[PATCHSET,v24.0,0/5] xfs: online repair of extended attributes

Message

Darrick J. Wong Dec. 30, 2022, 10:14 p.m. UTC

Hi all,

This series employs atomic extent swapping to enable safe reconstruction
of extended attribute data attached to a file.  Because xattrs do not
have any redundant information to draw off of, we can at best salvage
as much data as we can and build a new structure.

Rebuilding an extended attribute structure consists of these three
steps:

First, we walk the existing attributes to salvage as many of them as we
can, by adding them as new attributes attached to the repair tempfile.
We need to add a new xfile-based data structure to hold blobs of
arbitrary length to stage the xattr names and values.

Second, we write the salvaged attributes to a temporary file, and use
atomic extent swaps to exchange the entire attribute fork between the
two files.

Finally, we reap the old xattr blocks (which are now in the temporary
file) as carefully as we can.

If you're going to start using this mess, you probably ought to just
pull from my git trees, which are linked below.

This is an extraordinary way to destroy everything.  Enjoy!
Comments and questions are, as always, welcome.

--D

kernel git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-xattrs

xfsprogs git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=repair-xattrs

fstests git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=repair-xattrs
---
 fs/xfs/Makefile               |    2 
 fs/xfs/libxfs/xfs_attr.c      |    2 
 fs/xfs/libxfs/xfs_attr.h      |    2 
 fs/xfs/libxfs/xfs_da_format.h |    5 
 fs/xfs/libxfs/xfs_swapext.c   |    2 
 fs/xfs/libxfs/xfs_swapext.h   |    1 
 fs/xfs/scrub/attr.c           |   33 +
 fs/xfs/scrub/attr.h           |    7 
 fs/xfs/scrub/attr_repair.c    | 1158 +++++++++++++++++++++++++++++++++++++++++
 fs/xfs/scrub/dabtree.c        |   16 +
 fs/xfs/scrub/dabtree.h        |    3 
 fs/xfs/scrub/repair.c         |   45 ++
 fs/xfs/scrub/repair.h         |    8 
 fs/xfs/scrub/scrub.c          |    2 
 fs/xfs/scrub/tempfile.c       |  176 ++++++
 fs/xfs/scrub/tempfile.h       |    2 
 fs/xfs/scrub/tempswap.h       |    2 
 fs/xfs/scrub/trace.h          |  106 ++++
 fs/xfs/scrub/xfarray.c        |   24 +
 fs/xfs/scrub/xfarray.h        |    2 
 fs/xfs/scrub/xfblob.c         |  176 ++++++
 fs/xfs/scrub/xfblob.h         |   27 +
 fs/xfs/xfs_buf.c              |    3 
 fs/xfs/xfs_trace.h            |    2 
 24 files changed, 1801 insertions(+), 5 deletions(-)
 create mode 100644 fs/xfs/scrub/attr_repair.c
 create mode 100644 fs/xfs/scrub/xfblob.c
 create mode 100644 fs/xfs/scrub/xfblob.h