[PATCH] r/o bind mounts: fix buggy loop

The mnt->__mnt_writers can go negative for a time if a pair of mnt_want_write()/mnt_drop_write() calls is done on a different cpu, but for the same mount. This part is expected. The lock_and_coalesce..() function should make that count positive (or at least 0). Hugh Dickins had found a bug in

[PATCH] r/o bind mounts: fix buggy loop

The mnt-__mnt_writers can go negative for a time if a pair of mnt_want_write()/mnt_drop_write() calls is done on a different cpu, but for the same mount. This part is expected. The lock_and_coalesce..() function should make that count positive (or at least 0). Hugh Dickins had found a bug in