Messages in this thread |  | | | Date | Sat, 4 Jul 2009 14:29:40 -0400 | | From | "Doug Graham" <> | | Subject | More fun with MinixFS V3 |
I was just looking over an old thread about MinixFs V3 support and starting to get worried that my tweaks to support blocksizes of 512 bytes (for a small filesystem with many small files) might be broken. This is the thread here: http://lkml.org/lkml/2006/5/6/50. The nblocks() routine in fs/minix/itree_common.c now looks like this:
static inline unsigned nblocks(loff_t size, struct super_block *sb) { int k = sb->s_blocksize_bits - 10; unsigned blocks, res, direct = DIRECT, i = DEPTH; blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k); ... and what had be worred at first is that sb->s_blocksize_bits will be 9 with a blocksize of 512, which makes k negative. But all may not be lost, since k is only used once after this, after adding BLOCK_SIZE_BITS (10) to it. At least that makes it nonnegative again, but then the question is: what exactly is being accomplished here? First we subtract 10, then add it back? The result is effectively this:
blocks = (size + sb->s_blocksize - 1) >> sb->s_blocksize_bits
which looks entirely correct to me. Is there any reason the code couldn't just be written this way to begin with?
--Doug
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