ocfs2: fix deadlock in inline-data truncate transactions

Updating an inode xattr can cause an ABBA deadlock with inline file
truncation:

  ocfs2_truncate_file()
    down_write(&oi->ip_alloc_sem)
    ocfs2_truncate_inline()
      ocfs2_start_trans()

  ocfs2_xattr_set()
    ocfs2_start_trans()
    ocfs2_xattr_ibody_set()
      down_write(&oi->ip_alloc_sem)

The xattr set path starts the merged transaction before the inode-body
xattr helper acquires ip_alloc_sem, reversing the ip_alloc_sem ->
transaction order used by the allocation and truncate paths.  The
transaction merge in commit 85db90e77806 ("ocfs2/xattr: Merge xattr set
transaction.") introduced this ordering.

Fix it by acquiring ip_alloc_sem once in ocfs2_xattr_set(), before xattr
preparation, allocation reservations and ocfs2_start_trans(), and removing
the per-helper acquisition from ocfs2_xattr_ibody_find(),
ocfs2_xattr_ibody_set() and ocfs2_xattr_create_index_block().  These
helpers now assert via lockdep that the caller holds ip_alloc_sem.

ocfs2_xattr_set_handle(), which only sets initial ACL or security xattrs
on unpublished inodes inside the create transaction, takes ip_alloc_sem
under a dedicated lockdep subclass so that the assertions hold without
creating a transaction -> ip_alloc_sem cycle against the ip_alloc_sem ->
transaction order.  The inode is unpublished, so the acquisition can never
contend.

This keeps the established ip_alloc_sem -> transaction order and makes the
locking unconditional, so lockdep can verify a single plain ordering
instead of conditional acquisitions.

Link: https://lore.kernel.org/20260826112659.246574-1-joseph.qi@linux.alibaba.com
Fixes: 85db90e77806 ("ocfs2/xattr: Merge xattr set transaction.")
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: ZhengYuan Huang <gality369@gmail.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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions