From 7e8a6edb4d1ba0079152eb477abbbc1dfb1ebb7e Mon Sep 17 00:00:00 2001
From: Pavel Reichl <preichl@redhat.com>
Date: Fri, 13 Dec 2019 16:21:26 -0500
Subject: [PATCH] mkfs: Break block discard into chunks of 2 GB

Some users are not happy about the BLKDISCARD taking too long and at the
same time not being informed about that - so they think that the command
actually hung.

This commit changes code so that progress reporting is possible and also
typing the ^C will cancel the ongoing BLKDISCARD.

Signed-off-by: Pavel Reichl <preichl@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 mkfs/xfs_mkfs.c | 50 ++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 37 insertions(+), 13 deletions(-)

Index: xfsprogs-4.5.0/mkfs/xfs_mkfs.c
===================================================================
--- xfsprogs-4.5.0.orig/mkfs/xfs_mkfs.c
+++ xfsprogs-4.5.0/mkfs/xfs_mkfs.c
@@ -875,17 +875,41 @@ done:
 }
 
 static void
-discard_blocks(dev_t dev, __uint64_t nsectors)
+discard_blocks(dev_t dev, __uint64_t nsectors, int quiet)
 {
-	int fd;
+	int		fd;
+	uint64_t	offset = 0;
+	/* Discard the device 2G at a time */
+	const __uint64_t step = 2ULL << 30;
+	const __uint64_t count = BBTOB(nsectors);
 
-	/*
-	 * We intentionally ignore errors from the discard ioctl.  It is
-	 * not necessary for the mkfs functionality but just an optimization.
-	 */
 	fd = libxfs_device_to_fd(dev);
-	if (fd > 0)
-		platform_discard_blocks(fd, 0, nsectors << 9);
+	if (fd <= 0)
+		return;
+	if (!quiet) {
+		printf("Discarding blocks...");
+		fflush(stdout);
+	}
+
+	/* The block discarding happens in smaller batches so it can be
+	 * interrupted prematurely
+	 */
+	while (offset < count) {
+		__uint64_t	tmp_step = min(step, count - offset);
+
+		/*
+		 * We intentionally ignore errors from the discard ioctl. It is
+		 * not necessary for the mkfs functionality but just an
+		 * optimization. However we should stop on error.
+		 */
+		if (platform_discard_blocks(fd, offset, tmp_step))
+			return;
+
+		offset += tmp_step;
+	}
+	if (!quiet)
+		printf("Done.\n");
+
 }
 
 int
@@ -2140,11 +2164,11 @@ _("warning: sparse inodes not supported
 	}
 
 	if (discard && !Nflag) {
-		discard_blocks(xi.ddev, xi.dsize);
+		discard_blocks(xi.ddev, xi.dsize, qflag);
 		if (xi.rtdev)
-			discard_blocks(xi.rtdev, xi.rtsize);
+			discard_blocks(xi.rtdev, xi.rtsize, qflag);
 		if (xi.logdev && xi.logdev != xi.ddev)
-			discard_blocks(xi.logdev, xi.logBBsize);
+			discard_blocks(xi.logdev, xi.logBBsize, qflag);
 	}
 
 	if (!liflag && !ldflag)