On Mon, Dec 02, 2013 at 08:12:20PM +0100, Helge Deller wrote: > Compiling a 32bit kernel with CONFIG_LBDAF=n gives this compiler warning: > /drivers/md/md.c: In function ‘super_90_load’: > /drivers/md/md.c:1068:3: warning: large integer implicitly truncated to unsigned type [-Woverflow] > > Fix it by casting the calculated value to a sector_t type. > > Signed-off-by: Helge Deller <deller@xxxxxx> > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index e60cebf..b56f1c7 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -1065,7 +1065,7 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor > * record this size) > */ > if (rdev->sectors >= (2ULL << 32) && sb->level >= 1) > - rdev->sectors = (2ULL << 32) - 2; > + rdev->sectors = (sector_t) ((2ULL << 32) - 2); > > if (rdev->sectors < ((sector_t)sb->size) * 2 && sb->level >= 1) > /* "this cannot possibly happen" ... */ > @@ -1356,7 +1356,7 @@ super_90_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors) > * 4TB == 2^32 KB, or 2*2^32 sectors. > */ > if (num_sectors >= (2ULL << 32) && rdev->mddev->level >= 1) > - num_sectors = (2ULL << 32) - 2; > + num_sectors = (sector_t) ((2ULL << 32) - 2); > md_super_write(rdev->mddev, rdev, rdev->sb_start, rdev->sb_size, > rdev->sb_page); > md_super_wait(rdev->mddev); > It does overflow and get truncated on 32-bit systems without LABDF. Casting is just hiding the problem! 32-bit systems without LABDF do not support block devices larger than 2TB, and thus, should not worry about larger than 4TB devices. This code should either be ifdef'd to 64-bit or LABDF, or should test for the size of sector_t. The second option would still need some change in the code in order to avoid the warning, or we should don't care about them, since testing for num_sectors >= (2ULL << 32) should always be false. Regards. Cascardo. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
