MFC r328224: MFV r328220: 8677 Open-Context Channel Programs

illumos/illumos-gate@a3b2868063897ff0083dea538f55f9873eec981f

https://www.illumos.org/issues/8677
  We want to be able to run channel programs outside of synching context.
  This would greatly improve performance of channel program that just gather
  information, as we won't have to wait for synching context anymore.

  This feature should introduce the following:
  - A new command line flag in "zfs program" to specify our intention to
  run in open context.
  - A new flag/option within the channel program ioctl which selects the
  context.
  - Appropriate error handling whenever we try a channel program in
  open-context that contains zfs.sync* expressions.
  - Documentation for the new feature in the manual pages.

Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Chris Williamson <chris.williamson@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Serapheim Dimitropoulos <serapheim@delphix.com>

1 files changed, 40 insertions, 11 deletions

diff --git a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
index ec32486..6766083 100644
--- a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
+++ b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
@@ -918,6 +918,25 @@ lzc_destroy_bookmarks(nvlist_t *bmarks, nvlist_t **errlist)
 	return (error);
 }
 
+static int
+lzc_channel_program_impl(const char *pool, const char *program, boolean_t sync,
+    uint64_t instrlimit, uint64_t memlimit, nvlist_t *argnvl, nvlist_t **outnvl)
+{
+	int error;
+	nvlist_t *args;
+
+	args = fnvlist_alloc();
+	fnvlist_add_string(args, ZCP_ARG_PROGRAM, program);
+	fnvlist_add_nvlist(args, ZCP_ARG_ARGLIST, argnvl);
+	fnvlist_add_boolean_value(args, ZCP_ARG_SYNC, sync);
+	fnvlist_add_uint64(args, ZCP_ARG_INSTRLIMIT, instrlimit);
+	fnvlist_add_uint64(args, ZCP_ARG_MEMLIMIT, memlimit);
+	error = lzc_ioctl(ZFS_IOC_CHANNEL_PROGRAM, pool, args, outnvl);
+	fnvlist_free(args);
+
+	return (error);
+}
+
 /*
  * Executes a channel program.
  *
@@ -955,16 +974,26 @@ int
 lzc_channel_program(const char *pool, const char *program, uint64_t instrlimit,
     uint64_t memlimit, nvlist_t *argnvl, nvlist_t **outnvl)
 {
-	int error;
-	nvlist_t *args;
-
-	args = fnvlist_alloc();
-	fnvlist_add_string(args, ZCP_ARG_PROGRAM, program);
-	fnvlist_add_nvlist(args, ZCP_ARG_ARGLIST, argnvl);
-	fnvlist_add_uint64(args, ZCP_ARG_INSTRLIMIT, instrlimit);
-	fnvlist_add_uint64(args, ZCP_ARG_MEMLIMIT, memlimit);
-	error = lzc_ioctl(ZFS_IOC_CHANNEL_PROGRAM, pool, args, outnvl);
-	fnvlist_free(args);
+	return (lzc_channel_program_impl(pool, program, B_TRUE, instrlimit,
+	    memlimit, argnvl, outnvl));
+}
 
-	return (error);
+/*
+ * Executes a read-only channel program.
+ *
+ * A read-only channel program works programmatically the same way as a
+ * normal channel program executed with lzc_channel_program(). The only
+ * difference is it runs exclusively in open-context and therefore can
+ * return faster. The downside to that, is that the program cannot change
+ * on-disk state by calling functions from the zfs.sync submodule.
+ *
+ * The return values of this function (and their meaning) are exactly the
+ * same as the ones described in lzc_channel_program().
+ */
+int
+lzc_channel_program_nosync(const char *pool, const char *program,
+    uint64_t timeout, uint64_t memlimit, nvlist_t *argnvl, nvlist_t **outnvl)
+{
+	return (lzc_channel_program_impl(pool, program, B_FALSE, timeout,
+	    memlimit, argnvl, outnvl));
 }