md: rearrange recovery_flags

Currently there are lots of flags with the same confusing prefix
"MD_REOCVERY_", and there are two main types of flags, sync thread runnng
status, I prefer prefix "SYNC_THREAD_", and sync thread action, I perfer
prefix "SYNC_ACTION_".

For now, rearrange and update comment to improve code readability,
there are no functional changes.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240611132251.1967786-2-yukuai1@huaweicloud.com

drivers/md/md.h

@@ -551,22 +551,46 @@ struct mddev {
 };
 
 enum recovery_flags {
+	/* flags for sync thread running status */
+
+	/*
+	 * set when one of sync action is set and new sync thread need to be
+	 * registered, or just add/remove spares from conf.
+	 */
+	MD_RECOVERY_NEEDED,
+	/* sync thread is running, or about to be started */
+	MD_RECOVERY_RUNNING,
+	/* sync thread needs to be aborted for some reason */
+	MD_RECOVERY_INTR,
+	/* sync thread is done and is waiting to be unregistered */
+	MD_RECOVERY_DONE,
+	/* running sync thread must abort immediately, and not restart */
+	MD_RECOVERY_FROZEN,
+	/* waiting for pers->start() to finish */
+	MD_RECOVERY_WAIT,
+	/* interrupted because io-error */
+	MD_RECOVERY_ERROR,
+
+	/* flags determines sync action */
+
+	/* if just this flag is set, action is resync. */
+	MD_RECOVERY_SYNC,
+	/*
+	 * paired with MD_RECOVERY_SYNC, if MD_RECOVERY_CHECK is not set,
+	 * action is repair, means user requested resync.
+	 */
+	MD_RECOVERY_REQUESTED,
 	/*
-	 * If neither SYNC or RESHAPE are set, then it is a recovery.
+	 * paired with MD_RECOVERY_SYNC and MD_RECOVERY_REQUESTED, action is
+	 * check.
 	 */
-	MD_RECOVERY_RUNNING,	/* a thread is running, or about to be started */
-	MD_RECOVERY_SYNC,	/* actually doing a resync, not a recovery */
-	MD_RECOVERY_RECOVER,	/* doing recovery, or need to try it. */
-	MD_RECOVERY_INTR,	/* resync needs to be aborted for some reason */
-	MD_RECOVERY_DONE,	/* thread is done and is waiting to be reaped */
-	MD_RECOVERY_NEEDED,	/* we might need to start a resync/recover */
-	MD_RECOVERY_REQUESTED,	/* user-space has requested a sync (used with SYNC) */
-	MD_RECOVERY_CHECK,	/* user-space request for check-only, no repair */
-	MD_RECOVERY_RESHAPE,	/* A reshape is happening */
-	MD_RECOVERY_FROZEN,	/* User request to abort, and not restart, any action */
-	MD_RECOVERY_ERROR,	/* sync-action interrupted because io-error */
-	MD_RECOVERY_WAIT,	/* waiting for pers->start() to finish */
-	MD_RESYNCING_REMOTE,	/* remote node is running resync thread */
+	MD_RECOVERY_CHECK,
+	/* recovery, or need to try it */
+	MD_RECOVERY_RECOVER,
+	/* reshape */
+	MD_RECOVERY_RESHAPE,
+	/* remote node is running resync thread */
+	MD_RESYNCING_REMOTE,
 };
 
 enum md_ro_state {