[LU-16890] allow OBD_FREE() to ignore NULL pointers

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0
• Labels: easy
• Severity: 3
• Assignee: Arshad Hussain
• Reporter: Andreas Dilger

Description

The OBD_FREE(ptr) macro will internally (via OBD_FREE_PRE()) assert that ptr != NULL, even though the kernel accepts kfree(NULL) without complaint.

It would make sense to remove the LASSERT(ptr) call from OBD_FREE_PRE() and change the callers to silently accept this case:

#define OBD_FREE(ptr, size)                                                  \
if (likely(ptr)) {                                                           \
        OBD_FREE_PRE(ptr, size, "kfreed");                                   \
        POISON(ptr, 0x5a, size);                                             \
        kfree(ptr);                                                          \
        POISON_PTR(ptr);                                                     \
}

#define OBD_SLAB_FREE(ptr, slab, size)                                       \
if (likely(ptr)) {                                                           \
        OBD_FREE_PRE(ptr, size, "slab-freed");                               \
        POISON(ptr, 0x5a, size);                                             \
        kmem_cache_free(slab, ptr);                                          \
        POISON_PTR(ptr);                                                     \
}

It isn't strictly needed for OBD_FREE_LARGE() since is_vmalloc_addr(ptr) will return false for a NULL pointer and fall back to OBD_FREE().

Issue Links

• is related to: LU-16688 Client crash due to an assertion in lite_lib.c:3394
• is related to: LU-18141 Free'ing macros already check NULL