[ adding linux-api to the cover letter for notification, will send the full set to linux-api for v3 ] On Thu, Aug 3, 2017 at 7:28 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > Changes since v1 [1]: > * Add IS_IOMAP_IMMUTABLE() checks to xfs ioctl paths that perform block > map changes (xfs_alloc_file_space and xfs_free_file_space) (Darrick) > > * Rather than complete a partial write, fail all writes that would > attempt to extend the file size (Darrick) > > * Introduce FALLOC_FL_UNSEAL_BLOCK_MAP as an explicit operation type for > clearing S_IOMAP_IMMUTABLE (Dave) > > * Rework xfs_seal_file_space() to first complete hole-fill and unshare > operations and then check the file for suitability under > XFS_ILOCK_EXCL. (Darrick) > > * Add an FS_XFLAG_IOMAP_IMMUTABLE flag so the immutable state can be > seen by xfs_io. (Dave) > > * Move the setting of S_IOMAP_IMMUTABLE to be atomic with respect to the > successful transaction that records XFS_DIFLAG2_IOMAP_IMMUTABLE. > (Darrick, Dave) > > * Switch to a 'goto out_unlock' style in xfs_seal_file_space() to > cleanup 'if / else' tree, and use the mapping_mapped() helper. (Dave) > > * Rely on XFS_MMAPLOCK_EXCL for reading a stable state of > mapping->i_mmap. (Dave) > > [1]: http://marc.info/?l=linux-fsdevel&m=150135785712967&w=2 > > --- > > The daxfile proposal a few weeks back [2] sought to piggy back on the > swapfile implementation to approximate a block map immutable file. This > is an idea Dave originated last year to solve the dax "flush from > userspace" problem [3]. > > The discussion yielded several results. First, Christoph pointed out > that swapfiles are subtly broken [4]. Second, Darrick [5] and Dave [6] > proposed how to properly implement a block map immutable file. Finally, > Dave identified some improvements to swapfiles that can be built on the > block-map-immutable mechanism. These patches seek to implement the first > part of the proposal and save the swapfile work to build on top once the > base mechanism is complete. > > While the initial motivation for this feature is support for > byte-addressable updates of persistent memory and managing cache > maintenance from userspace, the applications of the feature are broader. > In addition to being the start of a better swapfile mechanism it can > also support a DMA-to-storage use case. This use case enables > data-acquisition hardware to DMA directly to a storage device address > while being safe in the knowledge that storage mappings will not change. > > [2]: https://lkml.org/lkml/2017/6/16/790 > [3]: https://lkml.org/lkml/2016/9/11/159 > [4]: https://lkml.org/lkml/2017/6/18/31 > [5]: https://lkml.org/lkml/2017/6/20/49 > [6]: https://www.spinics.net/lists/linux-xfs/msg07871.html > > --- > > Dan Williams (5): > fs, xfs: introduce S_IOMAP_IMMUTABLE > fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP > fs, xfs: introduce FALLOC_FL_UNSEAL_BLOCK_MAP > xfs: introduce XFS_DIFLAG2_IOMAP_IMMUTABLE > xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in response to fallocate > > > fs/attr.c | 10 ++ > fs/open.c | 22 +++++ > fs/read_write.c | 3 + > fs/xfs/libxfs/xfs_format.h | 5 + > fs/xfs/xfs_bmap_util.c | 181 +++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/xfs_bmap_util.h | 5 + > fs/xfs/xfs_file.c | 16 +++- > fs/xfs/xfs_inode.c | 2 > fs/xfs/xfs_ioctl.c | 7 ++ > fs/xfs/xfs_iops.c | 8 +- > include/linux/falloc.h | 4 + > include/linux/fs.h | 2 > include/uapi/linux/falloc.h | 20 +++++ > include/uapi/linux/fs.h | 1 > mm/filemap.c | 5 + > 15 files changed, 282 insertions(+), 9 deletions(-)
