[PATCH v2 11/22] netfs: Use mempools for allocating requests and subrequests

David Howells
2024-04-30T14:01:56Z

Use mempools for allocating requests and subrequests in an effort to make
sure that allocation always succeeds so that when performing writeback we
can always make progress.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
fs/netfs/internal.h | 2 ++
fs/netfs/main.c | 51 ++++++++++++++++++++++++++++++++-----
fs/netfs/objects.c | 59 ++++++++++++++++++++++++++++---------------
include/linux/netfs.h | 5 ++--
4 files changed, 89 insertions(+), 28 deletions(-)

diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index 156ab138e224..c67da478cd2b 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -37,6 +37,8 @@ int netfs_begin_read(struct netfs_io_request *rreq, bool sync);
extern unsigned int netfs_debug;
extern struct list_head netfs_io_requests;
extern spinlock_t netfs_proc_lock;
+extern mempool_t netfs_request_pool;
+extern mempool_t netfs_subrequest_pool;

#ifdef CONFIG_PROC_FS
static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq)
diff --git a/fs/netfs/main.c b/fs/netfs/main.c
index 844efbb2e7a2..4805b9377364 100644
--- a/fs/netfs/main.c
+++ b/fs/netfs/main.c
@@ -7,6 +7,7 @@

#include <linux/module.h>
#include <linux/export.h>
+#include <linux/mempool.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include "internal.h"
@@ -23,6 +24,11 @@ unsigned netfs_debug;
module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");

+static struct kmem_cache *netfs_request_slab;
+static struct kmem_cache *netfs_subrequest_slab;
+mempool_t netfs_request_pool;
+mempool_t netfs_subrequest_pool;
+
#ifdef CONFIG_PROC_FS
LIST_HEAD(netfs_io_requests);
DEFINE_SPINLOCK(netfs_proc_lock);
@@ -98,25 +104,54 @@ static int __init netfs_init(void)
{
int ret = -ENOMEM;

+ netfs_request_slab = kmem_cache_create("netfs_request",
+ sizeof(struct netfs_io_request), 0,
+ SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT,
+ NULL);
+ if (!netfs_request_slab)
+ goto error_req;
+
+ if (mempool_init_slab_pool(&netfs_request_pool, 100, netfs_request_slab) < 0)
+ goto error_reqpool;
+
+ netfs_subrequest_slab = kmem_cache_create("netfs_subrequest",
+ sizeof(struct netfs_io_subrequest), 0,
+ SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT,
+ NULL);
+ if (!netfs_subrequest_slab)
+ goto error_subreq;
+
+ if (mempool_init_slab_pool(&netfs_subrequest_pool, 100, netfs_subrequest_slab) < 0)
+ goto error_subreqpool;
+
if (!proc_mkdir("fs/netfs", NULL))
- goto error;
+ goto error_proc;
if (!proc_create_seq("fs/netfs/requests", S_IFREG | 0444, NULL,
&netfs_requests_seq_ops))
- goto error_proc;
+ goto error_procfile;
#ifdef CONFIG_FSCACHE_STATS
if (!proc_create_single("fs/netfs/stats", S_IFREG | 0444, NULL,
netfs_stats_show))
- goto error_proc;
+ goto error_procfile;
#endif

ret = fscache_init();
if (ret < 0)
- goto error_proc;
+ goto error_fscache;
return 0;

-error_proc:
+error_fscache:
+error_procfile:
remove_proc_entry("fs/netfs", NULL);
-error:
+error_proc:
+ mempool_exit(&netfs_subrequest_pool);
+error_subreqpool:
+ kmem_cache_destroy(netfs_subrequest_slab);
+error_subreq:
+ mempool_exit(&netfs_request_pool);
+error_reqpool:
+ kmem_cache_destroy(netfs_request_slab);
+error_req:
return ret;
}
fs_initcall(netfs_init);
@@ -125,5 +160,9 @@ static void __exit netfs_exit(void)
{
fscache_exit();
remove_proc_entry("fs/netfs", NULL);
+ mempool_exit(&netfs_subrequest_pool);
+ kmem_cache_destroy(netfs_subrequest_slab);
+ mempool_exit(&netfs_request_pool);
+ kmem_cache_destroy(netfs_request_slab);
}
module_exit(netfs_exit);
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index 8acc03a64059..1a4e2ce735ce 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -6,6 +6,8 @@
*/

#include <linux/slab.h>
+#include <linux/mempool.h>
+#include <linux/delay.h>
#include "internal.h"

/*
@@ -20,17 +22,22 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
struct inode *inode = file ? file_inode(file) : mapping->host;
struct netfs_inode *ctx = netfs_inode(inode);
struct netfs_io_request *rreq;
+ mempool_t *mempool = ctx->ops->request_pool ?: &netfs_request_pool;
+ struct kmem_cache *cache = mempool->pool_data;
bool is_unbuffered = (origin == NETFS_UNBUFFERED_WRITE ||
origin == NETFS_DIO_READ ||
origin == NETFS_DIO_WRITE);
bool cached = !is_unbuffered && netfs_is_cache_enabled(ctx);
int ret;

