zram: Fix __zram_bvec_{read,write}() locking order
Mikhail reported a lockdep spat detailing how __zram_bvec_read() and
__zram_bvec_write() use zstrm->lock and zspage->lock in opposite order.
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index bff3d40..e132014 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1218,10 +1218,11 @@ static void zram_free_page(struct zram *zram, size_t index)
static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
struct bio *bio, bool partial_io)
{
- int ret;
+ struct zcomp_strm *zstrm;
unsigned long handle;
unsigned int size;
void *src, *dst;
+ int ret;
zram_slot_lock(zram, index);
if (zram_test_flag(zram, index, ZRAM_WB)) {
@@ -1252,6 +1253,9 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
size = zram_get_obj_size(zram, index);
+ if (size != PAGE_SIZE)
+ 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);
@@ -1259,8 +1263,6 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
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);