ocfs2: fix cached cluster count after suballocator reclaim

When reclaiming a suballocator block group, first reduce the on-disk
cluster count by cl_cpg.  The current code then subtracts that new count
(fe->i_clusters) from the old cached count
(OCFS2_I(alloc_inode)->ip_clusters).

For an allocator with N block groups, that leaves the cache at

    N * cl_cpg - (N * cl_cpg - cl_cpg) = cl_cpg

i.e.  ip_clusters -= (fe->i_clusters - cl_cpg) leaves ip_clusters equal to
cl_cpg regardless of N.  This happens to be correct when reclaiming from
two block groups, but undercounts the clusters from three block groups
onwards.  The incorrect cache value is also used immediately to update
i_blocks.

Assign the updated on-disk count to the cache, matching the allocation and
inode refresh paths.

In a QEMU test using a clean 256 MiB OCFS2 image and a 10,000-file
create/delete workload, the first buggy reclaim left the on-disk
(fe->i_clusters) and cached (ip_clusters) counts at 2048 and 512 clusters
respectively; later reclaims underflowed the cache.  With this change, the
cache matched the on-disk count across all four reclaims: 2048, 1536,
1024, and 512 clusters.

Link: https://lore.kernel.org/20260805113920.385959-1-matthias.goergens@gmail.com
Fixes: 4a54331616b3 ("ocfs2: give ocfs2 the ability to reclaim suballocator free bg")
Signed-off-by: Matthias Goergens <matthias.goergens@gmail.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions