On Wed, Nov 28, 2012 at 10:16:21PM -0800, Linus Torvalds wrote: > On Wed, Nov 28, 2012 at 6:58 PM, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > But the fact that the code wants to do things like > > > > block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); > > > > seriously seems to be the main thing that keeps us using > > 'inode->i_blkbits'. Calculating bbits from bh->b_size is just costly > > enough to hurt (not everywhere, but on some machines). > > > > Very annoying. > > Hmm. Here's a patch that does that anyway. I'm not 100% happy with the > whole ilog2 thing, but at the same time, in other cases it actually > seems to improve code generation (ie gets rid of the whole unnecessary > two dereferences through page->mapping->host just to get the block > size, when we have it in the buffer-head that we have to touch > *anyway*). > > Comments? Again, untested. > > And I notice that Al Viro hasn't been cc'd, which is sad, since he's > been involved in much of fs/block_dev.c. > > Al - this is an independent patch to fs/buffer.c to make > fs/block_dev.c able to change the block size of a block device while > there is IO in progress that may still use the old block size. The > discussion has been on fsdevel and lkml, but you may have missed it... Umm... set_blocksize() is calling kill_bdev(), which does truncate_inode_pages(mapping, 0). What's going to happen to data in the dirty pages? IO in progress is not the only thing to worry about... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
