[0/9,v7] btrfs direct-io using iomap

Message

Goldwyn Rodrigues March 26, 2020, 9:02 p.m. UTC

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 v5.6-rc7. I have tested it against
xfstests.

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
- Removed lockdep_assert_held() near callers

Changes since v6
- Fixed hangs due to underlying device failures
- Removed the patch to wait while releasing pages

 fs/btrfs/btrfs_inode.h |   18 --
 fs/btrfs/ctree.h       |    4
 fs/btrfs/file.c        |  124 +++++++++++++-
 fs/btrfs/inode.c       |  418 +++++++++++++++----------------------------------
 fs/direct-io.c         |   19 --
 fs/iomap/direct-io.c   |   17 +
 include/linux/fs.h     |    4
 include/linux/iomap.h  |    2
 mm/filemap.c           |   13 -
 9 files changed, 274 insertions(+), 345 deletions(-)

Comments

David Sterba March 27, 2020, 3:56 p.m. UTC | #1

On Thu, Mar 26, 2020 at 04:02:45PM -0500, Goldwyn Rodrigues wrote:
> Changes since v6
> - Fixed hangs due to underlying device failures
> - Removed the patch to wait while releasing pages

There were no hangs and all tests finished, but there were some failures
that seem to be caused by the patchset. I'll send you the logs.