diff mbox series

[10/36] xfs_scrub_all: walk the lsblk device/fs hierarchy correctly

Message ID 155259749135.31886.17642733861513368966.stgit@magnolia (mailing list archive)
State Accepted, archived
Headers show
Series xfsprogs-5.0: fix various problems | expand

Commit Message

Darrick J. Wong March 14, 2019, 9:04 p.m. UTC
From: Darrick J. Wong <darrick.wong@oracle.com>

Back when I was designing xfs_scrub_all, I naïvely assumed that the
emitted output would always list physical storage before the virtual
devices stacked atop it.  However, this is not actually true when one
omits the "NAME" column, which is crucial to forcing the output (json or
otherwise) to capture the block device hierarchy.  If the assumption is
violated, the program crashes with a python exception.

To fix this, force the hierarchal json output and restructure the
discovery routines to walk the json object that we receive, from the top
(physical devices) downwards to wherever there are live xfs filesystems.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 scrub/xfs_scrub_all.in |   28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

Comments

Eric Sandeen March 15, 2019, 2:46 a.m. UTC | #1
On 3/14/19 4:04 PM, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Back when I was designing xfs_scrub_all, I naïvely assumed that the
> emitted output would always list physical storage before the virtual
> devices stacked atop it.  However, this is not actually true when one
> omits the "NAME" column,

I think I asked this on IRC but for the record, is this incidental
or guaranteed by lsblk?  I don't see this distinction in the manpage.

I worry about depending on undocumented behavior...

Looking back through IRC, I think we shrugged over this, I asked kzak
but didn't get a reply, will try to find him again.

(also FWIW, older lsblk rejects -J, do we care?)

-Eric

> which is crucial to forcing the output (json or
> otherwise) to capture the block device hierarchy.  If the assumption is
> violated, the program crashes with a python exception.
> 
> To fix this, force the hierarchal json output and restructure the
> discovery routines to walk the json object that we receive, from the top
> (physical devices) downwards to wherever there are live xfs filesystems.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  scrub/xfs_scrub_all.in |   28 +++++++++++++++++-----------
>  1 file changed, 17 insertions(+), 11 deletions(-)
> 
> 
> diff --git a/scrub/xfs_scrub_all.in b/scrub/xfs_scrub_all.in
> index c4e9899d..5b76b49a 100644
> --- a/scrub/xfs_scrub_all.in
> +++ b/scrub/xfs_scrub_all.in
> @@ -28,9 +28,21 @@ def DEVNULL():
>  
>  def find_mounts():
>  	'''Map mountpoints to physical disks.'''
> +	def find_xfs_mounts(bdev, fs, lastdisk):
> +		'''Attach lastdisk to each fs found under bdev.'''
> +		if bdev['fstype'] == 'xfs' and bdev['mountpoint'] is not None:
> +			mnt = bdev['mountpoint']
> +			if mnt in fs:
> +				fs[mnt].add(lastdisk)
> +			else:
> +				fs[mnt] = set([lastdisk])
> +		if 'children' not in bdev:
> +			return
> +		for child in bdev['children']:
> +			find_xfs_mounts(child, fs, lastdisk)
>  
>  	fs = {}
> -	cmd=['lsblk', '-o', 'KNAME,TYPE,FSTYPE,MOUNTPOINT', '-J']
> +	cmd=['lsblk', '-o', 'NAME,KNAME,TYPE,FSTYPE,MOUNTPOINT', '-J']
>  	result = subprocess.Popen(cmd, stdout=subprocess.PIPE)
>  	result.wait()
>  	if result.returncode != 0:
> @@ -38,18 +50,12 @@ def find_mounts():
>  	sarray = [x.decode(sys.stdout.encoding) for x in result.stdout.readlines()]
>  	output = ' '.join(sarray)
>  	bdevdata = json.loads(output)
> +
>  	# The lsblk output had better be in disks-then-partitions order
>  	for bdev in bdevdata['blockdevices']:
> -		if bdev['type'] in ('disk', 'loop'):
> -			lastdisk = bdev['kname']
> -		if bdev['fstype'] == 'xfs':
> -			mnt = bdev['mountpoint']
> -			if mnt is None:
> -				continue
> -			if mnt in fs:
> -				fs[mnt].add(lastdisk)
> -			else:
> -				fs[mnt] = set([lastdisk])
> +		lastdisk = bdev['kname']
> +		find_xfs_mounts(bdev, fs, lastdisk)
> +
>  	return fs
>  
>  def kill_systemd(unit, proc):
>
Darrick J. Wong March 15, 2019, 2:55 a.m. UTC | #2
On Thu, Mar 14, 2019 at 09:46:26PM -0500, Eric Sandeen wrote:
> On 3/14/19 4:04 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Back when I was designing xfs_scrub_all, I naïvely assumed that the
> > emitted output would always list physical storage before the virtual
> > devices stacked atop it.  However, this is not actually true when one
> > omits the "NAME" column,
> 
> I think I asked this on IRC but for the record, is this incidental
> or guaranteed by lsblk?  I don't see this distinction in the manpage.

Incidental.

> I worry about depending on undocumented behavior...
> 
> Looking back through IRC, I think we shrugged over this, I asked kzak
> but didn't get a reply, will try to find him again.

We did shrug about this.

> (also FWIW, older lsblk rejects -J, do we care?)

