On Mon, Jul 16 2012 at 2:35pm -0400, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > dm-thin: fix discard_granularity > > The kernel expects that limits->discard_granularity is a power of two. > Set this limit only if we use a power of two block size. > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > --- > drivers/md/dm-thin.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > Index: linux-3.5-rc6-fast/drivers/md/dm-thin.c > =================================================================== > --- linux-3.5-rc6-fast.orig/drivers/md/dm-thin.c 2012-07-16 20:07:49.000000000 +0200 > +++ linux-3.5-rc6-fast/drivers/md/dm-thin.c 2012-07-16 20:08:01.000000000 +0200 > @@ -2502,7 +2502,8 @@ static void set_discard_limits(struct po > * bios cover a block partially. A discard that spans a block boundary > * is not sent to this target. > */ > - limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; > + if (pool->sectors_per_block_shift >= 0) > + limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; > limits->discard_zeroes_data = pool->pf.zero_new_blocks; > } Given the block layer's assumption that discard_granularity is always a power of 2: thinp should disable discard if the thinp blocksize is a non power of 2. So this patch isn't correct (discard support should be disabled in pool_ctr based on the specified blocksize). Future work should be: 1) explore/eliminate the block layer's power of 2 constraints 2) divorce thinp's discard limits (for discard passdown) from the pool's blocksize -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
