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
