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To enable DAX to do atomic allocation of zeroed extents, we need to drive the block zeroing deep into the allocator. Because xfs_bmapi_write() can return merged extents on allocation that were only partially allocated (i.e. requested range spans allocated and hole regions, allocation into the hole was contiguous), we cannot zero the extent returned from xfs_bmapi_write() as that can overwrite existing data with zeros. Hence we have to drive the extent zeroing into the allocation code, prior to where we merge the extents into the BMBT and return the resultant map. This means we need to propagate this need down to the xfs_alloc_vextent() and issue the block zeroing at this point. While this functionality is being introduced for DAX, there is no reason why it is specific to DAX - we can per-zero blocks during the allocation transaction on any type of device. It's just slow (and usually slower than unwritten allocation and conversion) on traditional block devices so doesn't tend to get used. We can, however, hook hardware zeroing optimisations via sb_issue_zeroout() to this operation, so it may be useful in future and hence the "allocate zeroed blocks" API needs to be implementation neutral. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com> |
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| .. | ||
| xfs_alloc_btree.c | ||
| xfs_alloc_btree.h | ||
| xfs_alloc.c | ||
| xfs_alloc.h | ||
| xfs_attr_leaf.c | ||
| xfs_attr_leaf.h | ||
| xfs_attr_remote.c | ||
| xfs_attr_remote.h | ||
| xfs_attr_sf.h | ||
| xfs_attr.c | ||
| xfs_bit.c | ||
| xfs_bit.h | ||
| xfs_bmap_btree.c | ||
| xfs_bmap_btree.h | ||
| xfs_bmap.c | ||
| xfs_bmap.h | ||
| xfs_btree.c | ||
| xfs_btree.h | ||
| xfs_cksum.h | ||
| xfs_da_btree.c | ||
| xfs_da_btree.h | ||
| xfs_da_format.c | ||
| xfs_da_format.h | ||
| xfs_dir2_block.c | ||
| xfs_dir2_data.c | ||
| xfs_dir2_leaf.c | ||
| xfs_dir2_node.c | ||
| xfs_dir2_priv.h | ||
| xfs_dir2_sf.c | ||
| xfs_dir2.c | ||
| xfs_dir2.h | ||
| xfs_dquot_buf.c | ||
| xfs_format.h | ||
| xfs_fs.h | ||
| xfs_ialloc_btree.c | ||
| xfs_ialloc_btree.h | ||
| xfs_ialloc.c | ||
| xfs_ialloc.h | ||
| xfs_inode_buf.c | ||
| xfs_inode_buf.h | ||
| xfs_inode_fork.c | ||
| xfs_inode_fork.h | ||
| xfs_log_format.h | ||
| xfs_log_recover.h | ||
| xfs_log_rlimit.c | ||
| xfs_quota_defs.h | ||
| xfs_rtbitmap.c | ||
| xfs_sb.c | ||
| xfs_sb.h | ||
| xfs_shared.h | ||
| xfs_symlink_remote.c | ||
| xfs_trans_resv.c | ||
| xfs_trans_resv.h | ||
| xfs_trans_space.h | ||
| xfs_types.h | ||