* [PATCH] partition/efi: use ilog2 to compute block size
@ 2016-06-22 12:58 Arnd Bergmann
0 siblings, 0 replies; only message in thread
From: Arnd Bergmann @ 2016-06-22 12:58 UTC (permalink / raw)
To: Davidlohr Bueso, Jens Axboe
Cc: Arnd Bergmann, linux-efi, linux-block, linux-kernel
Enabling CONFIG_UBSAN_SANITIZE_ALL on ARM caused a link error:
last_lba.part.0':
:(.text+0xc3440): undefined reference to `____ilog2_NaN'
:(.text+0xc3538): undefined reference to `__aeabi_uldivmod'
:(.text+0xc38e8): 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>
---
block/partitions/efi.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index bcd86e5cd546..7d83cf069574 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -147,10 +147,13 @@ efi_crc32(const void *buf, unsigned long len)
*/
static u64 last_lba(struct block_device *bdev)
{
+ unsigned int blocksize;
+
if (!bdev || !bdev->bd_inode)
return 0;
- return div_u64(bdev->bd_inode->i_size,
- bdev_logical_block_size(bdev)) - 1ULL;
+
+ blocksize = bdev_logical_block_size(bdev);
+ return (bdev->bd_inode->i_size >> ilog2(blocksize)) - 1ULL;
}
static inline int pmbr_part_valid(gpt_mbr_record *part)
--
2.9.0
^ permalink raw reply related [flat|nested] only message in thread
only message in thread, other threads:[~2016-06-22 12:58 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-06-22 12:58 [PATCH] partition/efi: use ilog2 to compute block size Arnd Bergmann
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).