This series introduces a proposal to implementing atomic writes in the kernel for torn-write protection. This series takes the approach of adding a new "atomic" flag to each of pwritev2() and iocb->ki_flags - RWF_ATOMIC and IOCB_ATOMIC, respectively. When set, these indicate that we want the write issued "atomically". Only direct IO is supported and for block devices and XFS. The atomic writes feature requires dedicated HW support, like SCSI WRITE_ATOMIC_16 command. man pages update has been posted at: https://lore.kernel.org/linux-api/20230929093717.2972367-1-john.g.garry@xxxxxxxxxx/T/#t The goal here is to provide an interface that allow applications use application-specific block sizes larger than logical block size reported by the storage device or larger than filesystem block size as reported by stat(). With this new interface, application blocks will never be torn or fractured when written. For a power fail, for each individual application block, all or none of the data to be written. A racing atomic write and read will mean that the read sees all the old data or all the new data, but never a mix of old and new. Two new fields are added to struct statx - atomic_write_unit_min and atomic_write_unit_max. For each atomic individual write, the total length of a write must be a between atomic_write_unit_min and atomic_write_unit_max, inclusive, and a power-of-2. The write must also be at a natural offset in the file wrt the write length. For XFS, we must ensure extent alignment with the userspace block size. XFS supports an extent size hint. However, it must be ensured that the hint is honoured. For this, a new flag is added - forcealign - to instruct the XFS block allocator to always honour the extent size hint. The user would typically set the extent size hint at the userspace block size to support atomic writes. The atomic_write_unit_{min, max} values from statx on an XFS file will consider both the backing bdev atomic_write_unit_{min, max} values and the extent alignment for the file. SCSI sd.c and scsi_debug and NVMe kernel support is added. xfsprogs update for forcealign is at: https://lore.kernel.org/linux-xfs/20230929095342.2976587-1-john.g.garry@xxxxxxxxxx/T/#t This series is based on v6.6-rc3. Major changes since RFC (https://lore.kernel.org/linux-scsi/20230503183821.1473305-1-john.g.garry@xxxxxxxxxx/): - Add XFS forcealign feature - Only allow writing a single userspace block Alan Adamson (1): nvme: Support atomic writes Darrick J. Wong (3): fs: xfs: Introduce FORCEALIGN inode flag fs: xfs: Make file data allocations observe the 'forcealign' flag fs: xfs: Enable file data forcealign feature Himanshu Madhani (2): block: Add atomic write operations to request_queue limits block: Add REQ_ATOMIC flag John Garry (13): block: Limit atomic writes according to bio and queue limits block: Pass blk_queue_get_max_sectors() a request pointer block: Limit atomic write IO size according to atomic_write_max_sectors block: Error an attempt to split an atomic write bio block: Add checks to merging of atomic writes block: Add fops atomic write support fs: xfs: Don't use low-space allocator for alignment > 1 fs: xfs: Support atomic write for statx fs: iomap: Atomic write support fs: xfs: iomap atomic write support scsi: sd: Support reading atomic properties from block limits VPD scsi: sd: Add WRITE_ATOMIC_16 support scsi: scsi_debug: Atomic write support Prasad Singamsetty (2): fs/bdev: Add atomic write support info to statx fs: Add RWF_ATOMIC and IOCB_ATOMIC flags for atomic write support Documentation/ABI/stable/sysfs-block | 42 ++ block/bdev.c | 33 +- block/blk-merge.c | 92 ++++- block/blk-mq.c | 2 +- block/blk-settings.c | 76 ++++ block/blk-sysfs.c | 33 ++ block/blk.h | 9 +- block/fops.c | 42 +- drivers/nvme/host/core.c | 29 ++ drivers/scsi/scsi_debug.c | 587 +++++++++++++++++++++------ drivers/scsi/scsi_trace.c | 22 + drivers/scsi/sd.c | 57 ++- drivers/scsi/sd.h | 7 + fs/iomap/direct-io.c | 26 +- fs/iomap/trace.h | 3 +- fs/stat.c | 15 +- fs/xfs/libxfs/xfs_bmap.c | 26 +- fs/xfs/libxfs/xfs_format.h | 9 +- fs/xfs/libxfs/xfs_inode_buf.c | 40 ++ fs/xfs/libxfs/xfs_inode_buf.h | 3 + fs/xfs/libxfs/xfs_sb.c | 3 + fs/xfs/xfs_inode.c | 12 + fs/xfs/xfs_inode.h | 5 + fs/xfs/xfs_ioctl.c | 18 + fs/xfs/xfs_iomap.c | 40 +- fs/xfs/xfs_iops.c | 51 +++ fs/xfs/xfs_iops.h | 4 + fs/xfs/xfs_mount.h | 2 + fs/xfs/xfs_super.c | 4 + include/linux/blk_types.h | 2 + include/linux/blkdev.h | 37 +- include/linux/fs.h | 1 + include/linux/iomap.h | 1 + include/linux/stat.h | 2 + include/scsi/scsi_proto.h | 1 + include/trace/events/scsi.h | 1 + include/uapi/linux/fs.h | 7 +- include/uapi/linux/stat.h | 7 +- 38 files changed, 1179 insertions(+), 172 deletions(-) -- 2.31.1
