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, 387 insertions, 0 deletions

diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
new file mode 100644
index 000000000..c16fbad28
--- /dev/null
+++ b/fs/netfs/direct_write.c
@@ -0,0 +1,387 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Unbuffered and direct write support.
+ *
+ * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/uio.h>
+#include "internal.h"
+
+/*
+ * Perform the cleanup rituals after an unbuffered write is complete.
+ */
+static void netfs_unbuffered_write_done(struct netfs_io_request *wreq)
+{
+	struct netfs_inode *ictx = netfs_inode(wreq->inode);
+
+	_enter("R=%x", wreq->debug_id);
+
+	/* Okay, declare that all I/O is complete. */
+	trace_netfs_rreq(wreq, netfs_rreq_trace_write_done);
+
+	if (!wreq->error)
+		netfs_update_i_size(ictx, &ictx->inode, wreq->start, wreq->transferred);
+
+	if (wreq->origin == NETFS_DIO_WRITE &&
+	    wreq->mapping->nrpages) {
+		/* mmap may have got underfoot and we may now have folios
+		 * locally covering the region we just wrote.  Attempt to
+		 * discard the folios, but leave in place any modified locally.
+		 * ->write_iter() is prevented from interfering by the DIO
+		 * counter.
+		 */
+		pgoff_t first = wreq->start >> PAGE_SHIFT;
+		pgoff_t last = (wreq->start + wreq->transferred - 1) >> PAGE_SHIFT;
+
+		invalidate_inode_pages2_range(wreq->mapping, first, last);
+	}
+
+	if (wreq->origin == NETFS_DIO_WRITE)
+		inode_dio_end(wreq->inode);
+
+	_debug("finished");
+	netfs_wake_rreq_flag(wreq, NETFS_RREQ_IN_PROGRESS, netfs_rreq_trace_wake_ip);
+	/* As we cleared NETFS_RREQ_IN_PROGRESS, we acquired its ref. */
+
+	if (wreq->iocb) {
+		size_t written = umin(wreq->transferred, wreq->len);
+
+		wreq->iocb->ki_pos += written;
+		if (wreq->iocb->ki_complete) {
+			trace_netfs_rreq(wreq, netfs_rreq_trace_ki_complete);
+			wreq->iocb->ki_complete(wreq->iocb, wreq->error ?: written);
+		}
+		wreq->iocb = VFS_PTR_POISON;
+	}
+
+	netfs_clear_subrequests(wreq);
+}
+
+/*
+ * Collect the subrequest results of unbuffered write subrequests.
+ */
+static void netfs_unbuffered_write_collect(struct netfs_io_request *wreq,
+					   struct netfs_io_stream *stream,
+					   struct netfs_io_subrequest *subreq)
+{
+	trace_netfs_collect_sreq(wreq, subreq);
+
+	spin_lock(&wreq->lock);
+	list_del_init(&subreq->rreq_link);
+	spin_unlock(&wreq->lock);
+
+	wreq->transferred += subreq->transferred;
+	iov_iter_advance(&wreq->buffer.iter, subreq->transferred);
+
+	stream->collected_to = subreq->start + subreq->transferred;
+	wreq->collected_to = stream->collected_to;
+	netfs_put_subrequest(subreq, netfs_sreq_trace_put_done);
+
+	trace_netfs_collect_stream(wreq, stream);
+	trace_netfs_collect_state(wreq, wreq->collected_to, 0);
+}
+
+/*
+ * Write data to the server without going through the pagecache and without
+ * writing it to the local cache.  We dispatch the subrequests serially and
+ * wait for each to complete before dispatching the next, lest we leave a gap
+ * in the data written due to a failure such as ENOSPC.  We could, however
+ * attempt to do preparation such as content encryption for the next subreq
+ * whilst the current is in progress.
