linux/drivers/block/zram/zcomp.h
Mike Galbraith 19f545b6e0 zram: Use local lock to protect per-CPU data
The zcomp driver uses per-CPU compression. The per-CPU data pointer is
acquired with get_cpu_ptr() which implicitly disables preemption.
It allocates memory inside the preempt disabled region which conflicts
with the PREEMPT_RT semantics.

Replace the implicit preemption control with an explicit local lock.
This allows RT kernels to substitute it with a real per CPU lock, which
serializes the access but keeps the code section preemptible. On non RT
kernels this maps to preempt_disable() as before, i.e. no functional
change.

[bigeasy: Use local_lock(), description, drop reordering]

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200527201119.1692513-8-bigeasy@linutronix.de
2020-05-28 10:31:10 +02:00

44 lines
1.2 KiB
C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright (C) 2014 Sergey Senozhatsky.
*/
#ifndef _ZCOMP_H_
#define _ZCOMP_H_
#include <linux/local_lock.h>
struct zcomp_strm {
/* The members ->buffer and ->tfm are protected by ->lock. */
local_lock_t lock;
/* compression/decompression buffer */
void *buffer;
struct crypto_comp *tfm;
};
/* dynamic per-device compression frontend */
struct zcomp {
struct zcomp_strm __percpu *stream;
const char *name;
struct hlist_node node;
};
int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node);
int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node);
ssize_t zcomp_available_show(const char *comp, char *buf);
bool zcomp_available_algorithm(const char *comp);
struct zcomp *zcomp_create(const char *comp);
void zcomp_destroy(struct zcomp *comp);
struct zcomp_strm *zcomp_stream_get(struct zcomp *comp);
void zcomp_stream_put(struct zcomp *comp);
int zcomp_compress(struct zcomp_strm *zstrm,
const void *src, unsigned int *dst_len);
int zcomp_decompress(struct zcomp_strm *zstrm,
const void *src, unsigned int src_len, void *dst);
bool zcomp_set_max_streams(struct zcomp *comp, int num_strm);
#endif /* _ZCOMP_H_ */