ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 233 insertions, 0 deletions

diff --git a/fs/netfs/read_pgpriv2.c b/fs/netfs/read_pgpriv2.c
new file mode 100644
index 000000000..c31190993
--- /dev/null
+++ b/fs/netfs/read_pgpriv2.c
@@ -0,0 +1,233 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Read with PG_private_2 [DEPRECATED].
+ *
+ * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/task_io_accounting_ops.h>
+#include "internal.h"
+
+/*
+ * [DEPRECATED] Copy a folio to the cache with PG_private_2 set.
+ */
+static void netfs_pgpriv2_copy_folio(struct netfs_io_request *creq, struct folio *folio)
+{
+	struct netfs_io_stream *cache = &creq->io_streams[1];
+	size_t fsize = folio_size(folio), flen = fsize;
+	loff_t fpos = folio_pos(folio), i_size;
+	bool to_eof = false;
+
+	_enter("");
+
+	/* netfs_perform_write() may shift i_size around the page or from out
+	 * of the page to beyond it, but cannot move i_size into or through the
+	 * page since we have it locked.
+	 */
+	i_size = i_size_read(creq->inode);
+
+	if (fpos >= i_size) {
+		/* mmap beyond eof. */
+		_debug("beyond eof");
+		folio_end_private_2(folio);
+		return;
+	}
+
+	if (fpos + fsize > creq->i_size)
+		creq->i_size = i_size;
+
+	if (flen > i_size - fpos) {
+		flen = i_size - fpos;
+		to_eof = true;
+	} else if (flen == i_size - fpos) {
+		to_eof = true;
+	}
+
+	_debug("folio %zx %zx", flen, fsize);
+
+	trace_netfs_folio(folio, netfs_folio_trace_store_copy);
+
+	/* Attach the folio to the rolling buffer. */
+	if (rolling_buffer_append(&creq->buffer, folio, 0, creq->gfp) < 0) {
+		folio_end_private_2(folio);
+		clear_bit(NETFS_RREQ_FOLIO_COPY_TO_CACHE, &creq->flags);
+		return;
+	}
+
+	cache->submit_extendable_to = fsize;
+	cache->submit_off = 0;
+	cache->submit_len = flen;
+
+	/* Attach the folio to one or more subrequests.  For a big folio, we
+	 * could end up with thousands of subrequests if the wsize is small -
+	 * but we might need to wait during the creation of subrequests for
+	 * network resources (eg. SMB credits).
+	 */
+	do {
+		ssize_t part;
+
+		creq->buffer.iter.iov_offset = cache->submit_off;
+
+		atomic64_set(&creq->issued_to, fpos + cache->submit_off);
+		cache->submit_extendable_to = fsize - cache->submit_off;
+		part = netfs_advance_write(creq, cache, fpos + cache->submit_off,
+					   cache->submit_len, to_eof);
+		cache->submit_off += part;
+		if (part > cache->submit_len)
+			cache->submit_len = 0;
+		else
+			cache->submit_len -= part;
+	} while (cache->submit_len > 0);
+
+	creq->buffer.iter.iov_offset = 0;
+	rolling_buffer_advance(&creq->buffer, fsize);
+	atomic64_set(&creq->issued_to, fpos + fsize);
+
+	if (flen < fsize)
+		netfs_issue_write(creq, cache);
+}
+
+/*
+ * [DEPRECATED] Set up copying to the cache.
+ */
+static struct netfs_io_request *netfs_pgpriv2_begin_copy_to_cache(
+	struct netfs_io_request *rreq, struct folio *folio)
+{
+	struct netfs_io_request *creq;
+
+	if (!fscache_resources_valid(&rreq->cache_resources))
+		goto cancel;
+
+	creq = netfs_create_write_req(rreq->mapping, NULL, folio_pos(folio),
+				      NETFS_PGPRIV2_COPY_TO_CACHE);
+	if (IS_ERR(creq))
+		goto cancel;
+
+	if (!creq->io_streams[1].avail)
+		goto cancel_put;
+
+	__set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &creq->flags);
+	trace_netfs_copy2cache(rreq, creq);
+	trace_netfs_write(creq, netfs_write_trace_copy_to_cache);
+	netfs_stat(&netfs_n_wh_copy_to_cache);
+	rreq->copy_to_cache = creq;
+	return creq;
+
+cancel_put:
+	netfs_put_failed_request(creq);
+cancel:
+	rreq->copy_to_cache = ERR_PTR(-ENOBUFS);
+	clear_bit(NETFS_RREQ_FOLIO_COPY_TO_CACHE, &rreq->flags);
+	return ERR_PTR(-ENOBUFS);
+}
+
+/*
+ * [DEPRECATED] Mark page as requiring copy-to-cache using PG_private_2 and add
+ * it to the copy write request.
