ceph: move sb->wb_pagevec_pool to be a global mempool

When doing some testing recently, I hit some page allocation failures
on mount, when creating the wb_pagevec_pool for the mount. That
requires 128k (32 contiguous pages), and after thrashing the memory
during an xfstests run, sometimes that would fail.

128k for each mount seems like a lot to hold in reserve for a rainy
day, so let's change this to a global mempool that gets allocated
when the module is plugged in.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/addr.c

@@ -862,8 +862,7 @@ static void writepages_finish(struct ceph_osd_request *req)
 
 	osd_data = osd_req_op_extent_osd_data(req, 0);
 	if (osd_data->pages_from_pool)
-		mempool_free(osd_data->pages,
-			     ceph_sb_to_client(inode->i_sb)->wb_pagevec_pool);
+		mempool_free(osd_data->pages, ceph_wb_pagevec_pool);
 	else
 		kfree(osd_data->pages);
 	ceph_osdc_put_request(req);
@@ -955,10 +954,10 @@ static int ceph_writepages_start(struct address_space *mapping,
 		int num_ops = 0, op_idx;
 		unsigned i, pvec_pages, max_pages, locked_pages = 0;
 		struct page **pages = NULL, **data_pages;
-		mempool_t *pool = NULL;	/* Becomes non-null if mempool used */
 		struct page *page;
 		pgoff_t strip_unit_end = 0;
 		u64 offset = 0, len = 0;
+		bool from_pool = false;
 
 		max_pages = wsize >> PAGE_SHIFT;
 
@@ -1057,16 +1056,16 @@ static int ceph_writepages_start(struct address_space *mapping,
 						      sizeof(*pages),
 						      GFP_NOFS);
 				if (!pages) {
-					pool = fsc->wb_pagevec_pool;
-					pages = mempool_alloc(pool, GFP_NOFS);
+					from_pool = true;
+					pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
 					BUG_ON(!pages);
 				}
 
 				len = 0;
 			} else if (page->index !=
 				   (offset + len) >> PAGE_SHIFT) {
-				if (num_ops >= (pool ?  CEPH_OSD_SLAB_OPS :
-							CEPH_OSD_MAX_OPS)) {
+				if (num_ops >= (from_pool ?  CEPH_OSD_SLAB_OPS :
+							     CEPH_OSD_MAX_OPS)) {
 					redirty_page_for_writepage(wbc, page);
 					unlock_page(page);
 					break;
@@ -1161,7 +1160,7 @@ static int ceph_writepages_start(struct address_space *mapping,
 				     offset, len);
 				osd_req_op_extent_osd_data_pages(req, op_idx,
 							data_pages, len, 0,
-							!!pool, false);
+							from_pool, false);
 				osd_req_op_extent_update(req, op_idx, len);
 
 				len = 0;
@@ -1188,12 +1187,12 @@ static int ceph_writepages_start(struct address_space *mapping,
 		dout("writepages got pages at %llu~%llu\n", offset, len);
 
 		osd_req_op_extent_osd_data_pages(req, op_idx, data_pages, len,
-						 0, !!pool, false);
+						 0, from_pool, false);
 		osd_req_op_extent_update(req, op_idx, len);
 
 		BUG_ON(op_idx + 1 != req->r_num_ops);
 
-		pool = NULL;
+		from_pool = false;
 		if (i < locked_pages) {
 			BUG_ON(num_ops <= req->r_num_ops);
 			num_ops -= req->r_num_ops;
@@ -1204,8 +1203,8 @@ static int ceph_writepages_start(struct address_space *mapping,
 			pages = kmalloc_array(locked_pages, sizeof(*pages),
 					      GFP_NOFS);
 			if (!pages) {
-				pool = fsc->wb_pagevec_pool;
-				pages = mempool_alloc(pool, GFP_NOFS);
+				from_pool = true;
+				pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
 				BUG_ON(!pages);
 			}
 			memcpy(pages, data_pages + i,

fs/ceph/super.c

@@ -637,8 +637,6 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
 					struct ceph_options *opt)
 {
 	struct ceph_fs_client *fsc;
-	int page_count;
-	size_t size;
 	int err;
 
 	fsc = kzalloc(sizeof(*fsc), GFP_KERNEL);
@@ -686,22 +684,12 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
 	if (!fsc->cap_wq)
 		goto fail_inode_wq;
 
