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Fix __zio_execute() asynchronous dispatch 

To save valuable stack all zio's were made asynchronous when in the
tgx_sync_thread context or during pool initialization.  See commit
2fac4c2 for the original patch and motivation.

Unfortuantely, the changes to dsl_pool_sync_context() made by the
feature flags broke this logic causing in __zio_execute() to dispatch
itself infinitely when called during pool initialization.  This
commit refines the existing logic to specificly target only the two
cases we care about.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf 2012-12-17 16:23:27 -08:00
parent ea0b2538cd
commit 91579709fc
1 changed files with 17 additions and 9 deletions
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26
module/zfs/zio.c
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@ -1248,7 +1248,7 @@ __zio_execute(zio_t *zio)
while (zio->io_stage < ZIO_STAGE_DONE) {
enum zio_stage pipeline = zio->io_pipeline;
enum zio_stage stage = zio->io_stage;
dsl_pool_t *dsl;
dsl_pool_t *dp;
boolean_t cut;
int rv;
@ -1262,7 +1262,7 @@ __zio_execute(zio_t *zio)
ASSERT(stage <= ZIO_STAGE_DONE);
dsl = spa_get_dsl(zio->io_spa);
dp = spa_get_dsl(zio->io_spa);
cut = (stage == ZIO_STAGE_VDEV_IO_START) ?
zio_requeue_io_start_cut_in_line : B_FALSE;
@ -1272,16 +1272,24 @@ __zio_execute(zio_t *zio)
* or may wait for an I/O that needs an interrupt thread
* to complete, issue async to avoid deadlock.
*
* If we are in the txg_sync_thread or being called
* during pool init issue async to minimize stack depth.
* Both of these call paths may be recursively called.
*
* For VDEV_IO_START, we cut in line so that the io will
* be sent to disk promptly.
*/
if (((stage & ZIO_BLOCKING_STAGES) && zio->io_vd == NULL &&
zio_taskq_member(zio, ZIO_TASKQ_INTERRUPT)) ||
(dsl != NULL && dsl_pool_sync_context(dsl))) {
if ((stage & ZIO_BLOCKING_STAGES) && zio->io_vd == NULL &&
zio_taskq_member(zio, ZIO_TASKQ_INTERRUPT)) {
zio_taskq_dispatch(zio, ZIO_TASKQ_ISSUE, cut);
return;
}
/*
* If we executing in the context of the tx_sync_thread,
* or we are performing pool initialization outside of a
* zio_taskq[ZIO_TASKQ_ISSUE] context. Then issue the zio
* async to minimize stack usage for these deep call paths.
*/
if ((dp && curthread == dp->dp_tx.tx_sync_thread) ||
(dp && spa_is_initializing(dp->dp_spa) &&
!zio_taskq_member(zio, ZIO_TASKQ_ISSUE))) {
zio_taskq_dispatch(zio, ZIO_TASKQ_ISSUE, cut);
return;
}