On 2:01 16/12, Nikolay Borisov wrote: > > > On 13.12.19 г. 21:57 ч., Goldwyn Rodrigues wrote: > > This is an effort to use iomap for direct I/O in btrfs. This would > > change the call from __blockdev_direct_io() to iomap_dio_rw(). > > > > The main objective is to lose the buffer head and use bio defined by > > iomap code, and hopefully to use more of generic-FS codebase. > > > > These patches are based and tested on v5.5-rc1. I have tested it against > > xfstests/btrfs. > > > > The tree is available at > > https://github.com/goldwynr/linux/tree/btrfs-iomap-dio > > > > Changes since v1 > > - Incorporated back the efficiency change for inode locking > > - Review comments about coding style and git comments > > - Merge related patches into one > > - Direct read to go through btrfs_direct_IO() > > - Removal of no longer used function dio_end_io() > > > > Changes since v2 > > - aligning iomap offset/length to the position/length of I/O > > - Removed btrfs_dio_data > > - Removed BTRFS_INODE_READDIO_NEED_LOCK > > - Re-incorporating write efficiency changes caused lockdep_assert() in > > iomap to be triggered, remove that code. > > > > Changes since v3 > > - Fixed freeze on generic/095. Use iomap_end() to account for > > failed/incomplete dio instead of btrfs_dio_data > > > > Changes since v4 > > - moved lockdep_assert_held() to functions calling iomap_dio_rw() > > This may be called immidiately after calling inode lock and > > may feel not required, but it seems important. > > - Removed comments which are no longer required > > - Changed commit comments to make them more appropriate > > > > Changes since v5 > > - restore inode_dio_wait() in truncate > > I'm confused about this - you no longer call inode_dio_begin after patch > 4/8 so inode_dio_wait which is left intact in truncate can never trigger > a wait really. Exclusion is provided by the fact that btrfs_direct_IO is > called with rwsem held shared and truncate holds it exclusive? So what > necessitated restoring inode_dio_wait? The optimization of the write path of direct I/O. The rwsem is released if write is within i_size. This is also the reason we removed lockdep_assert_held(). Reference: 38851cc19adb ("Btrfs: implement unlocked dio write") This was inspired by ext4. However, ext4 after it's switch to iomap_dio_rw() does not employ this optimization. > > > Another point, I don't see whether you have explicitly addressed > concerns raised in: > > https://lore.kernel.org/linux-btrfs/20191212003043.31093-1-rgoldwyn@xxxxxxx/T/#me7f96506e5a1d921d05b76d01ecf6ea1ebcea594 I did address it by releasing csums (referring io_bio) before calling bio_endio(). -- Goldwyn