+ */
+static int netfs_unbuffered_write(struct netfs_io_request *wreq)
+{
+	struct netfs_io_subrequest *subreq = NULL;
+	struct netfs_io_stream *stream = &wreq->io_streams[0];
+	int ret;
+
+	_enter("%llx", wreq->len);
+
+	if (wreq->origin == NETFS_DIO_WRITE)
+		inode_dio_begin(wreq->inode);
+
+	stream->collected_to = wreq->start;
+
+	for (;;) {
+		bool retry = false;
+
+		if (!subreq) {
+			netfs_prepare_write(wreq, stream, wreq->start + wreq->transferred);
+			subreq = stream->construct;
+			stream->construct = NULL;
+		}
+
+		/* Check if (re-)preparation failed. */
+		if (unlikely(test_bit(NETFS_SREQ_FAILED, &subreq->flags))) {
+			netfs_write_subrequest_terminated(subreq, subreq->error);
+			wreq->error = subreq->error;
+			break;
+		}
+
+		iov_iter_truncate(&subreq->io_iter, wreq->len - wreq->transferred);
+		if (!iov_iter_count(&subreq->io_iter))
+			break;
+
+		subreq->len = netfs_limit_iter(&subreq->io_iter, 0,
+					       stream->sreq_max_len,
+					       stream->sreq_max_segs);
+		iov_iter_truncate(&subreq->io_iter, subreq->len);
+		stream->submit_extendable_to = subreq->len;
+
+		trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
+		stream->issue_write(subreq);
+
+		/* Async, need to wait. */
+		netfs_wait_for_in_progress_stream(wreq, stream);
+
+		if (test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) {
+			retry = true;
+		} else if (test_bit(NETFS_SREQ_FAILED, &subreq->flags)) {
+			ret = subreq->error;
+			wreq->error = ret;
+			netfs_see_subrequest(subreq, netfs_sreq_trace_see_failed);
+			subreq = NULL;
+			break;
+		}
+		ret = 0;
+
+		if (!retry) {
+			netfs_unbuffered_write_collect(wreq, stream, subreq);
+			subreq = NULL;
+			if (wreq->transferred >= wreq->len)
+				break;
+			if (!wreq->iocb && signal_pending(current)) {
+				ret = wreq->transferred ? -EINTR : -ERESTARTSYS;
+				trace_netfs_rreq(wreq, netfs_rreq_trace_intr);
+				break;
+			}
+			continue;
+		}
+
+		/* We need to retry the last subrequest, so first reset the
+		 * iterator, taking into account what, if anything, we managed
+		 * to transfer.
+		 */
+		subreq->error = -EAGAIN;
+		trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
+		if (subreq->transferred > 0) {
+			iov_iter_advance(&wreq->buffer.iter, subreq->transferred);
+			wreq->transferred += subreq->transferred;
+		}
+
+		if (stream->source == NETFS_UPLOAD_TO_SERVER &&
+		    wreq->netfs_ops->retry_request)
+			wreq->netfs_ops->retry_request(wreq, stream);
+
+		__clear_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
+		__clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
+		__clear_bit(NETFS_SREQ_BOUNDARY, &subreq->flags);
+		__clear_bit(NETFS_SREQ_FAILED, &subreq->flags);
+		subreq->io_iter		= wreq->buffer.iter;
+		subreq->start		= wreq->start + wreq->transferred;
+		subreq->len		= wreq->len   - wreq->transferred;
+		subreq->transferred	= 0;
+		subreq->retry_count	+= 1;
+		stream->sreq_max_len	= UINT_MAX;
+		stream->sreq_max_segs	= INT_MAX;
+
+		netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
+
+		if (stream->prepare_write)
+			stream->prepare_write(subreq);
+		__set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
+		netfs_stat(&netfs_n_wh_retry_write_subreq);
+	}
+
+	netfs_unbuffered_write_done(wreq);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+static void netfs_unbuffered_write_async(struct work_struct *work)
+{
+	struct netfs_io_request *wreq = container_of(work, struct netfs_io_request, work);
+
+	netfs_unbuffered_write(wreq);
+	netfs_put_request(wreq, netfs_rreq_trace_put_complete);
+}
+
+/*
+ * Perform an unbuffered write where we may have to do an RMW operation on an
+ * encrypted file.  This can also be used for direct I/O writes.
+ */
+ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *iter,
+						  struct netfs_group *netfs_group)
+{
+	struct netfs_io_request *wreq;
+	unsigned long long start = iocb->ki_pos;
+	unsigned long long end = start + iov_iter_count(iter);
+	ssize_t ret, n;
+	size_t len = iov_iter_count(iter);
+	bool async = !is_sync_kiocb(iocb);
+
+	_enter("");
+
+	/* We're going to need a bounce buffer if what we transmit is going to
+	 * be different in some way to the source buffer, e.g. because it gets
+	 * encrypted/compressed or because it needs expanding to a block size.
+	 */
+	// TODO
+
+	_debug("uw %llx-%llx", start, end);
+
+	wreq = netfs_create_write_req(iocb->ki_filp->f_mapping, iocb->ki_filp, start,
+				      iocb->ki_flags & IOCB_DIRECT ?
+				      NETFS_DIO_WRITE : NETFS_UNBUFFERED_WRITE);
+	if (IS_ERR(wreq))
+		return PTR_ERR(wreq);
+
+	wreq->io_streams[0].avail = true;
+	trace_netfs_write(wreq, (iocb->ki_flags & IOCB_DIRECT ?
+				 netfs_write_trace_dio_write :
+				 netfs_write_trace_unbuffered_write));
+
+	{
+		/* If this is an async op and we're not using a bounce buffer,
+		 * we have to save the source buffer as the iterator is only
+		 * good until we return.  In such a case, extract an iterator
+		 * to represent as much of the the output buffer as we can
+		 * manage.  Note that the extraction might not be able to
+		 * allocate a sufficiently large bvec array and may shorten the
+		 * request.
