5.3.0 compat / rwlock

[c0d3z3r0]

System information

Type	Version/Name
Distribution Name	Debian
Distribution Version	testing
Linux Kernel	5.2.0
Architecture	amd64
ZFS Version	master (d230a65)
SPL Version	-

Describe the problem you're observing

ZFS builds fine in-tree with linux 5.2.0-rc7. 5.2.0 fails:

  CC      fs/zfs/icp/illumos-crypto.o
  CC      fs/zfs/lua/lapi.o
  CC      fs/zfs/nvpair/nvpair.o
  CC      fs/zfs/icp/api/kcf_cipher.o
In file included from ./include/zfs/spl/sys/taskq.h:35,
                 from ./include/zfs/spl/sys/kmem_cache.h:28,
                 from ./include/zfs/sys/zfs_context.h:41,
                 from ./include/zfs/sys/crypto/common.h:39,
                 from fs/zfs/icp/illumos-crypto.c:35:
./include/zfs/spl/sys/rwlock.h: In function ‘rw_owner’:
./include/zfs/spl/sys/rwlock.h:121:18: error: incompatible types when returning type ‘atomic_long_t’ {aka ‘struct <anonymous>’} but ‘kthread_t *’ {aka ‘struct task_struct *’} was expected
  return (SEM(rwp)->owner);
         ~~~~~~~~~^~~~~~~~
./include/zfs/spl/sys/rwlock.h: In function ‘RW_READ_HELD’:
./include/zfs/spl/sys/rwlock.h:199:26: warning: comparison between pointer and integer
  if (RWSEM_OWNER_UNKNOWN == (struct task_struct *)-2L) {
                          ^~
./include/zfs/spl/sys/rwlock.h:201:3: error: aggregate value used where an integer was expected
   return ((unsigned long) SEM(rwp)->owner & 1);
   ^~~~~~
In file included from ./include/zfs/spl/sys/taskq.h:35,
                 from ./include/zfs/spl/sys/kmem_cache.h:28,
                 from ./include/zfs/sys/zfs_context.h:41,
                 from ./include/zfs/sys/lua/lua.h:13,
                 from fs/zfs/lua/lapi.c:12:
./include/zfs/spl/sys/rwlock.h: In function ‘rw_owner’:
./include/zfs/spl/sys/rwlock.h:121:18: error: incompatible types when returning type ‘atomic_long_t’ {aka ‘struct <anonymous>’} but ‘kthread_t *’ {aka ‘struct task_struct *’} was expected
  return (SEM(rwp)->owner);
         ~~~~~~~~~^~~~~~~~
./include/zfs/spl/sys/rwlock.h: In function ‘RW_READ_HELD’:
./include/zfs/spl/sys/rwlock.h:199:26: warning: comparison between pointer and integer
  if (RWSEM_OWNER_UNKNOWN == (struct task_struct *)-2L) {
                          ^~
./include/zfs/spl/sys/rwlock.h:201:3: error: aggregate value used where an integer was expected
   return ((unsigned long) SEM(rwp)->owner & 1);
   ^~~~~~
make[3]: *** [scripts/Makefile.build:279: fs/zfs/icp/illumos-crypto.o] Error 1
make[3]: *** Waiting for unfinished jobs....
  CC      fs/file_table.o
make[3]: *** [scripts/Makefile.build:279: fs/zfs/lua/lapi.o] Error 1
make[2]: *** [scripts/Makefile.build:489: fs/zfs/lua] Error 2
make[2]: *** Waiting for unfinished jobs....
  CC      fs/super.o
  CC      fs/char_dev.o
In file included from ./include/zfs/spl/sys/taskq.h:35,
                 from ./include/zfs/spl/sys/kmem_cache.h:28,
                 from ./include/zfs/sys/zfs_context.h:41,
                 from fs/zfs/icp/api/kcf_cipher.c:26:
./include/zfs/spl/sys/rwlock.h: In function ‘rw_owner’:
./include/zfs/spl/sys/rwlock.h:121:18: error: incompatible types when returning type ‘atomic_long_t’ {aka ‘struct <anonymous>’} but ‘kthread_t *’ {aka ‘struct task_struct *’} was expected
  return (SEM(rwp)->owner);
         ~~~~~~~~~^~~~~~~~
./include/zfs/spl/sys/rwlock.h: In function ‘RW_READ_HELD’:
./include/zfs/spl/sys/rwlock.h:199:26: warning: comparison between pointer and integer
  if (RWSEM_OWNER_UNKNOWN == (struct task_struct *)-2L) {
                          ^~
./include/zfs/spl/sys/rwlock.h:201:3: error: aggregate value used where an integer was expected
   return ((unsigned long) SEM(rwp)->owner & 1);
   ^~~~~~
make[3]: *** [scripts/Makefile.build:279: fs/zfs/icp/api/kcf_cipher.o] Error 1
make[2]: *** [scripts/Makefile.build:489: fs/zfs/icp] Error 2
  CC      fs/stat.o
  CC      fs/exec.o
  CC      fs/pipe.o
  CC      fs/zfs/nvpair/fnvpair.o
  CC      fs/namei.o
  CC      fs/fcntl.o
  CC      fs/zfs/nvpair/nvpair_alloc_spl.o
  CC      fs/zfs/nvpair/nvpair_alloc_fixed.o
  CC      fs/ioctl.o
  CC      fs/readdir.o
  AR      fs/zfs/nvpair/built-in.a
make[1]: *** [scripts/Makefile.build:489: fs/zfs] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:1071: fs] Error 2
make: *** Waiting for unfinished jobs....

[behlendorf]

@c0d3z3r0 I'm relatively certain you must have been using a commit from after the 5.2 tag. This build failure was caused by https://lkml.org/lkml/2019/7/8/1415 which was just merged for 5.3. The fix looks pretty straight forward, I'll see about getting a PR open in the next couple of days.

[c0d3z3r0]

Well, I am very sure that I used v5.2 tag, but I will check this again later

[kusumi]

I compiled 5.2 (torvalds/linux@0ecfebd) a few days ago, and did not see this. There were compat issues only in -rc1 for 5.2 iirc.

[kusumi]

the exact commit is torvalds/linux@94a9717 which appeared after torvalds/linux@0ecfebd.

 struct rw_semaphore {
        atomic_long_t count;
        /*
-        * Write owner or one of the read owners. Can be used as a
-        * speculative check to see if the owner is running on the cpu.
+        * Write owner or one of the read owners as well flags regarding
+        * the current state of the rwsem. Can be used as a speculative
+        * check to see if the write owner is running on the cpu.
         */
-       struct task_struct *owner;
+       atomic_long_t owner;

[c0d3z3r0]

oh damn. seems I was simply to tired to get this right... thanks