zram: Fix __zram_bvec_{read,write}() locking order (0669d2b2) · Commits · 戴 / test

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>

drivers/block/zram/zram_drv.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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);

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