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

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

On Wed, Mar 18, 2020 at 06:56:51PM +0800, Qu Wenruo wrote:
> 
> 
> On 2020/3/8 上午6:45, Marcos Paulo de Souza wrote:
> > 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>.
> 
> Resizes "to its max size".
> 
> >  
> >  *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>",
> 
> Same here, resize to its max size.
> 
> >  	"-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;
> > +	}
> > +
> 
> I'm pretty happy since it's all done in user space.
> 
> But this is a different error, here we succeeded in replace, but only
> failed in resize (which should be pretty rare to hit though).
> 
> We should provide some better error message for it other than just error
> out.

Function resize_filesystem already checks for errors, and it even print's a
resize message before calling the resize ioctl. Or do you mean another message
specifying that "replace finished, but resize failed" along the messages already
being provided by resize_filesystem function?

Thanks,
  Marcos

> 
> Thanks,
> Qu
> 
> >  	close_file_or_dir(fdmnt, dirstream);
> >  	return 0;
> >  
> > 
>