4 files changed, 125 insertions, 39 deletions

diff --git a/Documentation/md.txt b/Documentation/md.txt
index fc94770f44ab..993fba37b7d1 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -357,14 +357,14 @@ Each directory contains:
         written to, that device.
 
       state
-        A file recording the current state of the device in the array
+        A file recording the current state of the device in the array
         which can be a comma separated list of
               faulty   - device has been kicked from active use due to
-                         a detected fault or it has unacknowledged bad
-                         blocks
+                         a detected fault, or it has unacknowledged bad
+                         blocks
               in_sync  - device is a fully in-sync member of the array
               writemostly - device will only be subject to read
-                         requests if there are no other options.
+                         requests if there are no other options.
                          This applies only to raid1 arrays.
               blocked  - device has failed, and the failure hasn't been
                          acknowledged yet by the metadata handler.
@@ -374,6 +374,13 @@ Each directory contains:
                          This includes spares that are in the process
                          of being recovered to
               write_error - device has ever seen a write error.
+              want_replacement - device is (mostly) working but probably
+                         should be replaced, either due to errors or
+                         due to user request.
+              replacement - device is a replacement for another active
+                         device with same raid_disk.
+
+
         This list may grow in future.
         This can be written to.
         Writing "faulty"  simulates a failure on the device.
@@ -386,6 +393,13 @@ Each directory contains:
         Writing "in_sync" sets the in_sync flag.
         Writing "write_error" sets writeerrorseen flag.
         Writing "-write_error" clears writeerrorseen flag.
+        Writing "want_replacement" is allowed at any time except to a
+                replacement device or a spare.  It sets the flag.
+        Writing "-want_replacement" is allowed at any time.  It clears
+                the flag.
+        Writing "replacement" or "-replacement" is only allowed before
+                starting the array.  It sets or clears the flag.
+
 
         This file responds to select/poll. Any change to 'faulty'
         or 'blocked' causes an event.
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 0e2288824938..be569eb41a93 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1714,6 +1714,8 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *rdev)
                 }
                 if (sb->devflags & WriteMostly1)
                         set_bit(WriteMostly, &rdev->flags);
+                if (le32_to_cpu(sb->feature_map) & MD_FEATURE_REPLACEMENT)
+                        set_bit(Replacement, &rdev->flags);
         } else /* MULTIPATH are always insync */
                 set_bit(In_sync, &rdev->flags);
 
@@ -1767,6 +1769,9 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
                 sb->recovery_offset =
                         cpu_to_le64(rdev->recovery_offset);
         }
+        if (test_bit(Replacement, &rdev->flags))
+                sb->feature_map |=
+                        cpu_to_le32(MD_FEATURE_REPLACEMENT);
 
         if (mddev->reshape_position != MaxSector) {
                 sb->feature_map |= cpu_to_le32(MD_FEATURE_RESHAPE_ACTIVE);
@@ -2560,6 +2565,15 @@ state_show(struct md_rdev *rdev, char *page)
                 len += sprintf(page+len, "%swrite_error", sep);
                 sep = ",";
         }
+        if (test_bit(WantReplacement, &rdev->flags)) {
+                len += sprintf(page+len, "%swant_replacement", sep);
+                sep = ",";
+        }
+        if (test_bit(Replacement, &rdev->flags)) {
+                len += sprintf(page+len, "%sreplacement", sep);
+                sep = ",";
+        }
+
         return len+sprintf(page+len, "\n");
 }
 
@@ -2628,6 +2642,42 @@ state_store(struct md_rdev *rdev, const char *buf, size_t len)
         } else if (cmd_match(buf, "-write_error")) {
                 clear_bit(WriteErrorSeen, &rdev->flags);
                 err = 0;
+        } else if (cmd_match(buf, "want_replacement")) {
+                /* Any non-spare device that is not a replacement can
+                 * become want_replacement at any time, but we then need to
+                 * check if recovery is needed.
+                 */
+                if (rdev->raid_disk >= 0 &&
+                    !test_bit(Replacement, &rdev->flags))
+                        set_bit(WantReplacement, &rdev->flags);
+                set_bit(MD_RECOVERY_NEEDED, &rdev->mddev->recovery);
+                md_wakeup_thread(rdev->mddev->thread);
+                err = 0;
+        } else if (cmd_match(buf, "-want_replacement")) {
+                /* Clearing 'want_replacement' is always allowed.
+                 * Once replacements starts it is too late though.
+                 */
+                err = 0;
+                clear_bit(WantReplacement, &rdev->flags);
+        } else if (cmd_match(buf, "replacement")) {
+                /* Can only set a device as a replacement when array has not
+                 * yet been started.  Once running, replacement is automatic
+                 * from spares, or by assigning 'slot'.
+                 */
+                if (rdev->mddev->pers)
+                        err = -EBUSY;
+                else {
+                        set_bit(Replacement, &rdev->flags);
+                        err = 0;
+                }
+        } else if (cmd_match(buf, "-replacement")) {
+                /* Similarly, can only clear Replacement before start */
+                if (rdev->mddev->pers)
+                        err = -EBUSY;
+                else {
+                        clear_bit(Replacement, &rdev->flags);
+                        err = 0;
+                }
         }
         if (!err)
                 sysfs_notify_dirent_safe(rdev->sysfs_state);
@@ -6717,8 +6767,11 @@ static int md_seq_show(struct seq_file *seq, void *v)
                         if (test_bit(Faulty, &rdev->flags)) {
                                 seq_printf(seq, "(F)");
                                 continue;
-                        } else if (rdev->raid_disk < 0)
+                        }
+                        if (rdev->raid_disk < 0)
                                 seq_printf(seq, "(S)"); /* spare */
+                        if (test_bit(Replacement, &rdev->flags))
+                                seq_printf(seq, "(R)");
                         sectors += rdev->sectors;
                 }
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 670c10e6b484..44c63dfeeb2b 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -72,34 +72,7 @@ struct md_rdev {
          * This reduces the burden of testing multiple flags in many cases
          */
 