No, because xfs_scrub_all will just exit if lsblk returns nonzero.

--D

> -Eric
> 
> > which is crucial to forcing the output (json or
> > otherwise) to capture the block device hierarchy.  If the assumption is
> > violated, the program crashes with a python exception.
> > 
> > To fix this, force the hierarchal json output and restructure the
> > discovery routines to walk the json object that we receive, from the top
> > (physical devices) downwards to wherever there are live xfs filesystems.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  scrub/xfs_scrub_all.in |   28 +++++++++++++++++-----------
> >  1 file changed, 17 insertions(+), 11 deletions(-)
> > 
> > 
> > diff --git a/scrub/xfs_scrub_all.in b/scrub/xfs_scrub_all.in
> > index c4e9899d..5b76b49a 100644
> > --- a/scrub/xfs_scrub_all.in
> > +++ b/scrub/xfs_scrub_all.in
> > @@ -28,9 +28,21 @@ def DEVNULL():
> >  
> >  def find_mounts():
> >  	'''Map mountpoints to physical disks.'''
> > +	def find_xfs_mounts(bdev, fs, lastdisk):
> > +		'''Attach lastdisk to each fs found under bdev.'''
> > +		if bdev['fstype'] == 'xfs' and bdev['mountpoint'] is not None:
> > +			mnt = bdev['mountpoint']
> > +			if mnt in fs:
> > +				fs[mnt].add(lastdisk)
> > +			else:
> > +				fs[mnt] = set([lastdisk])
> > +		if 'children' not in bdev:
> > +			return
> > +		for child in bdev['children']:
> > +			find_xfs_mounts(child, fs, lastdisk)
> >  
> >  	fs = {}
> > -	cmd=['lsblk', '-o', 'KNAME,TYPE,FSTYPE,MOUNTPOINT', '-J']
> > +	cmd=['lsblk', '-o', 'NAME,KNAME,TYPE,FSTYPE,MOUNTPOINT', '-J']
> >  	result = subprocess.Popen(cmd, stdout=subprocess.PIPE)
> >  	result.wait()
> >  	if result.returncode != 0:
> > @@ -38,18 +50,12 @@ def find_mounts():
> >  	sarray = [x.decode(sys.stdout.encoding) for x in result.stdout.readlines()]
> >  	output = ' '.join(sarray)
> >  	bdevdata = json.loads(output)
> > +
> >  	# The lsblk output had better be in disks-then-partitions order
> >  	for bdev in bdevdata['blockdevices']:
> > -		if bdev['type'] in ('disk', 'loop'):
> > -			lastdisk = bdev['kname']
> > -		if bdev['fstype'] == 'xfs':
> > -			mnt = bdev['mountpoint']
> > -			if mnt is None:
> > -				continue
> > -			if mnt in fs:
> > -				fs[mnt].add(lastdisk)
> > -			else:
> > -				fs[mnt] = set([lastdisk])
> > +		lastdisk = bdev['kname']
> > +		find_xfs_mounts(bdev, fs, lastdisk)
> > +
> >  	return fs
> >  
> >  def kill_systemd(unit, proc):
> >
diff mbox series

Patch

diff --git a/scrub/xfs_scrub_all.in b/scrub/xfs_scrub_all.in
index c4e9899d..5b76b49a 100644
--- a/scrub/xfs_scrub_all.in
+++ b/scrub/xfs_scrub_all.in
@@ -28,9 +28,21 @@  def DEVNULL():
 
 def find_mounts():
 	'''Map mountpoints to physical disks.'''
+	def find_xfs_mounts(bdev, fs, lastdisk):
+		'''Attach lastdisk to each fs found under bdev.'''
+		if bdev['fstype'] == 'xfs' and bdev['mountpoint'] is not None:
+			mnt = bdev['mountpoint']
+			if mnt in fs:
+				fs[mnt].add(lastdisk)
+			else:
+				fs[mnt] = set([lastdisk])
+		if 'children' not in bdev:
+			return
+		for child in bdev['children']:
+			find_xfs_mounts(child, fs, lastdisk)
 
 	fs = {}
-	cmd=['lsblk', '-o', 'KNAME,TYPE,FSTYPE,MOUNTPOINT', '-J']
+	cmd=['lsblk', '-o', 'NAME,KNAME,TYPE,FSTYPE,MOUNTPOINT', '-J']
 	result = subprocess.Popen(cmd, stdout=subprocess.PIPE)
 	result.wait()
 	if result.returncode != 0:
@@ -38,18 +50,12 @@  def find_mounts():
 	sarray = [x.decode(sys.stdout.encoding) for x in result.stdout.readlines()]
 	output = ' '.join(sarray)
 	bdevdata = json.loads(output)
+
 	# The lsblk output had better be in disks-then-partitions order
 	for bdev in bdevdata['blockdevices']:
-		if bdev['type'] in ('disk', 'loop'):
-			lastdisk = bdev['kname']
-		if bdev['fstype'] == 'xfs':
-			mnt = bdev['mountpoint']
-			if mnt is None:
-				continue
-			if mnt in fs:
-				fs[mnt].add(lastdisk)
-			else:
-				fs[mnt] = set([lastdisk])
+		lastdisk = bdev['kname']
+		find_xfs_mounts(bdev, fs, lastdisk)
+
 	return fs
 
 def kill_systemd(unit, proc):