[PATCH 08/11] xfs_scrub: fix media verification thread pool size calculations

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

The read verifier pool deals with two different thread counts -- there's
the submitter thread count that enables us to perform per-thread verify
request aggregation, and then there's the io thread pool count which is
the maximum number of IO requests we want to send to the disk at any
given time.

The io thread pool count should be derived from disk_heads() but instead
we bungle it by measuring and modifying(!) the nproc global variable.
Fix the derivation to use global variables correctly.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 scrub/read_verify.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)


diff --git a/scrub/read_verify.c b/scrub/read_verify.c
index bab8411a..c8e0f562 100644
--- a/scrub/read_verify.c
+++ b/scrub/read_verify.c
@@ -75,6 +75,7 @@ read_verify_pool_alloc(
 	struct read_verify_pool		**prvp)
 {
 	struct read_verify_pool		*rvp;
+	unsigned int			verifier_threads = disk_heads(disk);
 	int				ret;
 
 	/*
@@ -94,7 +95,7 @@ read_verify_pool_alloc(
 			RVP_IO_MAX_SIZE);
 	if (ret)
 		goto out_free;
-	ret = ptcounter_alloc(nproc, &rvp->verified_bytes);
+	ret = ptcounter_alloc(verifier_threads, &rvp->verified_bytes);
 	if (ret)
 		goto out_buf;
 	rvp->miniosz = miniosz;
@@ -106,11 +107,8 @@ read_verify_pool_alloc(
 			&rvp->rvstate);
 	if (ret)
 		goto out_counter;
-	/* Run in the main thread if we only want one thread. */
-	if (nproc == 1)
-		nproc = 0;
 	ret = workqueue_create(&rvp->wq, (struct xfs_mount *)rvp,
-			disk_heads(disk));
+			verifier_threads == 1 ? 0 : verifier_threads);
 	if (ret)
 		goto out_rvstate;
 	*prvp = rvp;