-        unsigned long   flags;
-#define Faulty          1               /* device is known to have a fault */
-#define In_sync         2               /* device is in_sync with rest of array */
-#define WriteMostly     4               /* Avoid reading if at all possible */
-#define AutoDetected    7               /* added by auto-detect */
-#define Blocked         8               /* An error occurred but has not yet
-                                         * been acknowledged by the metadata
-                                         * handler, so don't allow writes
-                                         * until it is cleared */
-#define WriteErrorSeen  9               /* A write error has been seen on this
-                                         * device
-                                         */
-#define FaultRecorded   10              /* Intermediate state for clearing
-                                         * Blocked.  The Fault is/will-be
-                                         * recorded in the metadata, but that
-                                         * metadata hasn't been stored safely
-                                         * on disk yet.
-                                         */
-#define BlockedBadBlocks 11             /* A writer is blocked because they
-                                         * found an unacknowledged bad-block.
-                                         * This can safely be cleared at any
-                                         * time, and the writer will re-check.
-                                         * It may be set at any time, and at
-                                         * worst the writer will timeout and
-                                         * re-check.  So setting it as
-                                         * accurately as possible is good, but
-                                         * not absolutely critical.
-                                         */
+        unsigned long   flags;  /* bit set of 'enum flag_bits' bits. */
         wait_queue_head_t blocked_wait;
 
         int desc_nr;                    /* descriptor index in the superblock */
@@ -152,6 +125,44 @@ struct md_rdev {
                 sector_t size;          /* in sectors */
         } badblocks;
 };
+enum flag_bits {
+        Faulty,                 /* device is known to have a fault */
+        In_sync,                /* device is in_sync with rest of array */
+        WriteMostly,            /* Avoid reading if at all possible */
+        AutoDetected,           /* added by auto-detect */
+        Blocked,                /* An error occurred but has not yet
+                                 * been acknowledged by the metadata
+                                 * handler, so don't allow writes
+                                 * until it is cleared */
+        WriteErrorSeen,         /* A write error has been seen on this
+                                 * device
+                                 */
+        FaultRecorded,          /* Intermediate state for clearing
+                                 * Blocked.  The Fault is/will-be
+                                 * recorded in the metadata, but that
+                                 * metadata hasn't been stored safely
+                                 * on disk yet.
+                                 */
+        BlockedBadBlocks,       /* A writer is blocked because they
+                                 * found an unacknowledged bad-block.
+                                 * This can safely be cleared at any
+                                 * time, and the writer will re-check.
+                                 * It may be set at any time, and at
+                                 * worst the writer will timeout and
+                                 * re-check.  So setting it as
+                                 * accurately as possible is good, but
+                                 * not absolutely critical.
+                                 */
+        WantReplacement,        /* This device is a candidate to be
+                                 * hot-replaced, either because it has
+                                 * reported some faults, or because
+                                 * of explicit request.
+                                 */
+        Replacement,            /* This device is a replacement for
+                                 * a want_replacement device with same
+                                 * raid_disk number.
+                                 */
+};
 
 #define BB_LEN_MASK     (0x00000000000001FFULL)
 #define BB_OFFSET_MASK  (0x7FFFFFFFFFFFFE00ULL)
@@ -482,15 +493,20 @@ static inline char * mdname (struct mddev * mddev)
 static inline int sysfs_link_rdev(struct mddev *mddev, struct md_rdev *rdev)
 {
         char nm[20];
-        sprintf(nm, "rd%d", rdev->raid_disk);
-        return sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
+        if (!test_bit(Replacement, &rdev->flags)) {
+                sprintf(nm, "rd%d", rdev->raid_disk);
+                return sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
+        } else
+                return 0;
 }
 
 static inline void sysfs_unlink_rdev(struct mddev *mddev, struct md_rdev *rdev)
 {
         char nm[20];
-        sprintf(nm, "rd%d", rdev->raid_disk);
-        sysfs_remove_link(&mddev->kobj, nm);
+        if (!test_bit(Replacement, &rdev->flags)) {
+                sprintf(nm, "rd%d", rdev->raid_disk);
+                sysfs_remove_link(&mddev->kobj, nm);
+        }
 }
 
 /*
diff --git a/include/linux/raid/md_p.h b/include/linux/raid/md_p.h
index 9e65d9e20662..6f6df86f1ae5 100644
--- a/include/linux/raid/md_p.h
+++ b/include/linux/raid/md_p.h
@@ -277,7 +277,10 @@ struct mdp_superblock_1 {
                                            */
 #define MD_FEATURE_RESHAPE_ACTIVE       4
 #define MD_FEATURE_BAD_BLOCKS           8 /* badblock list is not empty */
-
-#define MD_FEATURE_ALL                  (1|2|4|8)
+#define MD_FEATURE_REPLACEMENT          16 /* This device is replacing an
+                                            * active device with same 'role'.
+                                            * 'recovery_offset' is also set.
+                                            */
+#define MD_FEATURE_ALL                  (1|2|4|8|16)
 
 #endif