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authormulhern <amulhern@redhat.com>2017-11-27 18:02:39 +0300
committerMike Snitzer <snitzer@redhat.com>2018-01-17 17:16:10 +0300
commit9b28a1102efc75d81298198166ead87d643a29ce (patch)
tree68d764d3f4181bf41f3570775c8706ced97059e1 /Documentation/device-mapper
parent1346638e5f80588dfafbf07315f72b84c2ab1113 (diff)
downloadlinux-9b28a1102efc75d81298198166ead87d643a29ce.tar.xz
dm thin: fix documentation relative to low water mark threshold
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>
Diffstat (limited to 'Documentation/device-mapper')
-rw-r--r--Documentation/device-mapper/thin-provisioning.txt8
1 files changed, 5 insertions, 3 deletions
diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt
index 1699a55b7b70..ef639960b272 100644
--- 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 of size $data_block_size. If
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