This patch lays the foundation for us to limit the dcache size.
Each super block can have only a maximum amount of dentries under its
sub-tree. Allocation fails if we we're over limit and the cache
can't be pruned to free up space for the newcomers.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
CC: Dave Chinner <david@xxxxxxxxxxxxx>
---
fs/dcache.c | 25 +++++++++++++++++++++++++
fs/super.c | 1 +
include/linux/fs.h | 1 +
3 files changed, 27 insertions(+), 0 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index ac19d24..52a0faf 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1180,6 +1180,28 @@ void shrink_dcache_parent(struct dentry * parent)
}
EXPORT_SYMBOL(shrink_dcache_parent);
+static int dcache_mem_check(struct super_block *sb)
+{
+ int i;
+ int nr_dentry;
+ struct shrink_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ };
+
+ do {
+ nr_dentry = 0;
+ for_each_possible_cpu(i)
+ nr_dentry += per_cpu(*sb->s_nr_dentry, i);
+
+ if (nr_dentry < sb->s_nr_dentry_max)
+ return 0;
+
+ /* nr_pages = 1, lru_pages = 0 should get delta ~ 2 */
+ } while (shrink_one_shrinker(&sb->s_shrink, &sc, 1, 0));
+
+ return -ENOMEM;
+}
+
/**
* __d_alloc - allocate a dcache entry
* @sb: filesystem it will belong to
@@ -1195,6 +1217,9 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
struct dentry *dentry;
char *dname;
+ if (dcache_mem_check(sb))
+ return NULL;
+
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
if (!dentry)
return NULL;
diff --git a/fs/super.c b/fs/super.c
index 9345385..d9bcae8 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -130,6 +130,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
}
for_each_possible_cpu(i)
*per_cpu_ptr(s->s_nr_dentry, i) = 0;
+ s->s_nr_dentry_max = INT_MAX;
#ifdef CONFIG_SMP
s->s_files = alloc_percpu(struct list_head);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 35113fd..e90dcb4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1399,6 +1399,7 @@ struct super_block {
struct list_head s_dentry_lru; /* unused dentry lru */
int s_nr_dentry_unused; /* # of dentry on lru */
+ int s_nr_dentry_max; /* max # of dentry on this sb*/
int __percpu *s_nr_dentry; /* # of dentry on this sb */
/* s_inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
--
1.7.6
--
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