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From 01077c81987011d8a50999824f96032c10b2733b Mon Sep 17 00:00:00 2001
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From: Josef Bacik <jbacik@fusionio.com>
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Date: Thu, 21 Jun 2012 16:02:10 -0400
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Subject: [PATCH 1/3] Btrfs-progs: add btrfs device ready command
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This command will be used by things like dracut that wish to know very
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simply if all of the devices have been added to the kernel cache yet for the
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device to be fully mounted.  This keeps initrd's from constantly having to
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try to mount the file system until it succeeds every time a device is added
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to the system.  Thanks,
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Signed-off-by: Josef Bacik <jbacik@fusionio.com>
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---
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 cmds-device.c |   35 +++++++++++++++++++++++++++++++++++
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 ioctl.h       |    2 ++
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 2 files changed, 37 insertions(+), 0 deletions(-)
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diff --git a/cmds-device.c b/cmds-device.c
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index 771856b..b24e2a3 100644
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--- a/cmds-device.c
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+++ b/cmds-device.c
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@@ -249,11 +249,46 @@ static int cmd_scan_dev(int argc, char **argv)
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 	return 0;
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 }
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+static const char * const cmd_ready_dev_usage[] = {
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+	"btrfs device ready <device>",
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+	"Check device to see if it has all of it's devices in cache for mounting",
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+	NULL
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+};
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+
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+static int cmd_ready_dev(int argc, char **argv)
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+{
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+	struct	btrfs_ioctl_vol_args args;
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+	int	fd;
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+	int	ret;
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+
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+	if (check_argc_min(argc, 2))
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+		usage(cmd_ready_dev_usage);
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+
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+	fd = open("/dev/btrfs-control", O_RDWR);
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+	if (fd < 0) {
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+		perror("failed to open /dev/btrfs-control");
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+		return 10;
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+	}
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+
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+	strncpy(args.name, argv[argc - 1], BTRFS_PATH_NAME_MAX);
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+	ret = ioctl(fd, BTRFS_IOC_DEVICES_READY, &args);
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+	if (ret < 0) {
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+		fprintf(stderr, "ERROR: unable to determine if the device '%s'"
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+			" is ready for mounting - %s\n", argv[argc - 1],
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+			strerror(errno));
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+		ret = 1;
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+	}
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+
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+	close(fd);
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+	return ret;
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+}
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+
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 const struct cmd_group device_cmd_group = {
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 	device_cmd_group_usage, NULL, {
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 		{ "add", cmd_add_dev, cmd_add_dev_usage, NULL, 0 },
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 		{ "delete", cmd_rm_dev, cmd_rm_dev_usage, NULL, 0 },
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 		{ "scan", cmd_scan_dev, cmd_scan_dev_usage, NULL, 0 },
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+		{ "ready", cmd_ready_dev, cmd_ready_dev_usage, NULL, 0 },
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 		{ 0, 0, 0, 0, 0 }
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 	}
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 };
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diff --git a/ioctl.h b/ioctl.h
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index d6f3d07..30220ad 100644
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--- a/ioctl.h
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+++ b/ioctl.h
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@@ -365,6 +365,8 @@ struct btrfs_ioctl_clone_range_args {
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 					struct btrfs_ioctl_ino_path_args)
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 #define BTRFS_IOC_LOGICAL_INO _IOWR(BTRFS_IOCTL_MAGIC, 36, \
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 					struct btrfs_ioctl_ino_path_args)
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+#define BTRFS_IOC_DEVICES_READY _IOR(BTRFS_IOCTL_MAGIC, 39, \
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+				     struct btrfs_ioctl_vol_args)
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 #define BTRFS_IOC_SET_RECEIVED_SUBVOL _IOWR(BTRFS_IOCTL_MAGIC, 37, \
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 				struct btrfs_ioctl_received_subvol_args)
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-- 
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1.7.7.6
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