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throttle: Use bs->throttle_state instead of bs->io_limits_enabled

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There are two ways to check for I/O limits in a BlockDriverState:

- bs->throttle_state: if this pointer is not NULL, it means that this
  BDS is member of a throttling group, its ThrottleTimers structure
  has been initialized and its I/O limits are ready to be applied.

- bs->io_limits_enabled: if true it means that the throttle_state
  pointer is valid _and_ the limits are currently enabled.

The latter is used in several places to check whether a BDS has I/O
limits configured, but what it really checks is whether requests
are being throttled or not. For example, io_limits_enabled can be
temporarily set to false in cases like bdrv_read_unthrottled() without
otherwise touching the throtting configuration of that BDS.

This patch replaces bs->io_limits_enabled with bs->throttle_state in
all cases where what we really want to check is the existence of I/O
limits, not whether they are currently enabled or not.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Alberto Garcia 2015-11-04 15:15:36 +02:00 • committed by Kevin Wolf
parent 5ac724184c
commit a0d64a61db
4 changed files with 10 additions and 7 deletions
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5
include/block/block_int.h
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@ -390,7 +390,10 @@ struct BlockDriverState {
/* number of in-flight serialising requests */
unsigned int serialising_in_flight;
/* I/O throttling */
/* I/O throttling.
* throttle_state tells us if this BDS has I/O limits configured.
* io_limits_enabled tells us if they are currently being
* enforced, but it can be temporarily set to false */
CoQueue throttled_reqs[2];
bool io_limits_enabled;
/* The following fields are protected by the ThrottleGroup lock.