The patch titled
md: improve the is_mddev_idle test fix
has been removed from the -mm tree. Its filename was
md-improve-the-is_mddev_idle-test-fix.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: md: improve the is_mddev_idle test fix
From: NeilBrown <neilb@xxxxxxx>
Don't use 'unsigned' variable to track sync vs non-sync IO, as the only thing
we want to do with them is a signed comparison, and fix up the comment which
had become quite wrong.
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/md/md.c | 35 ++++++++++++++++++++++-------------
include/linux/raid/md_k.h | 2 +-
2 files changed, 23 insertions(+), 14 deletions(-)
diff -puN drivers/md/md.c~md-improve-the-is_mddev_idle-test-fix drivers/md/md.c
--- a/drivers/md/md.c~md-improve-the-is_mddev_idle-test-fix
+++ a/drivers/md/md.c
@@ -5091,7 +5091,7 @@ static int is_mddev_idle(mddev_t *mddev)
mdk_rdev_t * rdev;
struct list_head *tmp;
int idle;
- unsigned long curr_events;
+ long curr_events;
idle = 1;
ITERATE_RDEV(mddev,rdev,tmp) {
@@ -5099,20 +5099,29 @@ static int is_mddev_idle(mddev_t *mddev)
curr_events = disk_stat_read(disk, sectors[0]) +
disk_stat_read(disk, sectors[1]) -
atomic_read(&disk->sync_io);
- /* The difference between curr_events and last_events
- * will be affected by any new non-sync IO (making
- * curr_events bigger) and any difference in the amount of
- * in-flight syncio (making current_events bigger or smaller)
- * The amount in-flight is currently limited to
- * 32*64K in raid1/10 and 256*PAGE_SIZE in raid5/6
- * which is at most 4096 sectors.
- * These numbers are fairly fragile and should be made
- * more robust, probably by enforcing the
- * 'window size' that md_do_sync sort-of uses.
+ /* sync IO will cause sync_io to increase before the disk_stats
+ * as sync_io is counted when a request starts, and
+ * disk_stats is counted when it completes.
+ * So resync activity will cause curr_events to be smaller than
+ * when there was no such activity.
+ * non-sync IO will cause disk_stat to increase without
+ * increasing sync_io so curr_events will (eventually)
+ * be larger than it was before. Once it becomes
+ * substantially larger, the test below will cause
+ * the array to appear non-idle, and resync will slow
+ * down.
+ * If there is a lot of outstanding resync activity when
+ * we set last_event to curr_events, then all that activity
+ * completing might cause the array to appear non-idle
+ * and resync will be slowed down even though there might
+ * not have been non-resync activity. This will only
+ * happen once though. 'last_events' will soon reflect
+ * the state where there is little or no outstanding
+ * resync requests, and further resync activity will
+ * always make curr_events less than last_events.
*
- * Note: the following is an unsigned comparison.
*/
- if ((long)curr_events - (long)rdev->last_events > 4096) {
+ if (curr_events - rdev->last_events > 4096) {
rdev->last_events = curr_events;
idle = 0;
}
diff -puN include/linux/raid/md_k.h~md-improve-the-is_mddev_idle-test-fix include/linux/raid/md_k.h
--- a/include/linux/raid/md_k.h~md-improve-the-is_mddev_idle-test-fix
+++ a/include/linux/raid/md_k.h
@@ -51,7 +51,7 @@ struct mdk_rdev_s
sector_t size; /* Device size (in blocks) */
mddev_t *mddev; /* RAID array if running */
- unsigned long last_events; /* IO event timestamp */
+ long last_events; /* IO event timestamp */
struct block_device *bdev; /* block device handle */
_
Patches currently in -mm which might be from neilb@xxxxxxx are
origin.patch
mm-revert-kernel_ds-buffered-write-optimisation.patch
raid5-add-the-stripe_queue-object-for-tracking-raid.patch
raid5-add-the-stripe_queue-object-for-tracking-raid-io-requests-take2.patch
raid5-use-stripe_queues-to-prioritize-the-most.patch
fs-introduce-vfs_path_lookup.patch
sunrpc-use-vfs_path_lookup.patch
nfsctl-use-vfs_path_lookup.patch
fs-mark-link_path_walk-static.patch
fs-remove-path_walk-export.patch
-
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