* [PATCH] dm-cache: document zeroing metadata device step
@ 2020-07-12 19:40 Austin Chang
2020-07-12 19:59 ` Matthew Wilcox
0 siblings, 1 reply; 4+ messages in thread
From: Austin Chang @ 2020-07-12 19:40 UTC (permalink / raw)
To: dm-devel
Cc: Austin Chang, Alasdair Kergon, Mike Snitzer, Jonathan Corbet,
linux-doc, linux-kernel
Inform dmsetup users to zero the first 4k of the metadata device at
cache creation in examples, just as mentioned in thin-provisioning
documentation. Instructions to use lvmcache for end users may be added
as well.
Link: https://www.redhat.com/archives/dm-devel/2013-April/msg00124.html
Signed-off-by: Austin Chang <austin880625@gmail.com>
---
Documentation/admin-guide/device-mapper/cache.rst | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/Documentation/admin-guide/device-mapper/cache.rst b/Documentation/admin-guide/device-mapper/cache.rst
index f15e5254d05b..ef9a82d50d19 100644
--- a/Documentation/admin-guide/device-mapper/cache.rst
+++ b/Documentation/admin-guide/device-mapper/cache.rst
@@ -330,6 +330,10 @@ https://github.com/jthornber/device-mapper-test-suite
::
+ # When using dmsetup directly instead of volume manager like lvm2,
+ # the first 4k of the metadata device should be zeroed to indicate
+ # empty metadata.
+ dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc
dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
/dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0'
dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] dm-cache: document zeroing metadata device step
2020-07-12 19:40 [PATCH] dm-cache: document zeroing metadata device step Austin Chang
@ 2020-07-12 19:59 ` Matthew Wilcox
2020-07-12 21:10 ` Austin Chang
0 siblings, 1 reply; 4+ messages in thread
From: Matthew Wilcox @ 2020-07-12 19:59 UTC (permalink / raw)
To: Austin Chang
Cc: dm-devel, Alasdair Kergon, Mike Snitzer, Jonathan Corbet,
linux-doc, linux-kernel
On Mon, Jul 13, 2020 at 03:40:39AM +0800, Austin Chang wrote:
> + # When using dmsetup directly instead of volume manager like lvm2,
> + # the first 4k of the metadata device should be zeroed to indicate
> + # empty metadata.
> + dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc
... don't you need 'count=1' or you'll zero the entire device?
> dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
> /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0'
> dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
> --
> 2.26.2
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] dm-cache: document zeroing metadata device step
2020-07-12 19:59 ` Matthew Wilcox
@ 2020-07-12 21:10 ` Austin Chang
2020-07-12 21:47 ` [PATCH v2] " Austin Chang
0 siblings, 1 reply; 4+ messages in thread
From: Austin Chang @ 2020-07-12 21:10 UTC (permalink / raw)
To: Matthew Wilcox
Cc: dm-devel, Alasdair Kergon, Mike Snitzer, Jonathan Corbet,
linux-doc, linux-kernel
On Sun, Jul 12, 2020 at 08:59:32PM +0100, Matthew Wilcox wrote:
> On Mon, Jul 13, 2020 at 03:40:39AM +0800, Austin Chang wrote:
> > + # When using dmsetup directly instead of volume manager like lvm2,
> > + # the first 4k of the metadata device should be zeroed to indicate
> > + # empty metadata.
> > + dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc
>
> ... don't you need 'count=1' or you'll zero the entire device?
Oops, I copied the command I just used since zeroing the whole metadata
device didn't harm. But 'count=1' should match what I've just written.
I will send a v2 patch later
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] dm-cache: document zeroing metadata device step
2020-07-12 21:10 ` Austin Chang
@ 2020-07-12 21:47 ` Austin Chang
0 siblings, 0 replies; 4+ messages in thread
From: Austin Chang @ 2020-07-12 21:47 UTC (permalink / raw)
To: dm-devel
Cc: Austin Chang, Alasdair Kergon, Mike Snitzer, Jonathan Corbet,
linux-doc, linux-kernel
Inform dmsetup users to zero the first 4k of the metadata device at
cache creation in examples, just as mentioned in thin-provisioning
documentation. Instructions to use lvmcache for end users may be added
as well.
Link: https://www.redhat.com/archives/dm-devel/2013-April/msg00124.html
Signed-off-by: Austin Chang <austin880625@gmail.com>
---
Changes in v2:
- Correct the dd arguments
Documentation/admin-guide/device-mapper/cache.rst | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/Documentation/admin-guide/device-mapper/cache.rst b/Documentation/admin-guide/device-mapper/cache.rst
index f15e5254d05b..16a1c96946a6 100644
--- a/Documentation/admin-guide/device-mapper/cache.rst
+++ b/Documentation/admin-guide/device-mapper/cache.rst
@@ -330,6 +330,10 @@ https://github.com/jthornber/device-mapper-test-suite
::
+ # When using dmsetup directly instead of volume manager like lvm2,
+ # the first 4k of the metadata device should be zeroed to indicate
+ # empty metadata.
+ dd if=/dev/zero of=/dev/mapper/metadata bs=4k count=1
dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
/dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0'
dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-07-12 21:51 UTC | newest]
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2020-07-12 19:40 [PATCH] dm-cache: document zeroing metadata device step Austin Chang
2020-07-12 19:59 ` Matthew Wilcox
2020-07-12 21:10 ` Austin Chang
2020-07-12 21:47 ` [PATCH v2] " Austin Chang
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