-	/* set up mempools */
-	err = -ENOMEM;
-	page_count = fsc->mount_options->wsize >> PAGE_SHIFT;
-	size = sizeof (struct page *) * (page_count ? page_count : 1);
-	fsc->wb_pagevec_pool = mempool_create_kmalloc_pool(10, size);
-	if (!fsc->wb_pagevec_pool)
-		goto fail_cap_wq;
-
 	spin_lock(&ceph_fsc_lock);
 	list_add_tail(&fsc->metric_wakeup, &ceph_fsc_list);
 	spin_unlock(&ceph_fsc_lock);
 
 	return fsc;
 
-fail_cap_wq:
-	destroy_workqueue(fsc->cap_wq);
 fail_inode_wq:
 	destroy_workqueue(fsc->inode_wq);
 fail_client:
@@ -732,8 +720,6 @@ static void destroy_fs_client(struct ceph_fs_client *fsc)
 	destroy_workqueue(fsc->inode_wq);
 	destroy_workqueue(fsc->cap_wq);
 
-	mempool_destroy(fsc->wb_pagevec_pool);
-
 	destroy_mount_options(fsc->mount_options);
 
 	ceph_destroy_client(fsc->client);
@@ -752,6 +738,7 @@ struct kmem_cache *ceph_dentry_cachep;
 struct kmem_cache *ceph_file_cachep;
 struct kmem_cache *ceph_dir_file_cachep;
 struct kmem_cache *ceph_mds_request_cachep;
+mempool_t *ceph_wb_pagevec_pool;
 
 static void ceph_inode_init_once(void *foo)
 {
@@ -796,6 +783,10 @@ static int __init init_caches(void)
 	if (!ceph_mds_request_cachep)
 		goto bad_mds_req;
 
+	ceph_wb_pagevec_pool = mempool_create_kmalloc_pool(10, CEPH_MAX_WRITE_SIZE >> PAGE_SHIFT);
+	if (!ceph_wb_pagevec_pool)
+		goto bad_pagevec_pool;
+
 	error = ceph_fscache_register();
 	if (error)
 		goto bad_fscache;
@@ -804,6 +795,8 @@ static int __init init_caches(void)
 
 bad_fscache:
 	kmem_cache_destroy(ceph_mds_request_cachep);
+bad_pagevec_pool:
+	mempool_destroy(ceph_wb_pagevec_pool);
 bad_mds_req:
 	kmem_cache_destroy(ceph_dir_file_cachep);
 bad_dir_file:
@@ -834,6 +827,7 @@ static void destroy_caches(void)
 	kmem_cache_destroy(ceph_file_cachep);
 	kmem_cache_destroy(ceph_dir_file_cachep);
 	kmem_cache_destroy(ceph_mds_request_cachep);
+	mempool_destroy(ceph_wb_pagevec_pool);
 
 	ceph_fscache_unregister();
 }

fs/ceph/super.h

@@ -118,8 +118,6 @@ struct ceph_fs_client {
 
 	struct ceph_mds_client *mdsc;
 
-	/* writeback */
-	mempool_t *wb_pagevec_pool;
 	atomic_long_t writeback_count;
 
 	struct workqueue_struct *inode_wq;

include/linux/ceph/libceph.h

@@ -282,6 +282,7 @@ extern struct kmem_cache *ceph_dentry_cachep;
 extern struct kmem_cache *ceph_file_cachep;
 extern struct kmem_cache *ceph_dir_file_cachep;
 extern struct kmem_cache *ceph_mds_request_cachep;
+extern mempool_t *ceph_wb_pagevec_pool;
 
 /* ceph_common.c */
 extern bool libceph_compatible(void *data);