[PATCH 2/2] btrfs-progs: replace: New argument to resize the fs after replace

[Marcos Paulo de Souza <marcos@mpdesouza.com>]

From: Marcos Paulo de Souza <mpdesouza@suse.com>

By using the -a flag on replace makes btrfs issue a resize ioctl after
the replace finishes. This argument is a shortcut for

btrfs replace start -f 3 /dev/sdf BTRFS/
btrfs fi resize 3:max BTRFS/

The -a stands for "automatically resize"

Fixes: #21

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
 Documentation/btrfs-replace.asciidoc |  4 +++-
 cmds/replace.c                       | 19 +++++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/Documentation/btrfs-replace.asciidoc b/Documentation/btrfs-replace.asciidoc
index b73bf1b3..e0b30066 100644
--- a/Documentation/btrfs-replace.asciidoc
+++ b/Documentation/btrfs-replace.asciidoc
@@ -18,7 +18,7 @@ SUBCOMMAND
 *cancel* <mount_point>::
 Cancel a running device replace operation.
 
-*start* [-Bfr] <srcdev>|<devid> <targetdev> <path>::
+*start* [-aBfr] <srcdev>|<devid> <targetdev> <path>::
 Replace device of a btrfs filesystem.
 +
 On a live filesystem, duplicate the data to the target device which
@@ -53,6 +53,8 @@ never allowed to be used as the <targetdev>.
 +
 -B::::
 no background replace.
++a::::
+automatically resizes the filesystem if the <targetdev> is bigger than <srcdev>.
 
 *status* [-1] <mount_point>::
 Print status and progress information of a running device replace operation.
diff --git a/cmds/replace.c b/cmds/replace.c
index 2321aa15..48f470cd 100644
--- a/cmds/replace.c
+++ b/cmds/replace.c
@@ -91,7 +91,7 @@ static int dev_replace_handle_sigint(int fd)
 }
 
 static const char *const cmd_replace_start_usage[] = {
-	"btrfs replace start [-Bfr] <srcdev>|<devid> <targetdev> <mount_point>",
+	"btrfs replace start [-aBfr] <srcdev>|<devid> <targetdev> <mount_point>",
 	"Replace device of a btrfs filesystem.",
 	"On a live filesystem, duplicate the data to the target device which",
 	"is currently stored on the source device. If the source device is not",
@@ -104,6 +104,8 @@ static const char *const cmd_replace_start_usage[] = {
 	"from the system, you have to use the <devid> parameter format.",
 	"The <targetdev> needs to be same size or larger than the <srcdev>.",
 	"",
+	"-a     automatically resize the filesystem if the <targetdev> is bigger",
+	"       than <srcdev>",
 	"-r     only read from <srcdev> if no other zero-defect mirror exists",
 	"       (enable this if your drive has lots of read errors, the access",
 	"       would be very slow)",
@@ -129,6 +131,7 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 	char *path;
 	char *srcdev;
 	char *dstdev = NULL;
+	bool auto_resize = false;
 	int avoid_reading_from_srcdev = 0;
 	int force_using_targetdev = 0;
 	u64 dstdev_block_count;
@@ -138,8 +141,11 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 	u64 dstdev_size;
 
 	optind = 0;
-	while ((c = getopt(argc, argv, "Brf")) != -1) {
+	while ((c = getopt(argc, argv, "aBrf")) != -1) {
 		switch (c) {
+		case 'a':
+			auto_resize = true;
+			break;
 		case 'B':
 			do_not_background = 1;
 			break;
@@ -309,6 +315,15 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 			goto leave_with_error;
 		}
 	}
+
+	if (ret == 0 && auto_resize && dstdev_size > srcdev_size) {
+		char amount[BTRFS_PATH_NAME_MAX + 1];
+		snprintf(amount, BTRFS_PATH_NAME_MAX, "%s:max", srcdev);
+
+		if (resize_filesystem(amount, path))
+			goto leave_with_error;
+	}
+
 	close_file_or_dir(fdmnt, dirstream);
 	return 0;
 
-- 
2.25.0