3 files changed, 207 insertions, 0 deletions

diff --git a/include/linux/folio_queue.h b/include/linux/folio_queue.h
new file mode 100644
index 000000000000..52773613bf23
--- /dev/null
+++ b/include/linux/folio_queue.h
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Queue of folios definitions
+ *
+ * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_FOLIO_QUEUE_H
+#define _LINUX_FOLIO_QUEUE_H
+
+#include <linux/pagevec.h>
+
+/*
+ * Segment in a queue of running buffers.  Each segment can hold a number of
+ * folios and a portion of the queue can be referenced with the ITER_FOLIOQ
+ * iterator.  The possibility exists of inserting non-folio elements into the
+ * queue (such as gaps).
+ *
+ * Explicit prev and next pointers are used instead of a list_head to make it
+ * easier to add segments to tail and remove them from the head without the
+ * need for a lock.
+ */
+struct folio_queue {
+	struct folio_batch	vec;		/* Folios in the queue segment */
+	u8			orders[PAGEVEC_SIZE]; /* Order of each folio */
+	struct folio_queue	*next;		/* Next queue segment or NULL */
+	struct folio_queue	*prev;		/* Previous queue segment of NULL */
+	unsigned long		marks;		/* 1-bit mark per folio */
+	unsigned long		marks2;		/* Second 1-bit mark per folio */
+#if PAGEVEC_SIZE > BITS_PER_LONG
+#error marks is not big enough
+#endif
+};
+
+static inline void folioq_init(struct folio_queue *folioq)
+{
+	folio_batch_init(&folioq->vec);
+	folioq->next = NULL;
+	folioq->prev = NULL;
+	folioq->marks = 0;
+	folioq->marks2 = 0;
+}
+
+static inline unsigned int folioq_nr_slots(const struct folio_queue *folioq)
+{
+	return PAGEVEC_SIZE;
+}
+
+static inline unsigned int folioq_count(struct folio_queue *folioq)
+{
+	return folio_batch_count(&folioq->vec);
+}
+
+static inline bool folioq_full(struct folio_queue *folioq)
+{
+	//return !folio_batch_space(&folioq->vec);
+	return folioq_count(folioq) >= folioq_nr_slots(folioq);
+}
+
+static inline bool folioq_is_marked(const struct folio_queue *folioq, unsigned int slot)
+{
+	return test_bit(slot, &folioq->marks);
+}
+
+static inline void folioq_mark(struct folio_queue *folioq, unsigned int slot)
+{
+	set_bit(slot, &folioq->marks);
+}
+
+static inline void folioq_unmark(struct folio_queue *folioq, unsigned int slot)
+{
+	clear_bit(slot, &folioq->marks);
+}
+
+static inline bool folioq_is_marked2(const struct folio_queue *folioq, unsigned int slot)
+{
+	return test_bit(slot, &folioq->marks2);
+}
+
+static inline void folioq_mark2(struct folio_queue *folioq, unsigned int slot)
+{
+	set_bit(slot, &folioq->marks2);
+}
+
+static inline void folioq_unmark2(struct folio_queue *folioq, unsigned int slot)
+{
+	clear_bit(slot, &folioq->marks2);
+}
+
+static inline unsigned int __folio_order(struct folio *folio)
+{
+	if (!folio_test_large(folio))
+		return 0;
+	return folio->_flags_1 & 0xff;
+}
+
+static inline unsigned int folioq_append(struct folio_queue *folioq, struct folio *folio)
+{
+	unsigned int slot = folioq->vec.nr++;
+
+	folioq->vec.folios[slot] = folio;
+	folioq->orders[slot] = __folio_order(folio);
+	return slot;
+}
+
+static inline unsigned int folioq_append_mark(struct folio_queue *folioq, struct folio *folio)
+{
+	unsigned int slot = folioq->vec.nr++;
+
+	folioq->vec.folios[slot] = folio;
+	folioq->orders[slot] = __folio_order(folio);
+	folioq_mark(folioq, slot);
+	return slot;
+}
+
+static inline struct folio *folioq_folio(const struct folio_queue *folioq, unsigned int slot)
+{
+	return folioq->vec.folios[slot];
+}
+
+static inline unsigned int folioq_folio_order(const struct folio_queue *folioq, unsigned int slot)
+{
+	return folioq->orders[slot];
+}
+
+static inline size_t folioq_folio_size(const struct folio_queue *folioq, unsigned int slot)
+{
+	return PAGE_SIZE << folioq_folio_order(folioq, slot);
+}
+
+static inline void folioq_clear(struct folio_queue *folioq, unsigned int slot)
+{
+	folioq->vec.folios[slot] = NULL;
+	folioq_unmark(folioq, slot);
+	folioq_unmark2(folioq, slot);
+}
+
+#endif /* _LINUX_FOLIO_QUEUE_H */
diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
index 270454a6703d..a223370a59a7 100644
--- a/include/linux/iov_iter.h
+++ b/include/linux/iov_iter.h
@@ -10,6 +10,7 @@
 
