[PATCH 6.6 266/396] xfs: fix an off-by-one error in xreap_agextent_binval

Greg Kroah-Hartman
2024-04-01T16:49:26Z

commit c0e37f07d2bd3c1ee3fb5a650da7d8673557ed16 upstream.

Overall, this function tries to find and invalidate all buffers for a
given extent of space on the data device. The inner for loop in this
function tries to find all xfs_bufs for a given daddr. The lengths of
all possible cached buffers range from 1 fsblock to the largest needed
to contain a 64k xattr value (~17fsb). The scan is capped to avoid
looking at anything buffer going past the given extent.

Unfortunately, the loop continuation test is wrong -- max_fsbs is the
largest size we want to scan, not one past that. Put another way, this
loop is actually 1-indexed, not 0-indexed. Therefore, the continuation
test should use <=, not <.

As a result, online repairs of btree blocks fails to stale any buffers
for btrees that are being torn down, which causes later assertions in
the buffer cache when another thread creates a different-sized buffer.
This happens in xfs/709 when allocating an inode cluster buffer:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 3346128 at fs/xfs/xfs_message.c:104 assfail+0x3a/0x40 [xfs]
CPU: 0 PID: 3346128 Comm: fsstress Not tainted 6.7.0-rc4-djwx #rc4
RIP: 0010:assfail+0x3a/0x40 [xfs]
Call Trace:
<TASK>
_xfs_buf_obj_cmp+0x4a/0x50
xfs_buf_get_map+0x191/0xba0
xfs_trans_get_buf_map+0x136/0x280
xfs_ialloc_inode_init+0x186/0x340
xfs_ialloc_ag_alloc+0x254/0x720
xfs_dialloc+0x21f/0x870
xfs_create_tmpfile+0x1a9/0x2f0
xfs_rename+0x369/0xfd0
xfs_vn_rename+0xfa/0x170
vfs_rename+0x5fb/0xc30
do_renameat2+0x52d/0x6e0
__x64_sys_renameat2+0x4b/0x60
do_syscall_64+0x3b/0xe0
entry_SYSCALL_64_after_hwframe+0x46/0x4e

A later refactoring patch in the online repair series fixed this by
accident, which is why I didn't notice this until I started testing only
the patches that are likely to end up in 6.8.

Fixes: 1c7ce115e521 ("xfs: reap large AG metadata extents when possible")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/xfs/scrub/reap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/xfs/scrub/reap.c
+++ b/fs/xfs/scrub/reap.c
@@ -247,7 +247,7 @@ xreap_agextent_binval(
max_fsbs = min_t(xfs_agblock_t, agbno_next - bno,
xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX));

- for (fsbcount = 1; fsbcount < max_fsbs; fsbcount++) {
+ for (fsbcount = 1; fsbcount <= max_fsbs; fsbcount++) {
struct xfs_buf *bp = NULL;
xfs_daddr_t daddr;
int error;