb, found, 0);
}
EXPORT_SYMBOL(shrink_dcache_parent);
-/*
- * Scan `sc->nr_slab_to_reclaim' dentries and return the number which remain.
- *
- * We need to avoid reentering the filesystem if the caller is performing a
- * GFP_NOFS allocation attempt. One example deadlock is:
- *
- * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
- * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
- * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
- *
- * In this case we return -1 to tell the caller that we baled.
- */
-static int shrink_dcache_memory(struct shrinker *shrink,
- struct shrink_control *sc)
-{
- int nr = sc->nr_to_scan;
- gfp_t gfp_mask = sc->gfp_mask;
-
- if (nr) {
- if (!(gfp_mask & __GFP_FS))
- return -1;
- prune_dcache(nr);
- }
-
- return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
-}
-
-static struct shrinker dcache_shrinker = {
- .shrink = shrink_dcache_memory,
- .seeks = DEFAULT_SEEKS,
-};
-
/**
- * d_alloc - allocate a dcache entry
- * @parent: parent of entry to allocate
+ * __d_alloc - allocate a dcache entry
+ * @sb: filesystem it will belong to
* @name: qstr of the name
*
* Allocates a dentry. It returns %NULL if there is insufficient memory
* copied and the copy passed in may be reused after this call.
*/
-struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
+struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
{
struct dentry *dentry;
char *dname;
spin_lock_init(&dentry->d_lock);
seqcount_init(&dentry->d_seq);
dentry->d_inode = NULL;
- dentry->d_parent = NULL;
- dentry->d_sb = NULL;
+ dentry->d_parent = dentry;
+ dentry->d_sb = sb;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
INIT_HLIST_BL_NODE(&dentry->d_hash);
INIT_LIST_HEAD(&dentry->d_subdirs);
INIT_LIST_HEAD(&dentry->d_alias);
INIT_LIST_HEAD(&dentry->d_u.d_child);
-
- if (parent) {
- spin_lock(&parent->d_lock);
- /*
- * don't need child lock because it is not subject
- * to concurrency here
- */
- __dget_dlock(parent);
- dentry->d_parent = parent;
- dentry->d_sb = parent->d_sb;
- d_set_d_op(dentry, dentry->d_sb->s_d_op);
- list_add(&dentry->d_u.d_child, &parent->d_subdirs);
- spin_unlock(&parent->d_lock);
- }
+ d_set_d_op(dentry, dentry->d_sb->s_d_op);
this_cpu_inc(nr_dentry);
return dentry;
}
+
+/**
+ * d_alloc - allocate a dcache entry
+ * @parent: parent of entry to allocate
+ * @name: qstr of the name
+ *
+ * Allocates a dentry. It returns %NULL if there is insufficient memory
+ * available. On a success the dentry is returned. The name passed in is
+ * copied and the copy passed in may be reused after this call.
+ */
+struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
+{
+ struct dentry *dentry = __d_alloc(parent->d_sb, name);
+ if (!dentry)
+ return NULL;
+
+ spin_lock(&parent->d_lock);
+ /*
+ * don't need child lock because it is not subject
+ * to concurrency here
+ */
+ __dget_dlock(parent);
+ dentry->d_parent = parent;
+ list_add(&dentry->d_u.d_child, &parent->d_subdirs);
+ spin_unlock(&parent->d_lock);
+
+ return dentry;
+}
EXPORT_SYMBOL(d_alloc);
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
- struct dentry *dentry = d_alloc(NULL, name);
- if (dentry) {
- dentry->d_sb = sb;
- d_set_d_op(dentry, dentry->d_sb->s_d_op);
- dentry->d_parent = dentry;
+ struct dentry *dentry = __d_alloc(sb, name);
+ if (dentry)
dentry->d_flags |= DCACHE_DISCONNECTED;
- }
return dentry;
}
EXPORT_SYMBOL(d_alloc_pseudo);
if (root_inode) {
static const struct qstr name = { .name = "/", .len = 1 };
- res = d_alloc(NULL, &name);
- if (res) {
- res->d_sb = root_inode->i_sb;
- d_set_d_op(res, res->d_sb->s_d_op);
- res->d_parent = res;
+ res = __d_alloc(root_inode->i_sb, &name);
+ if (res)
d_instantiate(res, root_inode);
- }
}
return res;
}
if (res)
goto out_iput;
- tmp = d_alloc(NULL, &anonstring);
+ tmp = __d_alloc(inode->i_sb, &anonstring);
if (!tmp) {
res = ERR_PTR(-ENOMEM);
goto out_iput;
}
- tmp->d_parent = tmp; /* make sure dput doesn't croak */
-
spin_lock(&inode->i_lock);
res = __d_find_any_alias(inode);
/* attach a disconnected dentry */
spin_lock(&tmp->d_lock);
- tmp->d_sb = inode->i_sb;
- d_set_d_op(tmp, tmp->d_sb->s_d_op);
tmp->d_inode = inode;
tmp->d_flags |= DCACHE_DISCONNECTED;
list_add(&tmp->d_alias, &inode->i_dentry);
{
struct dentry *new = NULL;
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
if (inode && S_ISDIR(inode->i_mode)) {
spin_lock(&inode->i_lock);
new = __d_find_alias(inode, 1);
}
/*
- * Negative dentry: instantiate it unless the inode is a directory and
- * already has a dentry.
+ * We are going to instantiate this dentry, unhash it and clear the
+ * lookup flag so we can do that.
*/
- spin_lock(&inode->i_lock);
- if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
- __d_instantiate(found, inode);
- spin_unlock(&inode->i_lock);
- security_d_instantiate(found, inode);
- return found;
- }
+ if (unlikely(d_need_lookup(found)))
+ d_clear_need_lookup(found);
/*
- * In case a directory already has a (disconnected) entry grab a
- * reference to it, move it in place and use it.
+ * Negative dentry: instantiate it unless the inode is a directory and
+ * already has a dentry.
*/
- new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
- __dget(new);
- spin_unlock(&inode->i_lock);
- security_d_instantiate(found, inode);
- d_move(new, found);
- iput(inode);
- dput(found);
- return new;
+ new = d_splice_alias(inode, found);
+ if (new) {
+ dput(found);
+ found = new;
+ }
+ return found;
err_out:
iput(inode);
*/
if (read_seqcount_retry(&dentry->d_seq, *seq))
goto seqretry;
- if (parent->d_flags & DCACHE_OP_COMPARE) {
+ if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
if (parent->d_op->d_compare(parent, *inode,
dentry, i,
tlen, tname, name))
* @target: new dentry
*
* Update the dcache to reflect the move of a file name. Negative
- * dcache entries should not be moved in this way. Caller hold
- * rename_lock.
+ * dcache entries should not be moved in this way. Caller must hold
+ * rename_lock, the i_mutex of the source and target directories,
+ * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
*/
static void __d_move(struct dentry * dentry, struct dentry * target)
{
* @target: new dentry
*
* Update the dcache to reflect the move of a file name. Negative
- * dcache entries should not be moved in this way.
+ * dcache entries should not be moved in this way. See the locking
+ * requirements for __d_move.
*/
void d_move(struct dentry *dentry, struct dentry *target)
{
* @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
+ * root directory alias in its place if there is one. Caller must hold the
+ * i_mutex of the parent directory.
*/
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
*/
dentry_cache = KMEM_CACHE(dentry,
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
-
- register_shrinker(&dcache_shrinker);
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
git.openpandora.org / pandora-kernel.git / blobdiff