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Subject[PATCH AUTOSEL for 4.4 116/162] dm thin: fix documentation relative to low water mark threshold
From: mulhern <>

[ Upstream commit 9b28a1102efc75d81298198166ead87d643a29ce ]

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 <>
Signed-off-by: Mike Snitzer <>
Signed-off-by: Sasha Levin <>
Documentation/device-mapper/thin-provisioning.txt | 8 +++++---
1 file 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
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