From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH v3 3/4] limit nr_dentries per superblock Date: Sun, 14 Aug 2011 19:13:51 +0400 Message-ID: <1313334832-1150-4-git-send-email-glommer@parallels.com> References: <1313334832-1150-1-git-send-email-glommer@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Andrea Arcangeli , Rik van Riel , Nick Piggin , Eric Dumazet , Pavel Emelyanov , David Chinner , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Hugh Dickins , James Bottomley , Dave Hansen , Al Viro , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Return-path: In-Reply-To: <1313334832-1150-1-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org 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 CC: Dave Chinner CC: Eric Dumazet --- 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; -- 1.7.6