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C
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162/* SPDX-License-Identifier: GPL-2.0-or-later *//* Rolling buffer of folios * * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) */
#ifndef _ROLLING_BUFFER_H#define _ROLLING_BUFFER_H
#include <linux/folio_queue.h>#include <linux/uio.h>
/* * Rolling buffer. Whilst the buffer is live and in use, folios and folio * queue segments can be added to one end by one thread and removed from the * other end by another thread. The buffer isn't allowed to be empty; it must * always have at least one folio_queue in it so that neither side has to * modify both queue pointers. * * The iterator in the buffer is extended as buffers are inserted. It can be * snapshotted to use a segment of the buffer. */struct rolling_buffer { struct folio_queue *head; /* Producer's insertion point */ struct folio_queue *tail; /* Consumer's removal point */ struct iov_iter iter; /* Iterator tracking what's left in the buffer */ u8 next_head_slot; /* Next slot in ->head */ u8 first_tail_slot; /* First slot in ->tail */};
/* * Snapshot of a rolling buffer. */struct rolling_buffer_snapshot { struct folio_queue *curr_folioq; /* Queue segment in which current folio resides */ unsigned char curr_slot; /* Folio currently being read */ unsigned char curr_order; /* Order of folio */};
/* Marks to store per-folio in the internal folio_queue structs. */#define ROLLBUF_MARK_1 BIT(0)#define ROLLBUF_MARK_2 BIT(1)
int rolling_buffer_init(struct rolling_buffer *roll, unsigned int rreq_id, unsigned int direction, gfp_t gfp);int rolling_buffer_make_space(struct rolling_buffer *roll, gfp_t gfp);ssize_t rolling_buffer_bulk_load_from_ra(struct rolling_buffer *roll, struct readahead_control *ractl, unsigned int rreq_id, gfp_t gfp);ssize_t rolling_buffer_append(struct rolling_buffer *roll, struct folio *folio, unsigned int flags, gfp_t gfp);struct folio_queue *rolling_buffer_delete_spent(struct rolling_buffer *roll);void rolling_buffer_clear(struct rolling_buffer *roll);
static inline void rolling_buffer_advance(struct rolling_buffer *roll, size_t amount){ iov_iter_advance(&roll->iter, amount);}
#endif /* _ROLLING_BUFFER_H */