 #include <linux/uio.h>
 #include <linux/bvec.h>
+#include <linux/folio_queue.h>
 
 typedef size_t (*iov_step_f)(void *iter_base, size_t progress, size_t len,
 			     void *priv, void *priv2);
@@ -141,6 +142,60 @@ size_t iterate_bvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
 }
 
 /*
+ * Handle ITER_FOLIOQ.
+ */
+static __always_inline
+size_t iterate_folioq(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		      iov_step_f step)
+{
+	const struct folio_queue *folioq = iter->folioq;
+	unsigned int slot = iter->folioq_slot;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	if (slot == folioq_nr_slots(folioq)) {
+		/* The iterator may have been extended. */
+		folioq = folioq->next;
+		slot = 0;
+	}
+
+	do {
+		struct folio *folio = folioq_folio(folioq, slot);
+		size_t part, remain, consumed;
+		size_t fsize;
+		void *base;
+
+		if (!folio)
+			break;
+
+		fsize = folioq_folio_size(folioq, slot);
+		base = kmap_local_folio(folio, skip);
+		part = umin(len, PAGE_SIZE - skip % PAGE_SIZE);
+		remain = step(base, progress, part, priv, priv2);
+		kunmap_local(base);
+		consumed = part - remain;
+		len -= consumed;
+		progress += consumed;
+		skip += consumed;
+		if (skip >= fsize) {
+			skip = 0;
+			slot++;
+			if (slot == folioq_nr_slots(folioq) && folioq->next) {
+				folioq = folioq->next;
+				slot = 0;
+			}
+		}
+		if (remain)
+			break;
+	} while (len);
+
+	iter->folioq_slot = slot;
+	iter->folioq = folioq;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
  * Handle ITER_XARRAY.
  */
 static __always_inline
@@ -249,6 +304,8 @@ size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv,
 		return iterate_bvec(iter, len, priv, priv2, step);
 	if (iov_iter_is_kvec(iter))
 		return iterate_kvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_folioq(iter))
+		return iterate_folioq(iter, len, priv, priv2, step);
 	if (iov_iter_is_xarray(iter))
 		return iterate_xarray(iter, len, priv, priv2, step);
 	return iterate_discard(iter, len, priv, priv2, step);
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 7020adedfa08..845d110acadc 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -11,6 +11,7 @@
 #include <uapi/linux/uio.h>
 
 struct page;
+struct folio_queue;
 
 typedef unsigned int __bitwise iov_iter_extraction_t;
 
@@ -25,6 +26,7 @@ enum iter_type {
 	ITER_IOVEC,
 	ITER_BVEC,
 	ITER_KVEC,
+	ITER_FOLIOQ,
 	ITER_XARRAY,
 	ITER_DISCARD,
 };
@@ -66,6 +68,7 @@ struct iov_iter {
 				const struct iovec *__iov;
 				const struct kvec *kvec;
 				const struct bio_vec *bvec;
+				const struct folio_queue *folioq;
 				struct xarray *xarray;
 				void __user *ubuf;
 			};
@@ -74,6 +77,7 @@ struct iov_iter {
 	};
 	union {
 		unsigned long nr_segs;
+		u8 folioq_slot;
 		loff_t xarray_start;
 	};
 };
@@ -126,6 +130,11 @@ static inline bool iov_iter_is_discard(const struct iov_iter *i)
 	return iov_iter_type(i) == ITER_DISCARD;
 }
 
+static inline bool iov_iter_is_folioq(const struct iov_iter *i)
+{
+	return iov_iter_type(i) == ITER_FOLIOQ;
+}
+
 static inline bool iov_iter_is_xarray(const struct iov_iter *i)
 {
 	return iov_iter_type(i) == ITER_XARRAY;
@@ -273,6 +282,9 @@ void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec
 void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
 			unsigned long nr_segs, size_t count);
 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
+void iov_iter_folio_queue(struct iov_iter *i, unsigned int direction,
+			  const struct folio_queue *folioq,
+			  unsigned int first_slot, unsigned int offset, size_t count);
 void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
 		     loff_t start, size_t count);
 ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,