xfs_scrub: figure out how many threads we're going to need

Create the plumbing to figure out how many threads we're going to want
to do all of our scrubbing.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

3 files changed, 31 insertions, 0 deletions

diff --git a/scrub/common.c b/scrub/common.c
index 37ccd4a36e..05bb89b1de 100644
--- a/scrub/common.c
+++ b/scrub/common.c
@@ -168,3 +168,29 @@ no_prefix:
 	*units = "";
 	return number;
 }
+
+/* How many threads to kick off? */
+unsigned int
+scrub_nproc(
+	struct scrub_ctx	*ctx)
+{
+	if (nr_threads)
+		return nr_threads;
+	return ctx->nr_io_threads;
+}
+
+/*
+ * How many threads to kick off for a workqueue?  If we only want one
+ * thread, save ourselves the overhead and just run it in the main thread.
+ */
+unsigned int
+scrub_nproc_workqueue(
+	struct scrub_ctx	*ctx)
+{
+	unsigned int		x;
+
+	x = scrub_nproc(ctx);
+	if (x == 1)
+		x = 0;
+	return x;
+}
diff --git a/scrub/common.h b/scrub/common.h
index e26e0e849a..4779dbdc5c 100644
--- a/scrub/common.h
+++ b/scrub/common.h
@@ -61,5 +61,7 @@ debug_tweak_on(
 double timeval_subtract(struct timeval *tv1, struct timeval *tv2);
 double auto_space_units(unsigned long long kilobytes, char **units);
 double auto_units(unsigned long long number, char **units);
+unsigned int scrub_nproc(struct scrub_ctx *ctx);
+unsigned int scrub_nproc_workqueue(struct scrub_ctx *ctx);
 
 #endif /* XFS_SCRUB_COMMON_H_ */
diff --git a/scrub/xfs_scrub.h b/scrub/xfs_scrub.h
index 51b8b7a44d..6d9f0c1e2d 100644
--- a/scrub/xfs_scrub.h
+++ b/scrub/xfs_scrub.h
@@ -54,6 +54,9 @@ struct scrub_ctx {
 	/* How does the user want us to react to errors? */
 	enum error_action	error_action;
 
+	/* Number of threads for metadata scrubbing */
+	unsigned int		nr_io_threads;
+
 	/* Mutable scrub state; use lock. */
 	pthread_mutex_t		lock;
 	unsigned long long	max_errors;