/* 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)
*/
/* * 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 */ unsignedchar curr_slot; /* Folio currently being read */ unsignedchar 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)
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