+		 */
+		if (user_backed_iter(iter)) {
+			n = netfs_extract_user_iter(iter, len, &wreq->buffer.iter, 0);
+			if (n < 0) {
+				ret = n;
+				goto error_put;
+			}
+			wreq->direct_bv = (struct bio_vec *)wreq->buffer.iter.bvec;
+			wreq->direct_bv_count = n;
+			wreq->direct_bv_unpin = iov_iter_extract_will_pin(iter);
+		} else {
+			/* If this is a kernel-generated async DIO request,
+			 * assume that any resources the iterator points to
+			 * (eg. a bio_vec array) will persist till the end of
+			 * the op.
+			 */
+			wreq->buffer.iter = *iter;
+		}
+
+		wreq->len = iov_iter_count(&wreq->buffer.iter);
+	}
+
+	__set_bit(NETFS_RREQ_USE_IO_ITER, &wreq->flags);
+
+	/* Copy the data into the bounce buffer and encrypt it. */
+	// TODO
+
+	/* Dispatch the write. */
+	__set_bit(NETFS_RREQ_UPLOAD_TO_SERVER, &wreq->flags);
+
+	if (async) {
+		INIT_WORK(&wreq->work, netfs_unbuffered_write_async);
+		wreq->iocb = iocb;
+		queue_work(system_dfl_wq, &wreq->work);
+		ret = -EIOCBQUEUED;
+	} else {
+		ret = netfs_unbuffered_write(wreq);
+		if (ret < 0) {
+			_debug("begin = %zd", ret);
+		} else {
+			iocb->ki_pos += wreq->transferred;
+			ret = wreq->transferred ?: wreq->error;
+		}
+
+		netfs_put_request(wreq, netfs_rreq_trace_put_complete);
+	}
+
+	netfs_put_request(wreq, netfs_rreq_trace_put_return);
+	return ret;
+
+error_put:
+	netfs_put_failed_request(wreq);
+	return ret;
+}
+EXPORT_SYMBOL(netfs_unbuffered_write_iter_locked);
+
+/**
+ * netfs_unbuffered_write_iter - Unbuffered write to a file
+ * @iocb: IO state structure
+ * @from: iov_iter with data to write
+ *
+ * Do an unbuffered write to a file, writing the data directly to the server
+ * and not lodging the data in the pagecache.
+ *
+ * Return:
+ * * Negative error code if no data has been written at all of
+ *   vfs_fsync_range() failed for a synchronous write
+ * * Number of bytes written, even for truncated writes
+ */
+ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	struct netfs_inode *ictx = netfs_inode(inode);
+	ssize_t ret;
+	loff_t pos = iocb->ki_pos;
+	unsigned long long end = pos + iov_iter_count(from) - 1;
+
+	_enter("%llx,%zx,%llx", pos, iov_iter_count(from), i_size_read(inode));
+
+	if (!iov_iter_count(from))
+		return 0;
+
+	trace_netfs_write_iter(iocb, from);
+	netfs_stat(&netfs_n_wh_dio_write);
+
+	ret = netfs_start_io_direct(inode);
+	if (ret < 0)
+		return ret;
+	ret = generic_write_checks(iocb, from);
+	if (ret <= 0)
+		goto out;
+	ret = file_remove_privs(file);
+	if (ret < 0)
+		goto out;
+	ret = file_update_time(file);
+	if (ret < 0)
+		goto out;
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		/* We could block if there are any pages in the range. */
+		ret = -EAGAIN;
+		if (filemap_range_has_page(mapping, pos, end))
+			if (filemap_invalidate_inode(inode, true, pos, end))
+				goto out;
+	} else {
+		ret = filemap_write_and_wait_range(mapping, pos, end);
+		if (ret < 0)
+			goto out;
+	}
+
+	/*
+	 * After a write we want buffered reads to be sure to go to disk to get
+	 * the new data.  We invalidate clean cached page from the region we're
+	 * about to write.  We do this *before* the write so that we can return
+	 * without clobbering -EIOCBQUEUED from ->direct_IO().
+	 */
+	ret = filemap_invalidate_inode(inode, true, pos, end);
+	if (ret < 0)
+		goto out;
+	end = iocb->ki_pos + iov_iter_count(from);
+	spin_lock(&inode->i_lock);
+	if (end > ictx->_zero_point)
+		netfs_write_zero_point(inode, end);
+	spin_unlock(&inode->i_lock);
+
+	fscache_invalidate(netfs_i_cookie(ictx), NULL, i_size_read(inode),
+			   FSCACHE_INVAL_DIO_WRITE);
+	ret = netfs_unbuffered_write_iter_locked(iocb, from, NULL);
+out:
+	netfs_end_io_direct(inode);
+	return ret;
+}
+EXPORT_SYMBOL(netfs_unbuffered_write_iter);