As mentioned elsewhere in dm-integrity.txt, creating a new integrity device requires creating a small integrity device on top of the base device that formats the base device, reading the provided data sectors out of the superblock, and then recreating the integrity device with the correct size. For this, userspace must know the offset, length, and endianness of the provided_data_sectors field in the superblock. Document all fields mentioned in the txt to include this, based on struct superblock in dm-integrity.c. Extra fields in struct superblock not already mentioned in the txt remain undocumented. Signed-off-by: Andy Grover <agrover@xxxxxxxxxx> --- Documentation/device-mapper/dm-integrity.txt | 26 ++++++++++++-------- 1 file changed, 16 insertions(+), 10 deletions(-) diff --git a/Documentation/device-mapper/dm-integrity.txt b/Documentation/device-mapper/dm-integrity.txt index 297251b0d2d5..3d28328f16c1 100644 --- a/Documentation/device-mapper/dm-integrity.txt +++ b/Documentation/device-mapper/dm-integrity.txt @@ -158,16 +158,22 @@ The layout of the formatted block device: storing LUKS metadata or for other purpose), the size of the reserved area is specified in the target arguments * superblock (4kiB) - * magic string - identifies that the device was formatted - * version - * log2(interleave sectors) - * integrity tag size - * the number of journal sections - * provided data sectors - the number of sectors that this target - provides (i.e. the size of the device minus the size of all - metadata and padding). The user of this target should not send - bios that access data beyond the "provided data sectors" limit. - * flags - a flag is set if journal_mac is used + +offset and length in bytes. All values little-endian. + +offset length description +0 8 magic string - identifies that the device was formatted +8 1 version +9 1 log2(interleave sectors) +10 2 integrity tag size +12 4 the number of journal sections +16 8 provided data sectors - the number of sectors that this + target provides (i.e. the size of the device minus the size of + all metadata and padding). The user of this target should not + send bios that access data beyond the "provided data sectors" + limit. +24 4 flags - a flag is set if journal_mac is used + * journal The journal is divided into sections, each section contains: * metadata area (4kiB), it contains journal entries -- 2.17.2 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
