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From: Mike Galbraith <umgwanakikbuti@gmail.com>
Date: Thu, 20 Oct 2016 11:15:22 +0200
Subject: [PATCH] drivers/zram: Don't disable preemption in
zcomp_stream_get/put()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.10-rt5.tar.xz
In v4.7, the driver switched to percpu compression streams, disabling
preemption via get/put_cpu_ptr(). Use a per-zcomp_strm lock here. We
also have to fix an lock order issue in zram_decompress_page() such
that zs_map_object() nests inside of zcomp_stream_put() as it does in
zram_bvec_write().
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
[bigeasy: get_locked_var() -> per zcomp_strm lock]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/block/zram/zcomp.c | 13 +++++++++++--
drivers/block/zram/zcomp.h | 1 +
drivers/block/zram/zram_drv.c | 5 +++--
3 files changed, 15 insertions(+), 4 deletions(-)
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -113,12 +113,20 @@ ssize_t zcomp_available_show(const char
struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
{
- return *get_cpu_ptr(comp->stream);
+ struct zcomp_strm *zstrm;
+
+ zstrm = *get_local_ptr(comp->stream);
+ spin_lock(&zstrm->zcomp_lock);
+ return zstrm;
}
void zcomp_stream_put(struct zcomp *comp)
{
- put_cpu_ptr(comp->stream);
+ struct zcomp_strm *zstrm;
+
+ zstrm = *this_cpu_ptr(comp->stream);
+ spin_unlock(&zstrm->zcomp_lock);
+ put_local_ptr(zstrm);
}
int zcomp_compress(struct zcomp_strm *zstrm,
@@ -168,6 +176,7 @@ int zcomp_cpu_up_prepare(unsigned int cp
pr_err("Can't allocate a compression stream\n");
return -ENOMEM;
}
+ spin_lock_init(&zstrm->zcomp_lock);
*per_cpu_ptr(comp->stream, cpu) = zstrm;
return 0;
}
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -10,6 +10,7 @@ struct zcomp_strm {
/* compression/decompression buffer */
void *buffer;
struct crypto_comp *tfm;
+ spinlock_t zcomp_lock;
};
/* dynamic per-device compression frontend */
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1252,6 +1252,7 @@ static int __zram_bvec_read(struct zram
unsigned long handle;
unsigned int size;
void *src, *dst;
+ struct zcomp_strm *zstrm;
zram_slot_lock(zram, index);
if (zram_test_flag(zram, index, ZRAM_WB)) {
@@ -1282,6 +1283,7 @@ static int __zram_bvec_read(struct zram
size = zram_get_obj_size(zram, index);
+ zstrm = zcomp_stream_get(zram->comp);
src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
if (size == PAGE_SIZE) {
dst = kmap_atomic(page);
@@ -1289,14 +1291,13 @@ static int __zram_bvec_read(struct zram
kunmap_atomic(dst);
ret = 0;
} else {
- struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp);
dst = kmap_atomic(page);
ret = zcomp_decompress(zstrm, src, size, dst);
kunmap_atomic(dst);
- zcomp_stream_put(zram->comp);
}
zs_unmap_object(zram->mem_pool, handle);
+ zcomp_stream_put(zram->comp);
zram_slot_unlock(zram, index);
/* Should NEVER happen. Return bio error if it does. */
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