| From foo@baz Sun May 27 17:33:38 CEST 2018 |
| From: mulhern <amulhern@redhat.com> |
| Date: Mon, 27 Nov 2017 10:02:39 -0500 |
| Subject: dm thin: fix documentation relative to low water mark threshold |
| |
| From: mulhern <amulhern@redhat.com> |
| |
| [ Upstream commit 9b28a1102efc75d81298198166ead87d643a29ce ] |
| |
| Fixes: |
| 1. The use of "exceeds" when the opposite of exceeds, falls below, |
| was meant. |
| 2. Properly speaking, a table can not exceed a threshold. |
| |
| It emphasizes the important point, which is that it is the userspace |
| daemon's responsibility to check for low free space when a device |
| is resumed, since it won't get a special event indicating low free |
| space in that situation. |
| |
| Signed-off-by: mulhern <amulhern@redhat.com> |
| Signed-off-by: Mike Snitzer <snitzer@redhat.com> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| Documentation/device-mapper/thin-provisioning.txt | 8 +++++--- |
| 1 file changed, 5 insertions(+), 3 deletions(-) |
| |
| --- a/Documentation/device-mapper/thin-provisioning.txt |
| +++ b/Documentation/device-mapper/thin-provisioning.txt |
| @@ -112,9 +112,11 @@ $low_water_mark is expressed in blocks o |
| free space on the data device drops below this level then a dm event |
| will be triggered which a userspace daemon should catch allowing it to |
| extend the pool device. Only one such event will be sent. |
| -Resuming a device with a new table itself triggers an event so the |
| -userspace daemon can use this to detect a situation where a new table |
| -already exceeds the threshold. |
| + |
| +No special event is triggered if a just resumed device's free space is below |
| +the low water mark. However, resuming a device always triggers an |
| +event; a userspace daemon should verify that free space exceeds the low |
| +water mark when handling this event. |
| |
| A low water mark for the metadata device is maintained in the kernel and |
| will trigger a dm event if free space on the metadata device drops below |