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-rw-r--r--fs/dcache.c99
1 files changed, 78 insertions, 21 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index e989ecb44a65..509b49410943 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -356,7 +356,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
}
/*
- * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
+ * dentry_lru_(add|del|move_list) must be called with d_lock held.
*/
static void dentry_lru_add(struct dentry *dentry)
{
@@ -373,16 +373,26 @@ static void dentry_lru_add(struct dentry *dentry)
static void __dentry_lru_del(struct dentry *dentry)
{
list_del_init(&dentry->d_lru);
- dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
+ dentry->d_flags &= ~DCACHE_LRU_LIST;
dentry->d_sb->s_nr_dentry_unused--;
this_cpu_dec(nr_dentry_unused);
}
/*
* Remove a dentry with references from the LRU.
+ *
+ * If we are on the shrink list, then we can get to try_prune_one_dentry() and
+ * lose our last reference through the parent walk. In this case, we need to
+ * remove ourselves from the shrink list, not the LRU.
*/
static void dentry_lru_del(struct dentry *dentry)
{
+ if (dentry->d_flags & DCACHE_SHRINK_LIST) {
+ list_del_init(&dentry->d_lru);
+ dentry->d_flags &= ~DCACHE_SHRINK_LIST;
+ return;
+ }
+
if (!list_empty(&dentry->d_lru)) {
spin_lock(&dentry->d_sb->s_dentry_lru_lock);
__dentry_lru_del(dentry);
@@ -392,14 +402,16 @@ static void dentry_lru_del(struct dentry *dentry)
static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
{
+ BUG_ON(dentry->d_flags & DCACHE_SHRINK_LIST);
+
spin_lock(&dentry->d_sb->s_dentry_lru_lock);
if (list_empty(&dentry->d_lru)) {
dentry->d_flags |= DCACHE_LRU_LIST;
list_add_tail(&dentry->d_lru, list);
- dentry->d_sb->s_nr_dentry_unused++;
- this_cpu_inc(nr_dentry_unused);
} else {
list_move_tail(&dentry->d_lru, list);
+ dentry->d_sb->s_nr_dentry_unused--;
+ this_cpu_dec(nr_dentry_unused);
}
spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
}
@@ -497,7 +509,8 @@ EXPORT_SYMBOL(d_drop);
* If ref is non-zero, then decrement the refcount too.
* Returns dentry requiring refcount drop, or NULL if we're done.
*/
-static inline struct dentry *dentry_kill(struct dentry *dentry)
+static inline struct dentry *
+dentry_kill(struct dentry *dentry, int unlock_on_failure)
__releases(dentry->d_lock)
{
struct inode *inode;
@@ -506,8 +519,10 @@ static inline struct dentry *dentry_kill(struct dentry *dentry)
inode = dentry->d_inode;
if (inode && !spin_trylock(&inode->i_lock)) {
relock:
- spin_unlock(&dentry->d_lock);
- cpu_relax();
+ if (unlock_on_failure) {
+ spin_unlock(&dentry->d_lock);
+ cpu_relax();
+ }
return dentry; /* try again with same dentry */
}
if (IS_ROOT(dentry))
@@ -590,7 +605,7 @@ repeat:
return;
kill_it:
- dentry = dentry_kill(dentry);
+ dentry = dentry_kill(dentry, 1);
if (dentry)
goto repeat;
}
@@ -810,12 +825,12 @@ EXPORT_SYMBOL(d_prune_aliases);
*
* This may fail if locks cannot be acquired no problem, just try again.
*/
-static void try_prune_one_dentry(struct dentry *dentry)
+static struct dentry * try_prune_one_dentry(struct dentry *dentry)
__releases(dentry->d_lock)
{
struct dentry *parent;
- parent = dentry_kill(dentry);
+ parent = dentry_kill(dentry, 0);
/*
* If dentry_kill returns NULL, we have nothing more to do.
