On Wed, Apr 18, 2019 at 09:27:11AM +0800, Shiyang Ruan wrote: > In XFS (under fsdax mode), reflink did not work correctly because xfs > iomap operators did not handle the inode with both reflink and dax flag. > > This patchset aims to take care of this issue to make COW operation work > correctly in XFS. > > XFS uses iomap to do read/write/mmap operations: > vfs interface xfs: > iomap_bengin(); --> xfs_iomap_begin(); > actor(); --> dax_iomap_actor() / mmap actor function > iomap_end(); --> xfs_iomap_end(); > > In xfs_iomap_begin(), COW operation is detected but not told to actor > function. To resolve this, a new field 'src_addr' is added into > 'struct iomap' to pass this COW info. It means the start address of > source blocks in a COW operation, for actor functions to copy data > before writing. > > In actor functions, the value of iomap->src_addr determines if it is a > COW operation. If it is, copy data from source blocks to destination > blocks first, and then write user data. > > After the COW operation, it is supposed to update the metadata of the > inode. Added in xfs_iomap_end(). How do the fs/iomap.c changes in your series compare with Goldwyn's "btrfs dax support" series that he put out today? Also, there are a few things missing: 1. A DAX-compatible file contents comparison function for the dedupe ioctl. 2. Checks that we aren't trying to reflink or dedupe between S_DAX and !S_DAX files. 3. Do we need to make changes to the hairy xfs_iolock_two_inodes_and_break_layout function to handle DAX? Seeing as it doesn't call xfs_break_dax_layouts... --D > > > Shiyang Ruan (4): > fs/iomap: Introduce src_addr for COW in fsdax mode. > fs/xfs: iomap: add handle for reflink in fsdax mode > fs/dax: copy source blocks before writing when COW > fs/xfs: iomap: update the extent list after a COW > > fs/dax.c | 70 +++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/xfs_iomap.c | 23 +++++++++++--- > include/linux/iomap.h | 4 +++ > 3 files changed, 93 insertions(+), 4 deletions(-) > > -- > 2.17.0 > > >
