On Wed, Apr 22, 2020 at 2:58 PM Marek Behun <marek.behun@xxxxxx> wrote: > > On Wed, 22 Apr 2020 14:44:46 -0600 > Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote: > > > e.g. from a 10m file created with truncate on two Btrfs file systems > > > > original holes format (default) > > > > item 6 key (257 EXTENT_DATA 0) itemoff 15768 itemsize 53 > > generation 7412 type 1 (regular) > > extent data disk byte 0 nr 0 > > extent data offset 0 nr 10485760 ram 10485760 > > extent compression 0 (none) > > > > On a file system with no-holes feature set, this item simply doesn't > > exist. I think basically it works by inference. Both kinds of files > > have size in the INODE_ITEM, e.g. > > > > item 4 key (257 INODE_ITEM 0) itemoff 32245 itemsize 160 > > generation 889509 transid 889509 size 10485760 nbytes 0 > > > > Sparse extents are explicitly stated in the original format with disk > > byte 0 in an EXTENT_DATA item; whereas in the newer format, sparse > > extents exist whenever EXTENT_DATA items don't completely describe the > > file's size. > > Ok this means that U-Boot currently gained support for the original > sparse extents. > > I fear that current u-boot does not handle the new no-holes feature. I'd advise it should support it, I think it's expected to become the default. But I don't know the time frame for that. Also, when the no-holes feature flag is not set, you can be certain only the original hole type is used. But when no-holes feature is set, it's possible for both types of holes to exist, because no-holes can be set after mkfs time by btrfstune. -- Chris Murphy