+ */
+void netfs_pgpriv2_copy_to_cache(struct netfs_io_request *rreq, struct folio *folio)
+{
+	struct netfs_io_request *creq = rreq->copy_to_cache;
+
+	if (!creq)
+		creq = netfs_pgpriv2_begin_copy_to_cache(rreq, folio);
+	if (IS_ERR(creq))
+		return;
+
+	trace_netfs_folio(folio, netfs_folio_trace_copy_to_cache);
+	folio_start_private_2(folio);
+	netfs_pgpriv2_copy_folio(creq, folio);
+}
+
+/*
+ * [DEPRECATED] End writing to the cache, flushing out any outstanding writes.
+ */
+void netfs_pgpriv2_end_copy_to_cache(struct netfs_io_request *rreq)
+{
+	struct netfs_io_request *creq = rreq->copy_to_cache;
+
+	if (IS_ERR_OR_NULL(creq))
+		return;
+
+	netfs_issue_write(creq, &creq->io_streams[1]);
+	smp_wmb(); /* Write lists before ALL_QUEUED. */
+	set_bit(NETFS_RREQ_ALL_QUEUED, &creq->flags);
+	trace_netfs_rreq(rreq, netfs_rreq_trace_end_copy_to_cache);
+	if (list_empty_careful(&creq->io_streams[1].subrequests))
+		netfs_wake_collector(creq);
+
+	netfs_put_request(creq, netfs_rreq_trace_put_return);
+	creq->copy_to_cache = NULL;
+}
+
+/*
+ * [DEPRECATED] Remove the PG_private_2 mark from any folios we've finished
+ * copying.
+ */
+bool netfs_pgpriv2_unlock_copied_folios(struct netfs_io_request *creq)
+{
+	struct folio_queue *folioq = creq->buffer.tail;
+	unsigned long long collected_to = creq->collected_to;
+	unsigned int slot = creq->buffer.first_tail_slot;
+	bool made_progress = false;
+
+	if (slot >= folioq_nr_slots(folioq)) {
+		folioq = rolling_buffer_delete_spent(&creq->buffer);
+		slot = 0;
+	}
+
+	for (;;) {
+		struct folio *folio;
+		unsigned long long fpos, fend;
+		size_t fsize, flen;
+
+		folio = folioq_folio(folioq, slot);
+		if (WARN_ONCE(!folio_test_private_2(folio),
+			      "R=%08x: folio %lx is not marked private_2\n",
+			      creq->debug_id, folio->index))
+			trace_netfs_folio(folio, netfs_folio_trace_not_under_wback);
+
+		fpos = folio_pos(folio);
+		fsize = folio_size(folio);
+		flen = fsize;
+
+		fend = min_t(unsigned long long, fpos + flen, creq->i_size);
+
+		trace_netfs_collect_folio(creq, folio, fend, collected_to);
+
+		/* Unlock any folio we've transferred all of. */
+		if (collected_to < fend)
+			break;
+
+		trace_netfs_folio(folio, netfs_folio_trace_end_copy);
+		folio_end_private_2(folio);
+		creq->cleaned_to = fpos + fsize;
+		made_progress = true;
+
+		/* Clean up the head folioq.  If we clear an entire folioq, then
+		 * we can get rid of it provided it's not also the tail folioq
+		 * being filled by the issuer.
+		 */
+		folioq_clear(folioq, slot);
+		slot++;
+		if (slot >= folioq_nr_slots(folioq)) {
+			folioq = rolling_buffer_delete_spent(&creq->buffer);
+			if (!folioq)
+				goto done;
+			slot = 0;
+		}
+
+		if (fpos + fsize >= collected_to)
+			break;
+	}
+
+	creq->buffer.tail = folioq;
+done:
+	creq->buffer.first_tail_slot = slot;
+	return made_progress;
+}