ipc/sem: use flexible array in 'struct sem_undo'

Turn 'semadj' in 'struct sem_undo' into a flexible array.

The advantages are:
   - save the size of a pointer when the new undo structure is allocated
   - avoid some always ugly pointer arithmetic to get the address of semadj
   - avoid an indirection when the array is accessed

While at it, use struct_size() to compute the size of the new undo
structure.

Link: https://lkml.kernel.org/r/1ba993d443ad7e16ac2b1902adab1f05ebdfa454.1688918791.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <[email protected]>
Reviewed-by: Manfred Spraul <[email protected]>
Reviewed-by: Davidlohr Bueso <[email protected]>
Cc: Christophe JAILLET <[email protected]>
Cc: Jann Horn <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions