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authorMike Galbraith <umgwanakikbuti@gmail.com>2020-05-27 23:11:19 +0300
committerIngo Molnar <mingo@kernel.org>2020-05-28 11:31:10 +0300
commit19f545b6e07f753c4dc639c2f0ab52345733b6a8 (patch)
tree0280ea9f67d39a48f67716bf9fdf4d3554c93cf4 /drivers/block
parented19f19256be2949af1ab5634e62178d30a355c2 (diff)
downloadlinux-19f545b6e07f753c4dc639c2f0ab52345733b6a8.tar.xz
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
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/zram/zcomp.c7
-rw-r--r--drivers/block/zram/zcomp.h3
2 files changed, 8 insertions, 2 deletions
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 912e3e63d8a0..5ee8e3fae551 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -110,12 +110,13 @@ 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,
@@ -159,6 +160,8 @@ int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
int ret;
zstrm = per_cpu_ptr(comp->stream, cpu);
+ local_lock_init(&zstrm->lock);
+
ret = zcomp_strm_init(zstrm, comp);
if (ret)
pr_err("Can't allocate a compression stream\n");
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 72c2ee4d843e..40f6420f4b2e 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -5,8 +5,11 @@
#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;