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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>
This commit is contained in:
Peter Zijlstra 2020-10-19 12:13:53 +02:00 committed by Jens Axboe
parent db07327270
commit 0669d2b265
1 changed files with 5 additions and 3 deletions
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8
drivers/block/zram/zram_drv.c
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@ -1218,10 +1218,11 @@ out:
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);