The high keys in a rmapbt node block aren't naturally aligned. xchk_rmapbt_check_unwritten_in_keyflags() reads rm_offset through union xfs_btree_key and the union is 8-byte aligned. The compiler may use an 8-byte load, and on sparc64 each high key takes an unaligned access trap: Kernel unaligned access at TPC[105a54d8] xchk_rmapbt_check_unwritten_in_keyflags+0xb8/0x160 [xfs] Read the keys through the packed struct xfs_rmap_key instead. This tells the compiler they may be unaligned. Decode rm_offset with be64_to_cpu() and drop the byte-swapped flag. Fixes: 38384569a2a8 ("xfs: detect unwritten bit set in rmapbt node block keys") Reported-by: Jan Engelhardt Closes: https://github.com/sparclinux/issues/issues/115 Suggested-by: Dave Chinner Cc: stable@vger.kernel.org # v6.4+ Signed-off-by: Stian Halseth --- Tested on sparc64 (T4, 7.3.4) by scrubbing the rmapbt of a loop-mounted image: alignment faults per scrub went from about 4000 to 0. v3: separate key and rkey variables plus a comment (Dave), shorter changelog. v2: https://lore.kernel.org/all/20261110223927.558557-1-stian@itx.no/ v1: https://lore.kernel.org/all/20261109134853.1659991-1-stian@itx.no/ fs/xfs/scrub/rmap.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/fs/xfs/scrub/rmap.c b/fs/xfs/scrub/rmap.c index 68e2847c962bb..7609c03cdc8ab 100644 --- a/fs/xfs/scrub/rmap.c +++ b/fs/xfs/scrub/rmap.c @@ -149,8 +149,6 @@ xchk_rmapbt_check_unwritten_in_keyflags( struct xfs_scrub *sc = bs->sc; struct xfs_btree_cur *cur = bs->cur; struct xfs_btree_block *keyblock; - union xfs_btree_key *lkey, *hkey; - __be64 badflag = cpu_to_be64(XFS_RMAP_OFF_UNWRITTEN); unsigned int level; if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_PREEN) @@ -159,6 +157,14 @@ xchk_rmapbt_check_unwritten_in_keyflags( for (level = 1; level < cur->bc_nlevels; level++) { struct xfs_buf *bp; unsigned int ptr; + /* + * The on-disk high keys in an rmap node block are not + * naturally aligned, so decode them through the packed + * struct xfs_rmap_key to make the compiler treat them as + * unaligned. + */ + union xfs_btree_key *key; + const struct xfs_rmap_key *rkey; /* Only check the first time we've seen this node block. */ if (cur->bc_levels[level].ptr > 1) @@ -166,15 +172,16 @@ xchk_rmapbt_check_unwritten_in_keyflags( keyblock = xfs_btree_get_block(cur, level, &bp); for (ptr = 1; ptr <= be16_to_cpu(keyblock->bb_numrecs); ptr++) { - lkey = xfs_btree_key_addr(cur, ptr, keyblock); - - if (lkey->rmap.rm_offset & badflag) { + key = xfs_btree_key_addr(cur, ptr, keyblock); + rkey = &key->rmap; + if (be64_to_cpu(rkey->rm_offset) & XFS_RMAP_OFF_UNWRITTEN) { xchk_btree_set_preen(sc, cur, level); break; } - hkey = xfs_btree_high_key_addr(cur, ptr, keyblock); - if (hkey->rmap.rm_offset & badflag) { + key = xfs_btree_high_key_addr(cur, ptr, keyblock); + rkey = &key->rmap; + if (be64_to_cpu(rkey->rm_offset) & XFS_RMAP_OFF_UNWRITTEN) { xchk_btree_set_preen(sc, cur, level); break; } -- 2.43.0