Re: [PATCH 1/8] btrfs-progs: quota: Add -W option to rescan to wait without starting rescan

[Nikolay Borisov <nborisov@suse.com>]

On  2.03.2018 20:46, jeffm@suse.com wrote:
> From: Jeff Mahoney <jeffm@suse.com>
> 
> This patch adds a new -W option to wait for a rescan without starting a
> new operation.  This is useful for things like xfstests where we want
> do to do a "btrfs quota enable" and not continue until the subsequent
> rescan has finished.
> 
> In addition to documenting the new option in the man page, I've cleaned
> up the rescan entry to document the -w option a bit better.
> 
> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
> ---
>  Documentation/btrfs-quota.asciidoc | 10 +++++++---
>  cmds-quota.c                       | 21 +++++++++++++++------
>  2 files changed, 22 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/btrfs-quota.asciidoc b/Documentation/btrfs-quota.asciidoc
> index 85ebf729..0b64a69b 100644
> --- a/Documentation/btrfs-quota.asciidoc
> +++ b/Documentation/btrfs-quota.asciidoc
> @@ -238,15 +238,19 @@ Disable subvolume quota support for a filesystem.
>  *enable* <path>::
>  Enable subvolume quota support for a filesystem.
>  
> -*rescan* [-s] <path>::
> +*rescan* [-s|-w|-W] <path>::
>  Trash all qgroup numbers and scan the metadata again with the current config.
>  +
>  `Options`
>  +
>  -s::::
> -show status of a running rescan operation.
> +Show status of a running rescan operation.
> +
>  -w::::
> -wait for rescan operation to finish(can be already in progress).
> +Start rescan operation and wait until it has finished before exiting.  If a rescan is already running, wait until it finishes and then exit without starting a new one.
> +
> +-W::::
> +Wait for rescan operation to finish and then exit.  If a rescan is not already running, exit silently.
>  
>  EXIT STATUS
>  -----------
> diff --git a/cmds-quota.c b/cmds-quota.c
> index 745889d1..fe6376ac 100644
> --- a/cmds-quota.c
> +++ b/cmds-quota.c
> @@ -120,14 +120,20 @@ static int cmd_quota_rescan(int argc, char **argv)
>  	int wait_for_completion = 0;
>  
>  	while (1) {
> -		int c = getopt(argc, argv, "sw");
> +		int c = getopt(argc, argv, "swW");
>  		if (c < 0)
>  			break;
>  		switch (c) {
>  		case 's':
>  			ioctlnum = BTRFS_IOC_QUOTA_RESCAN_STATUS;
>  			break;
> +		case 'W':
> +			ioctlnum = 0;
> +			wait_for_completion = 1;
> +			break;
>  		case 'w':
> +			/* Reset it in case the user did both -W and -w */
> +			ioctlnum = BTRFS_IOC_QUOTA_RESCAN;
>  			wait_for_completion = 1;
>  			break;
>  		default:
> @@ -135,8 +141,9 @@ static int cmd_quota_rescan(int argc, char **argv)
>  		}
>  	}
>  
> -	if (ioctlnum != BTRFS_IOC_QUOTA_RESCAN && wait_for_completion) {
> -		error("switch -w cannot be used with -s");
> +	if (ioctlnum == BTRFS_IOC_QUOTA_RESCAN_STATUS && wait_for_completion) {
> +		error("switch -%c cannot be used with -s",
> +		      ioctlnum ? 'w' : 'W');

You can't really distinguish between w/W in this context, since ioctlnum
will be RESCAN_STATUS. So just harcode the w/W in the text message itself?

>  		return 1;
>  	}
>  
> @@ -150,8 +157,10 @@ static int cmd_quota_rescan(int argc, char **argv)
>  	if (fd < 0)
>  		return 1;
>  
> -	ret = ioctl(fd, ioctlnum, &args);
> -	e = errno;
> +	if (ioctlnum) {
> +		ret = ioctl(fd, ioctlnum, &args);
> +		e = errno;
> +	}
>  
>  	if (ioctlnum == BTRFS_IOC_QUOTA_RESCAN_STATUS) {
>  		close_file_or_dir(fd, dirstream);
> @@ -167,7 +176,7 @@ static int cmd_quota_rescan(int argc, char **argv)
>  		return 0;
>  	}
>  
> -	if (ret == 0) {
> +	if (ioctlnum == BTRFS_IOC_QUOTA_RESCAN && ret == 0) {
>  		printf("quota rescan started\n");
>  		fflush(stdout);
>  	} else if (ret < 0 && (!wait_for_completion || e != EINPROGRESS)) {
>