[PATCH v3 17/18] fuse,virtiofs: Maintain a list of busy elements

[Vivek Goyal <vgoyal@xxxxxxxxxx>]

This list will be used selecting fuse_dax_mapping to free when number of
free mappings drops below a threshold.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
 fs/fuse/file.c   | 22 ++++++++++++++++++++++
 fs/fuse/fuse_i.h |  7 +++++++
 fs/fuse/inode.c  |  4 ++++
 3 files changed, 33 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index aaa57c625af7..723602813ad6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -213,6 +213,23 @@ static struct fuse_dax_mapping *alloc_dax_mapping(struct fuse_conn *fc)
 	return dmap;
 }
 
+/* This assumes fc->lock is held */
+static void __dmap_remove_busy_list(struct fuse_conn *fc,
+				    struct fuse_dax_mapping *dmap)
+{
+	list_del_init(&dmap->busy_list);
+	WARN_ON(fc->nr_busy_ranges == 0);
+	fc->nr_busy_ranges--;
+}
+
+static void dmap_remove_busy_list(struct fuse_conn *fc,
+				  struct fuse_dax_mapping *dmap)
+{
+	spin_lock(&fc->lock);
+	__dmap_remove_busy_list(fc, dmap);
+	spin_unlock(&fc->lock);
+}
+
 /* This assumes fc->lock is held */
 static void __dmap_add_to_free_pool(struct fuse_conn *fc,
 				struct fuse_dax_mapping *dmap)
@@ -266,6 +283,10 @@ static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
 		/* Protected by fi->i_dmap_sem */
 		interval_tree_insert(&dmap->itn, &fi->dmap_tree);
 		fi->nr_dmaps++;
+		spin_lock(&fc->lock);
+		list_add_tail(&dmap->busy_list, &fc->busy_ranges);
+		fc->nr_busy_ranges++;
+		spin_unlock(&fc->lock);
 	}
 	return 0;
 }
@@ -335,6 +356,7 @@ static void dmap_reinit_add_to_free_pool(struct fuse_conn *fc,
 	pr_debug("fuse: freeing memory range start_idx=0x%lx end_idx=0x%lx "
 		 "window_offset=0x%llx length=0x%llx\n", dmap->itn.start,
 		 dmap->itn.last, dmap->window_offset, dmap->length);
+	__dmap_remove_busy_list(fc, dmap);
 	dmap->itn.start = dmap->itn.last = 0;
 	__dmap_add_to_free_pool(fc, dmap);
 }
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e555c9a33359..400a19a464ca 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -80,6 +80,9 @@ struct fuse_dax_mapping {
 	/* For interval tree in file/inode */
 	struct interval_tree_node itn;
 
+	/* Will connect in fc->busy_ranges to keep track busy memory */
+	struct list_head busy_list;
+
 	/** Position in DAX window */
 	u64 window_offset;
 
@@ -812,6 +815,10 @@ struct fuse_conn {
 	/** DAX device, non-NULL if DAX is supported */
 	struct dax_device *dax_dev;
 
+	/* List of memory ranges which are busy */
+	unsigned long nr_busy_ranges;
+	struct list_head busy_ranges;
+
 	/*
 	 * DAX Window Free Ranges
 	 */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 3735bc5fdfa2..671e84e3dd99 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -636,6 +636,8 @@ static void fuse_free_dax_mem_ranges(struct list_head *mem_list)
 	/* Free All allocated elements */
 	list_for_each_entry_safe(range, temp, mem_list, list) {
 		list_del(&range->list);
+		if (!list_empty(&range->busy_list))
+			list_del(&range->busy_list);
 		kfree(range);
 	}
 }
@@ -680,6 +682,7 @@ static int fuse_dax_mem_range_init(struct fuse_conn *fc,
 		 */
 		range->window_offset = i * FUSE_DAX_SZ;
 		range->length = FUSE_DAX_SZ;
+		INIT_LIST_HEAD(&range->busy_list);
 		list_add_tail(&range->list, &mem_ranges);
 	}
 
@@ -727,6 +730,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
 	fc->user_ns = get_user_ns(user_ns);
 	fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ;
 	INIT_LIST_HEAD(&fc->free_ranges);
+	INIT_LIST_HEAD(&fc->busy_ranges);
 }
 EXPORT_SYMBOL_GPL(fuse_conn_init);
 
-- 
2.25.4