[LU-19536] fault_in_iov_iter_readable() with a spinlock held

• Type: Bug
• Resolution: Unresolved
• Priority: Medium
• Severity: 3
• Assignee: Patrick Farrell
• Reporter: Alex Zhuravlev

Description

in LU-13805 and LU-18006 the following code was introduced:

       if (rw == WRITE) {
               spin_lock(&sdio->csd_lock);
...
       /* fault in the entire userspace iovec */
       if (rw == WRITE) {
               if (unlikely(ll_iov_iter_fault_in_readable(iter, count)))

I think it's a bad idea to repopulate userspace pages holding a spinlock - this can involve page allocation and I/O.