Linux 4.3 compat: bio_end_io_t / BIO_UPTODATE

Commit torvalds/linux@4246a0b63bd8f56a1469b12eafeb875b1041a451
("block: add a bi_error field to struct bio") dropped the error
argument from bio_endio in favor of newly introduced bio->bi_error.
This also replaces bio->bi_flags value BIO_UPTODATE.

bio_endio was a 3 argument function until Linux 2.6.24, which made it
a 2 argument function, and now the prototype has changed yet again to
a 1 argument function. Support for pre 2.6.24 kernels was already
dropped with 37f9dac592bf ("zvol processing should use struct bio")
which assumed the 2 argument version in zvol_request(). Remaining code
to support the 3 argument version is hereby removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Issue #3799

zfs/config/kernel-bio-end-io-t-args.m4

 dnl #
-dnl # 2.6.24 API change
-dnl # Size argument dropped from bio_endio and bi_end_io, because the
-dnl # bi_end_io is only called once now when the request is complete.
-dnl # There is no longer any need for a size argument.  This also means
-dnl # that partial IO's are no longer possibe and the end_io callback
-dnl # should not check bi->bi_size.  Finally, the return type was updated
-dnl # to void.
+dnl # 4.3 API change
+dnl # Error argument dropped from bio_endio in favor of newly introduced
+dnl # bio->bi_error. This also replaces bio->bi_flags value BIO_UPTODATE.
+dnl # Introduced by torvalds/linux@4246a0b63bd8f56a1469b12eafeb875b1041a451
+dnl # ("block: add a bi_error field to struct bio").
 dnl #
 AC_DEFUN([ZFS_AC_KERNEL_BIO_END_IO_T_ARGS], [
-	AC_MSG_CHECKING([whether bio_end_io_t wants 2 args])
+	AC_MSG_CHECKING([whether bio_end_io_t wants 1 arg])
 	ZFS_LINUX_TRY_COMPILE([
 		#include <linux/bio.h>
 
-		void wanted_end_io(struct bio *bio, int x) { return; }
+		void wanted_end_io(struct bio *bio) { return; }
 
 		bio_end_io_t *end_io __attribute__ ((unused)) = wanted_end_io;
 	],[
 	],[
 		AC_MSG_RESULT(yes)
-		AC_DEFINE(HAVE_2ARGS_BIO_END_IO_T, 1,
-		          [bio_end_io_t wants 2 args])
+		AC_DEFINE(HAVE_1ARG_BIO_END_IO_T, 1,
+			  [bio_end_io_t wants 1 arg])
 	],[
 		AC_MSG_RESULT(no)
 	])

zfs/include/linux/blkdev_compat.h

@@ -377,20 +377,17 @@ bio_set_flags_failfast(struct block_device *bdev, int *flags)
 #endif /* DISK_NAME_LEN */
 
 /*
- * 2.6.24 API change,
- * The bio_end_io() prototype changed slightly.  These are helper
- * macro's to ensure the prototype and return value are handled.
+ * 4.3 API change
+ * The bio_endio() prototype changed slightly.  These are helper
+ * macro's to ensure the prototype and invocation are handled.
  */
-#ifdef HAVE_2ARGS_BIO_END_IO_T
-#define	BIO_END_IO_PROTO(fn, x, y, z)	static void fn(struct bio *x, int z)
-#define	BIO_END_IO_RETURN(rc)		return
+#ifdef HAVE_1ARG_BIO_END_IO_T
+#define	BIO_END_IO_PROTO(fn, x, z)	static void fn(struct bio *x)
+#define	BIO_END_IO(bio, error)		bio->bi_error = error; bio_endio(bio);
 #else
-#define	BIO_END_IO_PROTO(fn, x, y, z)	static int fn( \
-					    struct bio *x, \
-					    unsigned int y, \
-					    int z)
-#define	BIO_END_IO_RETURN(rc)		return rc
-#endif /* HAVE_2ARGS_BIO_END_IO_T */
+#define	BIO_END_IO_PROTO(fn, x, z)	static void fn(struct bio *x, int z)
+#define	BIO_END_IO(bio, error)		bio_endio(bio, error);
+#endif /* HAVE_1ARG_BIO_END_IO_T */
 
 /*
  * 2.6.38 - 2.6.x API,

zfs/module/zfs/vdev_disk.c

@@ -421,21 +421,21 @@ vdev_disk_dio_put(dio_request_t *dr)
 	return (rc);
 }
 
-BIO_END_IO_PROTO(vdev_disk_physio_completion, bio, size, error)
+BIO_END_IO_PROTO(vdev_disk_physio_completion, bio, error)
 {
 	dio_request_t *dr = bio->bi_private;
 	int rc;
 
-#ifndef HAVE_2ARGS_BIO_END_IO_T
-	if (BIO_BI_SIZE(bio))
-		return (1);
-#endif /* HAVE_2ARGS_BIO_END_IO_T */
-
-	if (error == 0 && !test_bit(BIO_UPTODATE, &bio->bi_flags))
-		error = (-EIO);
-
-	if (dr->dr_error == 0)
-		dr->dr_error = -error;
+	if (dr->dr_error == 0) {
+#ifdef HAVE_1ARG_BIO_END_IO_T
+		dr->dr_error = -(bio->bi_error);
+#else
+		if (error)
+			dr->dr_error = -(error);
+		else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+			dr->dr_error = EIO;
+#endif
+	}
 
 	/* Drop reference aquired by __vdev_disk_physio */
 	rc = vdev_disk_dio_put(dr);
@@ -443,8 +443,6 @@ BIO_END_IO_PROTO(vdev_disk_physio_completion, bio, size, error)
 	/* Wake up synchronous waiter this is the last outstanding bio */
 	if ((rc == 1) && vdev_disk_dio_is_sync(dr))
 		complete(&dr->dr_comp);
-
-	BIO_END_IO_RETURN(0);
 }
 
 static inline unsigned long
@@ -605,9 +603,12 @@ vdev_disk_physio(struct block_device *bdev, caddr_t kbuf,
 	return (__vdev_disk_physio(bdev, NULL, kbuf, size, offset, flags));
 }
 
-BIO_END_IO_PROTO(vdev_disk_io_flush_completion, bio, size, rc)
+BIO_END_IO_PROTO(vdev_disk_io_flush_completion, bio, rc)
 {
 	zio_t *zio = bio->bi_private;
+#ifdef HAVE_1ARG_BIO_END_IO_T
+	int rc = bio->bi_error;
+#endif
 
 	zio->io_delay = jiffies_64 - zio->io_delay;
 	zio->io_error = -rc;
@@ -619,8 +620,6 @@ BIO_END_IO_PROTO(vdev_disk_io_flush_completion, bio, size, rc)
 	if (zio->io_error)
 		vdev_disk_error(zio);
 	zio_interrupt(zio);
-
-	BIO_END_IO_RETURN(0);
 }
 
 static int