Commit 30321c7b authored May 05, 2014 by David Miller Committed by Linus Torvalds May 05, 2014

slab: Fix off by one in object max number tests.



If freelist_idx_t is a byte, SLAB_OBJ_MAX_NUM should be 255 not 256, and
likewise if freelist_idx_t is a short, then it should be 65535 not
65536.

This was leading to all kinds of random crashes on sparc64 where
PAGE_SIZE is 8192.  One problem shown was that if spinlock debugging was
enabled, we'd get deadlocks in copy_pte_range() or do_wp_page() with the
same cpu already holding a lock it shouldn't hold, or the lock belonging
to a completely unrelated process.

Fixes: a41adfaa ("slab: introduce byte sized index for the freelist of a slab")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 7cc68973

mm/slab.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -166,7 +166,7 @@ typedef unsigned char freelist_idx_t;
		typedef unsigned short freelist_idx_t;
		#endif

		#define SLAB_OBJ_MAX_NUM (1 << sizeof(freelist_idx_t) * BITS_PER_BYTE)
		#define SLAB_OBJ_MAX_NUM ((1 << sizeof(freelist_idx_t) * BITS_PER_BYTE) - 1)

		/*
		* true if a page was allocated from pfmemalloc reserves for network-based

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