Superblock (and its copies) is the only data structure in btrfs which has a
fixed location on a device. Since we cannot overwrite in a sequential write
required zone, we cannot place superblock in the zone. One easy solution
is limiting superblock and copies to be placed only in conventional zones.
However, this method has two downsides: one is reduced number of superblock
copies. The location of the second copy of superblock is 256GB, which is in
a sequential write required zone on typical devices in the market today.
So, the number of superblock and copies is limited to be two. Second
downside is that we cannot support devices which have no conventional zones
at all.
To solve these two problems, we employ superblock log writing. It uses two
adjacent zones as a circular buffer to write updated superblocks. Once the
first zone is filled up, start writing into the second one. Then, when
both zones are filled up and before starting to write to the first zone
again, reset the first zone.
We can determine the position of the latest superblock by reading write
pointer information from a device. One corner case is when both zones are
full. For this situation, we read out the last superblock of each zone, and
compare them to determine which zone is older.
The following zones are reserved as the circular buffer on ZONED btrfs.
- primary superblock: offset 0B (and the following zone)
- first copy: offset 512G (and the following zone)
- Second copy: offset 4T (4096G, and the following zone)
If these reserved zones are conventional, superblock is written fixed at
the start of the zone without logging.
Currently, superblock reading/writing is done by pread/pwrite. This
commit replace the call sites with sbread/sbwrite to wrap the functions.
For zoned btrfs, btrfs_sb_io which is called from sbread/sbwrite
reverses the IO position back to a mirror number, maps the mirror number
into the superblock logging position, and do the IO.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
dump_superblock() is useful to debug eg. btrfs-image errors, like
fsck/012-* test case, where the superblock itself has something wrong
from the original image.
Export it so that we can call it in gdb.
Since we're exporting dump_superblock(), rename it to
btrfs_print_superblock() to following the existing naming schema.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Add definition, crypto wrappers and support to mkfs for blake2 for
checksumming. There are 2 aliases either blake2 or blake2b.
Signed-off-by: David Sterba <dsterba@suse.com>
Add the definition to the checksum types and let mkfs accept it.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
With the introduction of xxhash64 to btrfs-progs we created a crypto/
directory for all the hashes used in btrfs (although no
cryptographically secure hash is there yet).
Move the crc32c implementation from kernel-lib/ to crypto/ as well so we
have all hashes consolidated.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Adding this table will make extending btrfs-progs with new checksum types
easier.
Also add accessor functions to access the table fields.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Add a helper to check if we have a valid csum type from the super block.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Update the checksumming API to be able to cope with more checksum types
than just CRC32C. The finalization call is merged into btrfs_csum_data.
There are some fixme's and asserts added that need to be resolved.
Co-developed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
In preparation to supporting new checksum algorithm pass the checksum type
to btrfs_csum_data/btrfs_csum_final, this allows us to encapsulate any
differences in processing into the respective functions
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Pass pointer to a generic buffer instead of fixed size that crc32c
currently uses.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
For options that do not have the long description, the empty string is
required to mark where the options start. Some commands were missing
that.
Signed-off-by: David Sterba <dsterba@suse.com>
