[PATCH 0/4] xfsprogs: Extend per-inode extent counters

[Chandan Babu R <chandanrlinux@gmail.com>]

The kernel commit xfs: fix inode fork extent count overflow
(3f8a4f1d876d3e3e49e50b0396eaffcc4ba71b08) mentions that 10 billion
data fork extents should be possible to create. However the
corresponding on-disk field has a signed 32-bit type. Hence this
patchset extends the per-inode data extent counter to 47 bits. The
length of 47-bits was chosen because,
Maximum file size = 2^63.
Maximum extent count when using 64k block size = 2^63 / 2^16 = 2^47.

Also, XFS has a per-inode xattr extent counter which is 16 bits
wide. A workload which
1. Creates 1 million 255-byte sized xattrs,
2. Deletes 50% of these xattrs in an alternating manner,
3. Tries to insert 400,000 new 255-byte sized xattrs
   causes the xattr extent counter to overflow.

Dave tells me that there are instances where a single file has more
than 100 million hardlinks. With parent pointers being stored in
xattrs, we will overflow the signed 16-bits wide xattr extent counter
when large number of hardlinks are created. Hence this patchset
extends the on-disk field to 32-bits.

The following changes are made to accomplish this,
1. A new incompat superblock flag to prevent older kernels from mounting
   the filesystem. This flag has to be set during mkfs time.
2. Carve out a new 32-bit field from xfs_dinode->di_pad2[]. This field
   holds the most significant 15 bits of the data extent counter.
3. Carve out a new 16-bit field from xfs_dinode->di_pad2[]. This field
   holds the most significant 16 bits of the attr extent counter.

This patchset can also be obtained from
https://github.com/chandanr/xfsprogs-dev.git at branch
xfs-incompat-extend-extcnt-v1.

Chandan Babu R (4):
  xfsprogs: Introduce xfs_iext_max() helper
  xfsprogs: Introduce xfs_dfork_nextents() helper
  xfsprogs: Extend data/attr fork extent counter width
  xfsprogs: Add wideextcnt mkfs option

 db/bmap.c                  |  8 +--
 db/btdump.c                |  4 +-
 db/check.c                 |  2 +-
 db/field.c                 |  4 --
 db/field.h                 |  2 -
 db/frag.c                  |  8 +--
 db/inode.c                 | 31 +++++++++---
 db/metadump.c              |  4 +-
 include/libxlog.h          |  6 ++-
 libxfs/xfs_bmap.c          | 21 ++++----
 libxfs/xfs_format.h        | 24 +++++----
 libxfs/xfs_inode_buf.c     | 78 +++++++++++++++++++++++-------
 libxfs/xfs_inode_buf.h     |  6 ++-
 libxfs/xfs_inode_fork.c    |  7 +--
 libxfs/xfs_inode_fork.h    | 17 +++++++
 libxfs/xfs_log_format.h    |  8 +--
 libxfs/xfs_types.h         |  6 ++-
 logprint/log_misc.c        | 21 ++++++--
 logprint/log_print_all.c   | 30 +++++++++---
 logprint/log_print_trans.c |  2 +-
 man/man8/mkfs.xfs.8        |  7 +++
 mkfs/xfs_mkfs.c            | 23 +++++++++
 repair/attr_repair.c       |  2 +-
 repair/dinode.c            | 99 ++++++++++++++++++++++----------------
 repair/prefetch.c          |  2 +-
 25 files changed, 292 insertions(+), 130 deletions(-)

-- 
2.28.0