Re: [PATCH] btrfs-progs: fix dev stats error output related to replace handle

[Gui Hecheng <guihc.fnst@cn.fujitsu.com>]

On Wed, 2014-10-29 at 18:56 +0800, Anand Jain wrote:
> Hi Gui,
> 
>   We don't need this patch. Actually you should back out this patch to
>   get this correct.
> 
> [PATCH] btrfs-progs: do a separate probe for _transient_ replacing device
> 
>   OR apply. this
> 
> [PATCH] revert btrfs-progs: do a separate probe for _transient_ 
> replacing device
> 
>   Try it out. Lets know.
> 
> Thanks

Oh, yes, I've tried your revert patch and I acknowledge that it fixes
the problem.

So please *ignore* my patch David, sorry for the noise.

-Gui
> 
> 
> 
> On 10/23/14 09:56, Gui Hecheng wrote:
> > Steps to reproduce:
> > 	# mkfs.btrfs -f /dev/sdb7
> > 	# mount /dev/sdb7 /mnt
> > 	# btrfs dev stats /dev/sdb7
> > output:
> > 	[/dev/sdb7].write_io_errs   0
> > 	[/dev/sdb7].read_io_errs    0
> > 	[/dev/sdb7].flush_io_errs   0
> > 	[/dev/sdb7].corruption_errs 0
> > 	[/dev/sdb7].generation_errs 0
> > 	* ERROR: ioctl(BTRFS_IOC_GET_DEV_STATS) on  failed: No such device
> >
> > while the following cmd:
> > 	# btrfs dev stats /mnt
> > yields the right thing:
> > 	[/dev/sdb7].write_io_errs   0
> > 	[/dev/sdb7].read_io_errs    0
> > 	[/dev/sdb7].flush_io_errs   0
> > 	[/dev/sdb7].corruption_errs 0
> > 	[/dev/sdb7].generation_errs 0
> >
> > This is caused by commit:
> > 	commit d0588bfa479409b2a0f6243f894338a01a56221a
> > 	btrfs-progs: do a separate probe for transient replacing device
> >
> > The above commit trys to handle the fi show problem with device under
> > replacing, but it changes the @get_fs_info() logic which annoys dev stats.
> > For @get_fs_info():
> > o If the passed in @path is a mount point, then the @get_device_info() to
> >    probe the replacing device will be glad to accept the device index
> >    var @i as its init value 0 and the following i++ correctly sets @i
> >    to 1 as the start of all devices in btrfs.
> > o If @path is a block device, then the problem comes...
> >    The device index @i is set to devid of the block device passed in,
> >    and the @get_device_info() will be forced to accept the devid unwillingly.
> >    Then the following i++ do the evil of skip the block device desired and an
> >    empty piece is handled next which causes the ERROR above.
> >
> > To fix this problem, let's just pass 0 to the @get_device_info() explicitly,
> > and set the index @i to 1 if a mount point is passed in.
> >
> > Under my own test, this will not affect the original fix of the fi show
> > problem with device under replacing.
> >
> > Signed-off-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com>
> > ---
> >   utils.c | 7 +++++--
> >   1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/utils.c b/utils.c
> > index f10c178..0ba2b26 100644
> > --- a/utils.c
> > +++ b/utils.c
> > @@ -1881,12 +1881,15 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
> >   	}
> >
> >   	/* get the replace target device if it is there */
> > -	ret = get_device_info(fd, i, &di_args[ndevs]);
> > +	ret = get_device_info(fd, 0, &di_args[ndevs]);
> >   	if (!ret) {
> >   		ndevs++;
> >   		fi_args->num_devices++;
> >   	}
> > -	i++;
> > +
> > +	/* if a mount point is passed in, start from devid 1 */
> > +	if (fi_args->num_devices != 1)
> > +		i = 1;
> >
> >   	for (; i <= fi_args->max_id; ++i) {
> >   		BUG_ON(ndevs >= fi_args->num_devices);
> >