Eryu Guan <guaneryu@xxxxxxxxx> writes: > On Fri, May 06, 2016 at 10:13:39AM -0400, Jeff Moyer wrote: >> Eryu Guan <guaneryu@xxxxxxxxx> writes: >> >> > On Thu, May 05, 2016 at 03:39:29PM -0400, Jeff Moyer wrote: >> >> I think this code operates on blocks for a reason: we're trying to >> >> determine if we'll trigger block allocation, right? For example, >> >> consider a sparse file with i_size of 2k, and a write to offset 2k into >> >> the file, with a file system block size of 4k. Should that have create >> >> set or not? >> > >> > Thanks for pointing this out! I think 'create' should be 0 in this case, >> > my test failed in this case, with both 4.6-rc6 stock kernel and my >> > patched kernel. >> > >> > I'm testing an updated patch now, hopefully it's doing the right thing. >> > It's basiclly something like: >> > >> > if (offset < i_size) >> > create = 0; >> > else if ((block_in_file >> blkfactor) == (i_size >> (blkbits + blkfactor)) && >> > (i_size & ((1 << (blkbits + blkfactor)) - 1))) >> > create = 0; >> >> I think that can be simplified to a single check; something like: >> >> if (block_in_file < total_blocks_in_file) >> create = 0; > > I may miss something, but this doesn't seem right to me. Still take your > example, on a 4k block size & 512 sector size filesystem ... where blocks are in file system block size units. So: if (fs_block_in_file < total_fs_blocks_in_file) > Thanks very much! I'll split it to two patches, first one is a cleanup, > has no function change, second one is the real fix. This should make the > review easier. Typically the mininmal fix goes first (for ease of backporting to stable), and then the cleanup. As I said, though, this isn't critical, I'll take a look. Thanks! Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
