[PATCH v4 06/39] netfs: Add a procfile to list in-progress requests

David Howells
2023-12-13T15:24:25Z

Add a procfile, /proc/fs/netfs/requests, to list in-progress netfslib I/O
requests.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
fs/netfs/internal.h | 22 ++++++++++++++
fs/netfs/main.c | 69 ++++++++++++++++++++++++++++++++++++++++++-
fs/netfs/objects.c | 4 ++-
include/linux/netfs.h | 6 +++-
4 files changed, 98 insertions(+), 3 deletions(-)

diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index a15fe67e1db7..937d9a22f178 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -33,6 +33,28 @@ int netfs_begin_read(struct netfs_io_request *rreq, bool sync);
* main.c
*/
extern unsigned int netfs_debug;
+extern struct list_head netfs_io_requests;
+extern spinlock_t netfs_proc_lock;
+
+#ifdef CONFIG_PROC_FS
+static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq)
+{
+ spin_lock(&netfs_proc_lock);
+ list_add_tail_rcu(&rreq->proc_link, &netfs_io_requests);
+ spin_unlock(&netfs_proc_lock);
+}
+static inline void netfs_proc_del_rreq(struct netfs_io_request *rreq)
+{
+ if (!list_empty(&rreq->proc_link)) {
+ spin_lock(&netfs_proc_lock);
+ list_del_rcu(&rreq->proc_link);
+ spin_unlock(&netfs_proc_lock);
+ }
+}
+#else
+static inline void netfs_proc_add_rreq(struct netfs_io_request *rreq) {}
+static inline void netfs_proc_del_rreq(struct netfs_io_request *rreq) {}
+#endif

/*
* objects.c
diff --git a/fs/netfs/main.c b/fs/netfs/main.c
index c9af6e0896d3..97ce1436615b 100644
--- a/fs/netfs/main.c
+++ b/fs/netfs/main.c
@@ -21,13 +21,80 @@ unsigned netfs_debug;
module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");

+#ifdef CONFIG_PROC_FS
+LIST_HEAD(netfs_io_requests);
+DEFINE_SPINLOCK(netfs_proc_lock);
+
+static const char *netfs_origins[] = {
+ [NETFS_READAHEAD] = "RA",
+ [NETFS_READPAGE] = "RP",
+ [NETFS_READ_FOR_WRITE] = "RW",
+};
+
+/*
+ * Generate a list of I/O requests in /proc/fs/netfs/requests
+ */
+static int netfs_requests_seq_show(struct seq_file *m, void *v)
+{
+ struct netfs_io_request *rreq;
+
+ if (v == &netfs_io_requests) {
+ seq_puts(m,
+ "REQUEST OR REF FL ERR OPS COVERAGE\n"
+ "======== == === == ==== === =========\n"
+ );
+ return 0;
+ }
+
+ rreq = list_entry(v, struct netfs_io_request, proc_link);
+ seq_printf(m,
+ "%08x %s %3d %2lx %4d %3d @%04llx %zx/%zx",
+ rreq->debug_id,
+ netfs_origins[rreq->origin],
+ refcount_read(&rreq->ref),
+ rreq->flags,
+ rreq->error,
+ atomic_read(&rreq->nr_outstanding),
+ rreq->start, rreq->submitted, rreq->len);
+ seq_putc(m, '\n');
+ return 0;
+}
+
+static void *netfs_requests_seq_start(struct seq_file *m, loff_t *_pos)
+ __acquires(rcu)
+{
+ rcu_read_lock();
+ return seq_list_start_head(&netfs_io_requests, *_pos);
+}
+
+static void *netfs_requests_seq_next(struct seq_file *m, void *v, loff_t *_pos)
+{
+ return seq_list_next(v, &netfs_io_requests, _pos);
+}
+
+static void netfs_requests_seq_stop(struct seq_file *m, void *v)
+ __releases(rcu)
+{
+ rcu_read_unlock();
+}
+
+static const struct seq_operations netfs_requests_seq_ops = {
+ .start = netfs_requests_seq_start,
+ .next = netfs_requests_seq_next,
+ .stop = netfs_requests_seq_stop,
+ .show = netfs_requests_seq_show,
+};
+#endif /* CONFIG_PROC_FS */
+
static int __init netfs_init(void)
{
int ret = -ENOMEM;

if (!proc_mkdir("fs/netfs", NULL))
goto error;
-
+ if (!proc_create_seq("fs/netfs/requests", S_IFREG | 0444, NULL,
+ &netfs_requests_seq_ops))
+ goto error_proc;
#ifdef CONFIG_FSCACHE_STATS
if (!proc_create_single("fs/netfs/stats", S_IFREG | 0444, NULL,
netfs_stats_show))
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index e17cdf53f6a7..85f428fc52e6 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -45,6 +45,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
}
}

+ netfs_proc_add_rreq(rreq);
netfs_stat(&netfs_n_rh_rreq);
return rreq;
}
@@ -76,12 +77,13 @@ static void netfs_free_request(struct work_struct *work)
container_of(work, struct netfs_io_request, work);

trace_netfs_rreq(rreq, netfs_rreq_trace_free);
+ netfs_proc_del_rreq(rreq);
netfs_clear_subrequests(rreq, false);
if (rreq->netfs_ops->free_request)
rreq->netfs_ops->free_request(rreq);
if (rreq->cache_resources.ops)
rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
- kfree(rreq);
+ kfree_rcu(rreq, rcu);
netfs_stat_d(&netfs_n_rh_rreq);
}

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 32faf6c89702..7244ddebd974 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -175,10 +175,14 @@ enum netfs_io_origin {
* operations to a variety of data stores and then stitch the result together.
*/
struct netfs_io_request {
- struct work_struct work;
+ union {
+ struct work_struct work;
+ struct rcu_head rcu;
+ };
struct inode *inode; /* The file being accessed */
struct address_space *mapping; /* The mapping being accessed */
struct netfs_cache_resources cache_resources;
+ struct list_head proc_link; /* Link in netfs_iorequests */
struct list_head subrequests; /* Contributory I/O operations */
void *netfs_priv; /* Private data for the netfs */
unsigned int debug_id;