Improve performance for zpool trim on linux

On Linux, ZFS uses blkdev_issue_discard in vdev_disk_io_trim to issue
trim command which is synchronous.

This commit updates vdev_disk_io_trim to use __blkdev_issue_discard,
which is asynchronous. Unfortunately there isn't any asynchronous
version for blkdev_issue_secure_erase, so performance of secure trim
will still suffer.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Umer Saleem <usaleem@ixsystems.com>
Closes #15843

config/kernel-blkdev.m4

@@ -524,6 +524,7 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_BDEVNAME], [
 
 dnl #
 dnl # 5.19 API: blkdev_issue_secure_erase()
+dnl # 4.7  API: __blkdev_issue_discard(..., BLKDEV_DISCARD_SECURE)
 dnl # 3.10 API: blkdev_issue_discard(..., BLKDEV_DISCARD_SECURE)
 dnl #
 AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_ISSUE_SECURE_ERASE], [
@@ -539,6 +540,20 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_ISSUE_SECURE_ERASE], [
 		    sector, nr_sects, GFP_KERNEL);
 	])
 
+	ZFS_LINUX_TEST_SRC([blkdev_issue_discard_async_flags], [
+		#include <linux/blkdev.h>
+	],[
+		struct block_device *bdev = NULL;
+		sector_t sector = 0;
+		sector_t nr_sects = 0;
+		unsigned long flags = 0;
+		struct bio *biop = NULL;
+		int error __attribute__ ((unused));
+
+		error = __blkdev_issue_discard(bdev,
+		    sector, nr_sects, GFP_KERNEL, flags, &biop);
+	])
+
 	ZFS_LINUX_TEST_SRC([blkdev_issue_discard_flags], [
 		#include <linux/blkdev.h>
 	],[
@@ -562,6 +577,14 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_ISSUE_SECURE_ERASE], [
 	],[
 		AC_MSG_RESULT(no)
 
+		AC_MSG_CHECKING([whether __blkdev_issue_discard() is available])
+		ZFS_LINUX_TEST_RESULT([blkdev_issue_discard_async_flags], [
+			AC_MSG_RESULT(yes)
+			AC_DEFINE(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC, 1,
+			    [__blkdev_issue_discard() is available])
+		],[
+			AC_MSG_RESULT(no)
+
 			AC_MSG_CHECKING([whether blkdev_issue_discard() is available])
 			ZFS_LINUX_TEST_RESULT([blkdev_issue_discard_flags], [
 				AC_MSG_RESULT(yes)
@@ -571,6 +594,7 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_ISSUE_SECURE_ERASE], [
 				ZFS_LINUX_TEST_ERROR([blkdev_issue_discard()])
 			])
 		])
+	])
 ])
 
 dnl #

module/os/linux/zfs/vdev_disk.c

@@ -862,27 +862,66 @@ vdev_disk_io_flush(struct block_device *bdev, zio_t *zio)
 	return (0);
 }
 
+#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE) || \
+	defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC)
+BIO_END_IO_PROTO(vdev_disk_discard_end_io, bio, error)
+{
+	zio_t *zio = bio->bi_private;
+#ifdef HAVE_1ARG_BIO_END_IO_T
+	zio->io_error = BIO_END_IO_ERROR(bio);
+#else
+	zio->io_error = -error;
+#endif
+	bio_put(bio);
+	if (zio->io_error)
+		vdev_disk_error(zio);
+	zio_interrupt(zio);
+}
+
+static int
+vdev_issue_discard_trim(zio_t *zio, unsigned long flags)
+{
+	int ret;
+	struct bio *bio = NULL;
+
+#if defined(BLKDEV_DISCARD_SECURE)
+	ret = - __blkdev_issue_discard(
+	    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
+	    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS, flags, &bio);
+#else
+	(void) flags;
+	ret = - __blkdev_issue_discard(
+	    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
+	    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS, &bio);
+#endif
+	if (!ret && bio) {
+		bio->bi_private = zio;
+		bio->bi_end_io = vdev_disk_discard_end_io;
+		vdev_submit_bio(bio);
+	}
+	return (ret);
+}
+#endif
+
 static int
 vdev_disk_io_trim(zio_t *zio)
 {
-	vdev_t *v = zio->io_vd;
-	vdev_disk_t *vd = v->vdev_tsd;
-
-#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE)
-	if (zio->io_trim_flags & ZIO_TRIM_SECURE) {
-		return (-blkdev_issue_secure_erase(BDH_BDEV(vd->vd_bdh),
-		    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS));
-	} else {
-		return (-blkdev_issue_discard(BDH_BDEV(vd->vd_bdh),
-		    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS));
-	}
-#elif defined(HAVE_BLKDEV_ISSUE_DISCARD)
 	unsigned long trim_flags = 0;
-#if defined(BLKDEV_DISCARD_SECURE)
+	if (zio->io_trim_flags & ZIO_TRIM_SECURE) {
-	if (zio->io_trim_flags & ZIO_TRIM_SECURE)
+#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE)
+		return (-blkdev_issue_secure_erase(
+		    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
+		    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS));
+#elif defined(BLKDEV_DISCARD_SECURE)
 		trim_flags |= BLKDEV_DISCARD_SECURE;
 #endif
-	return (-blkdev_issue_discard(BDH_BDEV(vd->vd_bdh),
+	}
+#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE) || \
+	defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC)
+	return (vdev_issue_discard_trim(zio, trim_flags));
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD)
+	return (-blkdev_issue_discard(
+	    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
 	    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS, trim_flags));
 #else
 #error "Unsupported kernel"
@@ -968,7 +1007,12 @@ vdev_disk_io_start(zio_t *zio)
 	case ZIO_TYPE_TRIM:
 		zio->io_error = vdev_disk_io_trim(zio);
 		rw_exit(&vd->vd_lock);
+#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE)
+		if (zio->io_trim_flags & ZIO_TRIM_SECURE)
 			zio_interrupt(zio);
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD)
+		zio_interrupt(zio);
+#endif
 		return;
 
 	default: