dm: documentation fix
Subsystems (2)
PATCH 1/7 dm: documentation fix
From: mulhern <[email protected]>
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 <[email protected]>
--- Documentation/device-mapper/thin-provisioning.txt | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
Documentation/device-mapper/thin-provisioning.txt +5 -3
@@ -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
Signature · 1 line
2.9.5
PATCH 2/7 dm: documentation fix
From: mulhern <[email protected]>
Use possessive pronoun where appropriate
Instead of contraction.
Signed-off-by mulhern <[email protected]>
--- Documentation/device-mapper/cache-policies.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
Documentation/device-mapper/cache-policies.txt +2 -2
@@ -60,7 +60,7 @@ Memory usage: The mq policy used a lot of memory; 88 bytes per cache block on a 64 bit machine. -smq uses 28bit indexes to implement it's data structures rather than +smq uses 28bit indexes to implement its data structures rather than pointers. It avoids storing an explicit hit count for each block. It has a 'hotspot' queue, rather than a pre-cache, which uses a quarter of the entries (each hotspot block covers a larger area than a single
@@ -84,7 +84,7 @@ resulting in better promotion/demotion decisions. Adaptability: The mq policy maintained a hit count for each cache block. For a -different block to get promoted to the cache it's hit count has to +different block to get promoted to the cache its hit count has to exceed the lowest currently in the cache. This meant it could take a long time for the cache to adapt between varying IO patterns.
Signature · 1 line
2.9.5
PATCH 3/7 dm: documentation fix
In reply to [email protected]From: mulhern <[email protected]>
Delete obsoleted paragraph
The 'mq' policy is no longer the default policy, and the default policy, 'smq', does not store hit counts.
Signed-off-by mulhern <[email protected]>
--- Documentation/device-mapper/cache.txt | 5 ----- 1 file changed, 5 deletions(-)
Documentation/device-mapper/cache.txt +0 -5
@@ -143,11 +143,6 @@ the policy how big this chunk is, but it should be kept small. Like the dirty flags this data is lost if there's a crash so a safe fallback value should always be possible. -For instance, the 'mq' policy, which is currently the default policy, -uses this facility to store the hit count of the cache blocks. If -there's a crash this information will be lost, which means the cache -may be less efficient until those hit counts are regenerated. - Policy hints affect performance, not correctness. Policy messaging
Signature · 1 line
2.9.5
PATCH 4/7 dm: documentation fix
In reply to [email protected]From: mulhern <[email protected]>
Be consistent in specifying sectors and SI units
Signed-off-by mulhern <[email protected]>
--- Documentation/device-mapper/cache.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
Documentation/device-mapper/cache.txt +2 -2
@@ -59,7 +59,7 @@ Fixed block size The origin is divided up into blocks of a fixed size. This block size is configurable when you first create the cache. Typically we've been using block sizes of 256KB - 1024KB. The block size must be between 64 -(32KB) and 2097152 (1GB) and a multiple of 64 (32KB). +sectors (32KB) and 2097152 sectors (1GB) and a multiple of 64 sectors (32KB). Having a fixed block size simplifies the target a lot. But it is something of a compromise. For instance, a small part of a block may be
@@ -119,7 +119,7 @@ doing here to avoid migrating during those peak io moments. For the time being, a message "migration_threshold <#sectors>" can be used to set the maximum number of sectors being migrated, -the default being 204800 sectors (or 100MB). +the default being 204800 sectors (100MB). Updating on-disk metadata -------------------------
Signature · 1 line
2.9.5
PATCH 5/7 dm: documentation fix
In reply to [email protected]From: mulhern <[email protected]>
Add a remark about the representation of <highest mapped sector> when there is none.
Signed-off-by mulhern <[email protected]>
--- Documentation/device-mapper/thin-provisioning.txt | 3 +++ 1 file changed, 3 insertions(+)
Documentation/device-mapper/thin-provisioning.txt +3 -0
@@ -396,3 +396,6 @@ ii) Status If the pool has encountered device errors and failed, the status will just contain the string 'Fail'. The userspace recovery tools should then be used. + + In the case where <nr mapped sectors> is 0, there is no highest + mapped sector and the value of <highest mapped sector> is unspecified.
Signature · 1 line
2.9.5
PATCH 6/7 dm: documentation fix
In reply to [email protected]From: mulhern <[email protected]>
Make the format string for thinpool status more correct.
Swap the order of two items to correspond with reality.
Signed-off-by mulhern <[email protected]>
--- Documentation/device-mapper/thin-provisioning.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Documentation/device-mapper/thin-provisioning.txt +1 -1
@@ -276,7 +276,7 @@ ii) Status <transaction id> <used metadata blocks>/<total metadata blocks> <used data blocks>/<total data blocks> <held metadata root> - [no_]discard_passdown ro|rw + ro|rw|out_of_data_space [no_]discard_passdown transaction id: A 64-bit number used by userspace to help synchronise with metadata
Signature · 1 line
2.9.5
PATCH 7/7 dm: documentation fix
In reply to [email protected]From: mulhern <[email protected]>
Extend thinpool status format string with omitted fields.
Signed-off-by mulhern <[email protected]>
--- Documentation/device-mapper/thin-provisioning.txt | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
Documentation/device-mapper/thin-provisioning.txt +2 -1
@@ -276,7 +276,8 @@ ii) Status <transaction id> <used metadata blocks>/<total metadata blocks> <used data blocks>/<total data blocks> <held metadata root> - ro|rw|out_of_data_space [no_]discard_passdown + ro|rw|out_of_data_space [no_]discard_passdown [error|queue]_if_no_space + needs_check|- transaction id: A 64-bit number used by userspace to help synchronise with metadata
Signature · 1 line
2.9.5