Support re-adding of old devices when assembling an array.

From: NeilBrown <neilb@suse.de>

When we assemble an array, either with -A or -I, it is possible
that the kernel will reject some devices because they have
old event counts.
If the 'action=re-add' policy is in effect, we want to add
those devices anyway on the assumption that they were only
missing due to a cabling problem, and it has been fixed.

So after starting the array, attempt to add each device again.
Any that are members of the array will failed with -EBUSY.
Others might succeed if the kernel is happy enough with them.

Also disable the re-adding of devices to an active array
with -I, unless 'action=re-add' is in effect.  That behaviour is
inconsistent with --assemble.

Signed-off-by: NeilBrown <neilb@suse.de
---
 Assemble.c    |   19 +++++++++++++++++++
 Incremental.c |   26 ++++++++++++++++++++++++--
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/Assemble.c b/Assemble.c
index 703b122..793be29 100644
--- a/Assemble.c
+++ b/Assemble.c
@@ -1143,6 +1143,25 @@ int Assemble(struct supertype *st, char *mddev,
 								      (4 * content->array.chunk_size / 4096) + 1);
 					}
 				}
+				if (okcnt < content->array.raid_disks
+				    && conf_get_readd()) {
+					/* If any devices did not get added
+					 * because the kernel rejected them based
+					 * on event count, try adding them again.
+					 * The bitmap might allow them to be
+					 * included - or they will become spares
+					 */
+					for (i=0; i<=bestcnt; i++) {
+						int j = best[i];
+						if (j >= 0 && !devices[j].uptodate) {
+							rv = add_disk(mdfd, st, content,
+								      &devices[j].i);
+							if (rv == 0 && verbose >= 0)
+								fprintf(stderr, Name ": %s has been re-added.\n",
+									devices[j].devname);
+						}
+					}
+				}
 				wait_for(mddev, mdfd);
 				close(mdfd);
 				if (auto_assem) {
diff --git a/Incremental.c b/Incremental.c
index 1ff0731..c109267 100644
--- a/Incremental.c
+++ b/Incremental.c
@@ -355,6 +355,18 @@ int Incremental(char *devname, int verbose, int runstop,
 		else
 			strcpy(chosen_name, devnum2devname(mp->devnum));
 
+		/* It is only OK to add drives to a running array if
+		 * the action=re-add policy is in effect
+		 */
+		if (!conf_get_readd()) {
+			if (ioctl(mdfd, GET_ARRAY_INFO, &ainf) == 0) {
+				fprintf(stderr, Name
+					": not adding %s to active array %s\n",
+					devname, chosen_name);
+				close(mdfd);
+				return 2;
+			}
+		}
 		sra = sysfs_read(mdfd, fd2devnum(mdfd), (GET_DEVS | GET_STATE));
 
 		if (sra->devs) {
@@ -470,7 +482,7 @@ int Incremental(char *devname, int verbose, int runstop,
 
 	map_unlock(&map);
 	if (runstop > 0 || active_disks >= info.array.working_disks) {
-		struct mdinfo *sra;
+		struct mdinfo *sra, *dsk;
 		/* Let's try to start it */
 		if (match && match->bitmap_file) {
 			int bmfd = open(match->bitmap_file, O_RDWR);
@@ -491,7 +503,8 @@ int Incremental(char *devname, int verbose, int runstop,
 			}
 			close(bmfd);
 		}
-		sra = sysfs_read(mdfd, fd2devnum(mdfd), 0);
+		sra = sysfs_read(mdfd, fd2devnum(mdfd),
+				 GET_DEVS|GET_OFFSET|GET_SIZE|GET_STATE);
 		if ((sra == NULL || active_disks >= info.array.working_disks)
 		    && trustworthy != FOREIGN)
 			rv = ioctl(mdfd, RUN_ARRAY, NULL);
@@ -511,6 +524,15 @@ int Incremental(char *devname, int verbose, int runstop,
 				devname, chosen_name, strerror(errno));
 			rv = 1;
 		}
+		if (conf_get_readd()) {
+			/* anything that just fell out could usefully be re-added */
+			for (dsk = sra->devs ; dsk ; dsk = dsk->next) {
+				if (add_disk(mdfd, st, sra, dsk) == 0)
+					fprintf(stderr, Name
+						": %s re-added to %s\n",
+						dsk->sys_name, chosen_name);
+			}
+		}
 	} else {
 		if (verbose >= 0)
 			fprintf(stderr, Name