| Message ID | 20160622125534.1267407-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c index 22af12f8b8eb..3ab4e2d1202c 100644 --- a/drivers/target/target_core_iblock.c +++ b/drivers/target/target_core_iblock.c @@ -201,9 +201,9 @@ static unsigned long long iblock_emulate_read_cap_with_block_size( struct block_device *bd, struct request_queue *q) { - unsigned long long blocks_long = (div_u64(i_size_read(bd->bd_inode), - bdev_logical_block_size(bd)) - 1); u32 block_size = bdev_logical_block_size(bd); + unsigned int block_shift = ilog2(block_size); + unsigned long long blocks_long = (i_size_read(bd->bd_inode) >> block_shift) - 1; if (block_size == dev->dev_attrib.block_size) return blocks_long;
Enabling CONFIG_UBSAN_SANITIZE_ALL on ARM caused a link error: drivers/target/built-in.o: In function `iblock_emulate_read_cap_with_block_size.constprop.1': target_core_iblock.c:(.text+0xc2774): undefined reference to `____ilog2_NaN' target_core_iblock.c:(.text+0xc27f8): undefined reference to `__aeabi_uldivmod' target_core_iblock.c:(.text+0xc299c): undefined reference to `__aeabi_uldivmod' This is caused by gcc not behaving in the expected ways with __builtin_constant_p(), but it also points to somewhat inefficient code: As we know that the block size is a power-of-two value, we can turn the expensive 64-bit division into a simpler variable bit shift. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/target/target_core_iblock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 2.9.0