[PATCH] zram: Fix __zram_bvec_{read,write}() locking order
From: Peter Zijlstra <peterz@infradead.org>
Date: 2020-10-19 10:14:04
Also in:
lkml
Subsystem:
block layer, the rest, zram compressed ram block device drvier · Maintainers:
Jens Axboe, Linus Torvalds, Minchan Kim, Sergey Senozhatsky
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 <redacted> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Mikhail Gavrilov <redacted> --- drivers/block/zram/zram_drv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 9100ac36670a..c1e2c2e1cde8 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c@@ -1216,10 +1216,11 @@ 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)) {
@@ -1250,6 +1251,9 @@ 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);
@@ -1257,8 +1261,6 @@ 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);