- rreq = kzalloc(ctx->ops->io_request_size ?: sizeof(struct netfs_io_request),
- GFP_KERNEL);
- if (!rreq)
- return ERR_PTR(-ENOMEM);
+ for (;;) {
+ rreq = mempool_alloc(mempool, GFP_KERNEL);
+ if (rreq)
+ break;
+ msleep(10);
+ }

+ memset(rreq, 0, kmem_cache_size(cache));
rreq->start = start;
rreq->len = len;
rreq->upper_len = len;
@@ -56,7 +63,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
if (rreq->netfs_ops->init_request) {
ret = rreq->netfs_ops->init_request(rreq, file);
if (ret < 0) {
- kfree(rreq);
+ mempool_free(rreq, rreq->netfs_ops->request_pool ?: &netfs_request_pool);
return ERR_PTR(ret);
}
}
@@ -88,6 +95,14 @@ void netfs_clear_subrequests(struct netfs_io_request *rreq, bool was_async)
}
}

+static void netfs_free_request_rcu(struct rcu_head *rcu)
+{
+ struct netfs_io_request *rreq = container_of(rcu, struct netfs_io_request, rcu);
+
+ mempool_free(rreq, rreq->netfs_ops->request_pool ?: &netfs_request_pool);
+ netfs_stat_d(&netfs_n_rh_rreq);
+}
+
static void netfs_free_request(struct work_struct *work)
{
struct netfs_io_request *rreq =
@@ -110,8 +125,7 @@ static void netfs_free_request(struct work_struct *work)
}
kvfree(rreq->direct_bv);
}
- kfree_rcu(rreq, rcu);
- netfs_stat_d(&netfs_n_rh_rreq);
+ call_rcu(&rreq->rcu, netfs_free_request_rcu);
}

void netfs_put_request(struct netfs_io_request *rreq, bool was_async,
@@ -143,20 +157,25 @@ void netfs_put_request(struct netfs_io_request *rreq, bool was_async,
struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq)
{
struct netfs_io_subrequest *subreq;
-
- subreq = kzalloc(rreq->netfs_ops->io_subrequest_size ?:
- sizeof(struct netfs_io_subrequest),
- GFP_KERNEL);
- if (subreq) {
- INIT_WORK(&subreq->work, NULL);
- INIT_LIST_HEAD(&subreq->rreq_link);
- refcount_set(&subreq->ref, 2);
- subreq->rreq = rreq;
- subreq->debug_index = atomic_inc_return(&rreq->subreq_counter);
- netfs_get_request(rreq, netfs_rreq_trace_get_subreq);
- netfs_stat(&netfs_n_rh_sreq);
+ mempool_t *mempool = rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool;
+ struct kmem_cache *cache = mempool->pool_data;
+
+ for (;;) {
+ subreq = mempool_alloc(rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool,
+ GFP_KERNEL);
+ if (subreq)
+ break;
+ msleep(10);
}

+ memset(subreq, 0, kmem_cache_size(cache));
+ INIT_WORK(&subreq->work, NULL);
+ INIT_LIST_HEAD(&subreq->rreq_link);
+ refcount_set(&subreq->ref, 2);
+ subreq->rreq = rreq;
+ subreq->debug_index = atomic_inc_return(&rreq->subreq_counter);
+ netfs_get_request(rreq, netfs_rreq_trace_get_subreq);
+ netfs_stat(&netfs_n_rh_sreq);
return subreq;
}

@@ -178,7 +197,7 @@ static void netfs_free_subrequest(struct netfs_io_subrequest *subreq,
trace_netfs_sreq(subreq, netfs_sreq_trace_free);
if (rreq->netfs_ops->free_subrequest)
rreq->netfs_ops->free_subrequest(subreq);
- kfree(subreq);
+ mempool_free(subreq, rreq->netfs_ops->subrequest_pool ?: &netfs_subrequest_pool);
netfs_stat_d(&netfs_n_rh_sreq);
netfs_put_request(rreq, was_async, netfs_rreq_trace_put_subreq);
}
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 3af589dabd7f..0b6c2c2d3c23 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -20,6 +20,7 @@
#include <linux/uio.h>

enum netfs_sreq_ref_trace;
+typedef struct mempool_s mempool_t;

/**
* folio_start_private_2 - Start an fscache write on a folio. [DEPRECATED]
@@ -236,8 +237,8 @@ struct netfs_io_request {
* Operations the network filesystem can/must provide to the helpers.
*/
struct netfs_request_ops {
- unsigned int io_request_size; /* Alloc size for netfs_io_request struct */
- unsigned int io_subrequest_size; /* Alloc size for netfs_io_subrequest struct */
+ mempool_t *request_pool;
+ mempool_t *subrequest_pool;
int (*init_request)(struct netfs_io_request *rreq, struct file *file);
void (*free_request)(struct netfs_io_request *rreq);
void (*free_subrequest)(struct netfs_io_subrequest *rreq);