On Sun, Aug 14, 2011 at 6:13 PM, Glauber Costa <glommer@xxxxxxxxxxxxx> wrote:
> 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>
> CC: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> ---
> fs/dcache.c | 28 ++++++++++++++++++++++++++++
> fs/super.c | 1 +
> include/linux/fs.h | 1 +
> 3 files changed, 30 insertions(+), 0 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 815d9fd..ddd02a2 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1180,6 +1180,31 @@ void shrink_dcache_parent(struct dentry * parent)
> }
> EXPORT_SYMBOL(shrink_dcache_parent);
>
> +static inline int dcache_mem_check(struct super_block *sb)
> +{
> + struct shrink_control sc = {
> + .gfp_mask = GFP_KERNEL,
> + };
> +
> + if (sb->s_nr_dentry_max == INT_MAX)
> + return 0;
> +
> + do {
> + int nr_dentry;
> +
> + nr_dentry = percpu_counter_read_positive(&sb->s_nr_dentry);
> + if (nr_dentry > sb->s_nr_dentry_max)
> + nr_dentry =
> + percpu_counter_sum_positive(&sb->s_nr_dentry);
> + 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 +1220,9 @@ 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 e95ac4f..3db40fb 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -121,6 +121,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
> }
>
> percpu_counter_init(&s->s_nr_dentry, 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 8150f52..bc773c3 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1400,6 +1400,7 @@ struct super_block {
> int s_nr_dentry_unused; /* # of dentry on lru */
>
> struct percpu_counter s_nr_dentry; /* # of dentry on this sb */
> + int s_nr_dentry_max; /* max # of dentry on this sb*/
>
> /* s_inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
> spinlock_t s_inode_lru_lock ____cacheline_aligned_in_smp;
We track the total number of objects in mm/slub.c when
CONFIG_SLUB_DEBUG is enabled (look for n->total_objects in the code).
Have you considered extending that for this purpose?
Pekka
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
