X Fix mlock2 build on Debian 8

@rporchetto reports build failure on Debian 8 / Linux 3.16

    [2021-07-30 15:40:35,677] INFO     gcc -pthread -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/srv/slapgrid/slappart19/srv/runner/shared/python2.7/3b7a074d1ded44046871b13502341482/include/python2.7 -c wcfs/internal/mm.c -o build/temp.linux-x86_64-2.7/wcfs/internal/mm.o
    [2021-07-30 15:40:35,677] INFO     wcfs/internal/mm.c: In function 'mlock2':
    [2021-07-30 15:40:35,677] INFO     wcfs/internal/mm.c:618:28: error: 'SYS_mlock2' undeclared (first use in this function); did you mean 'SYS_mlock'?
    [2021-07-30 15:40:35,677] INFO              long err = syscall(SYS_mlock2, addr, len, flags);
    [2021-07-30 15:40:35,677] INFO                                 ^~~~~~~~~~
    [2021-07-30 15:40:35,677] INFO                                 SYS_mlock

Fix the build.

NOTE mlock2 was added in Linux 4.3.

Similarly MCL_ONFAULT is not provided on that old glibc 2.19:

    [2021-07-30 15:40:35,677] INFO     wcfs/internal/mm.c:986:55: error: 'MCL_ONFAULT' undeclared here (not in a function); did you mean 'MLOCK_ONFAULT'?
    [2021-07-30 15:40:35,677] INFO        __pyx_e_8wendelin_4wcfs_8internal_2mm_MCL_ONFAULT = MCL_ONFAULT,
    [2021-07-30 15:40:35,678] INFO                                                            ^~~~~~~~~~~
    [2021-07-30 15:40:35,678] INFO                                                            MLOCK_ONFAULT

-> Comment MCL_ONFAULT for now since we do not actually use it anywhere yet.

wcfs/internal/mm.pyx

@@ -33,12 +33,17 @@ cdef extern from *:
     #include <unistd.h>
     #include <sys/syscall.h>
     static int mlock2(const void *addr, size_t len, int flags) {
+    #ifndef SYS_mlock2
+        errno = ENOSYS;
+        return -1;
+    #else
         long err = syscall(SYS_mlock2, addr, len, flags);
         if (err != 0) {
             errno = -err;
             return -1;
         }
         return 0;
+    #endif
     }
     #endif
     #endif
@@ -62,7 +67,7 @@ cpdef enum:
     MLOCK_ONFAULT   = mman.MLOCK_ONFAULT
     MCL_CURRENT     = mman.MCL_CURRENT
     MCL_FUTURE      = mman.MCL_FUTURE
-    MCL_ONFAULT     = mman.MCL_ONFAULT
+    #MCL_ONFAULT     = mman.MCL_ONFAULT
 
     MADV_NORMAL     = mman.MADV_NORMAL
     MADV_RANDOM     = mman.MADV_RANDOM

[Roque]

I confirm this commit fixes the build failure. Thank you @kirr !

[Kirill Smelkov]

You are welcome. Thanks for feedback, @rporchetto.