From: Mike Galbraith <[email protected]> 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] Cc: Minchan Kim <[email protected]> Cc: Nitin Gupta <[email protected]> Cc: Sergey Senozhatsky <[email protected]> Signed-off-by: Mike Galbraith <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- drivers/block/zram/zcomp.c | 17 ++++++++++------- drivers/block/zram/zcomp.h | 2 ++ 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index ae6dc137a1ed8..fa3485309735e 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -42,11 +42,11 @@ static void zcomp_strm_free(struct zcomp_strm *zstrm) } /* - * allocate new zcomp_strm structure with ->tfm initialized by - * backend, return NULL on error + * Initialize zcomp_strm structure with ->tfm initialized by + * backend, and ->buffer. Return a negative value on error. */ -static int zcomp_strm_alloc(struct zcomp_strm *zstrm, - struct zcomp *comp) +static int zcomp_strm_init(struct zcomp_strm *zstrm, + struct zcomp *comp) { zstrm->tfm = crypto_alloc_comp(comp->name, 0, 0); /* @@ -111,12 +111,13 @@ ssize_t zcomp_available_show(const char *comp, char *buf) struct zcomp_strm *zcomp_stream_get(struct zcomp *comp) { - return get_cpu_ptr(comp->stream); + local_lock(&comp->stream->lock); + return this_cpu_ptr(comp->stream); } void zcomp_stream_put(struct zcomp *comp) { - put_cpu_ptr(comp->stream); + local_unlock(&comp->stream->lock); } int zcomp_compress(struct zcomp_strm *zstrm, @@ -160,7 +161,9 @@ int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node) int ret; zstrm = per_cpu_ptr(comp->stream, cpu); - ret = zcomp_strm_alloc(zstrm, comp); + local_lock_init(&zstrm->lock); + + ret = zcomp_strm_init(zstrm, comp); if (ret) { pr_err("Can't allocate a compression stream\n"); return -ENOMEM; diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h index 72c2ee4d843ed..45c4c1858e5a9 100644 --- a/drivers/block/zram/zcomp.h +++ b/drivers/block/zram/zcomp.h @@ -5,11 +5,13 @@ #ifndef _ZCOMP_H_ #define _ZCOMP_H_ +#include <linux/locallock.h> struct zcomp_strm { /* compression/decompression buffer */ void *buffer; struct crypto_comp *tfm; + struct local_lock lock; }; /* dynamic per-device compression frontend */ -- 2.27.0.rc0
