1 files changed, 227 insertions, 0 deletions
diff --git a/fs/netfs/read_pgpriv2.c b/fs/netfs/read_pgpriv2.c
new file mode 100644
index 000000000000..cf7727060215
--- /dev/null
+++ b/fs/netfs/read_pgpriv2.c
@@ -0,0 +1,227 @@
+// 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) < 0) {
+		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;
+
+	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_request(creq, false, netfs_rreq_trace_put_return);
+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);
+
+	netfs_put_request(creq, false, 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;
+}