On 6:42 21/12, Christoph Hellwig wrote: > So Ilooked into the "unlocked" direct I/O case, and I think the current > code using dio_sem is really sketchy. What btrfs really needs to do is > take i_rwsem shared by default for direct writes, and only upgrade to > the exclusive lock when needed, similar to xfs and the WIP ext4 code. > > While looking for that I also noticed two other things: > > - check_direct_IO looks pretty bogus > - btrfs_direct_IO really should be split and folded into the two > callers > > Untested patches attached. The first should probably go into a prep > patch, and the second could be folded into this one. Testing revealed that removing check_direct_IO will not work. We try and reserve space as a whole for the entire direct write. These checks safeguard from requests unaligned to fs_info->sectorsize. I liked the patch to split and fold the direct_IO code. However to merge it into this will make it difficult to understand the changes since we are moving it to a different file rather than changing in-place. A separate patch would better serve as a cleanup. -- Goldwyn