* if it returns the same dentry, trylocks failed. In either
@@ -827,17 +842,18 @@ static void try_prune_one_dentry(struct dentry *dentry)
* fragmentation.
*/
if (!parent)
- return;
+ return NULL;
if (parent == dentry)
- return;
+ return dentry;
/* Prune ancestors. */
dentry = parent;
while (dentry) {
if (lockref_put_or_lock(&dentry->d_lockref))
- return;
- dentry = dentry_kill(dentry);
+ return NULL;
+ dentry = dentry_kill(dentry, 1);
}
+ return NULL;
}
static void shrink_dentry_list(struct list_head *list)
@@ -856,21 +872,31 @@ static void shrink_dentry_list(struct list_head *list)
}
/*
+ * The dispose list is isolated and dentries are not accounted
+ * to the LRU here, so we can simply remove it from the list
+ * here regardless of whether it is referenced or not.
+ */
+ list_del_init(&dentry->d_lru);
+ dentry->d_flags &= ~DCACHE_SHRINK_LIST;
+
+ /*
* We found an inuse dentry which was not removed from
- * the LRU because of laziness during lookup. Do not free
- * it - just keep it off the LRU list.
+ * the LRU because of laziness during lookup. Do not free it.
*/
if (dentry->d_lockref.count) {
- dentry_lru_del(dentry);
spin_unlock(&dentry->d_lock);
continue;
}
-
rcu_read_unlock();
- try_prune_one_dentry(dentry);
+ dentry = try_prune_one_dentry(dentry);
rcu_read_lock();
+ if (dentry) {
+ dentry->d_flags |= DCACHE_SHRINK_LIST;
+ list_add(&dentry->d_lru, list);
+ spin_unlock(&dentry->d_lock);
+ }
}
rcu_read_unlock();
}
@@ -911,8 +937,10 @@ relock:
list_move(&dentry->d_lru, &referenced);
spin_unlock(&dentry->d_lock);
} else {
- list_move_tail(&dentry->d_lru, &tmp);
+ list_move(&dentry->d_lru, &tmp);
dentry->d_flags |= DCACHE_SHRINK_LIST;
+ this_cpu_dec(nr_dentry_unused);
+ sb->s_nr_dentry_unused--;
spin_unlock(&dentry->d_lock);
if (!--count)
break;
@@ -926,6 +954,27 @@ relock:
shrink_dentry_list(&tmp);
}
+/*
+ * Mark all the dentries as on being the dispose list so we don't think they are
+ * still on the LRU if we try to kill them from ascending the parent chain in
+ * try_prune_one_dentry() rather than directly from the dispose list.
+ */
+static void
+shrink_dcache_list(
+ struct list_head *dispose)
+{
+ struct dentry *dentry;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(dentry, dispose, d_lru) {
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_SHRINK_LIST;
+ spin_unlock(&dentry->d_lock);
+ }
+ rcu_read_unlock();
+ shrink_dentry_list(dispose);
+}
+
/**
* shrink_dcache_sb - shrink dcache for a superblock
* @sb: superblock
@@ -939,9 +988,17 @@ void shrink_dcache_sb(struct super_block *sb)
spin_lock(&sb->s_dentry_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
+ /*
+ * account for removal here so we don't need to handle it later
+ * even though the dentry is no longer on the lru list.
+ */
list_splice_init(&sb->s_dentry_lru, &tmp);
+ this_cpu_sub(nr_dentry_unused, sb->s_nr_dentry_unused);
+ sb->s_nr_dentry_unused = 0;
spin_unlock(&sb->s_dentry_lru_lock);
- shrink_dentry_list(&tmp);
+
+ shrink_dcache_list(&tmp);
+
spin_lock(&sb->s_dentry_lru_lock);
}
spin_unlock(&sb->s_dentry_lru_lock);
generated by cgit v1.2.3-55-g7522 (git 2.39.0) at 2024-06-17 04:06:34 +0200