md: create externally visible flags for supporting hot-replace.
hot-replace is a feature being added to md which will allow a
device to be replaced without removing it from the array first.
With hot-replace a spare can be activated and recovery can start while
the original device is still in place, thus allowing a transition from
an unreliable device to a reliable device without leaving the array
degraded during the transition. It can also be use when the original
device is still reliable but it not wanted for some reason.
This will eventually be supported in RAID4/5/6 and RAID10.
This patch adds a super-block flag to distinguish the replacement
device. If an old kernel sees this flag it will reject the device.
It also adds two per-device flags which are viewable and settable via
sysfs.
"want_replacement" can be set to request that a device be replaced.
"replacement" is set to show that this device is replacing another
device.
The "rd%d" links in /sys/block/mdXx/md only apply to the original
device, not the replacement. We currently don't make links for the
replacement - there doesn't seem to be a need.
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/Documentation/md.txt b/Documentation/md.txt
index fc94770..993fba3 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -357,14 +357,14 @@
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 @@
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 @@
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 0e22888..be569eb 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1714,6 +1714,8 @@
}
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 @@
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 @@
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 @@
} 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 @@
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 670c10e6..44c63df 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -72,34 +72,7 @@
* 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 @@
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 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 9e65d9e..6f6df86 100644
--- a/include/linux/raid/md_p.h
+++ b/include/linux/raid/md_p.h
@@ -277,7 +277,10 @@
*/
#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