[PATCH 005 of 9] md: Replace magic numbers in sb_dirty with well defined bit flags

From: NeilBrown
Date: Mon Jul 31 2006 - 03:32:40 EST


Instead of magic numbers (0,1,2,3) in sb_dirty, we have
some flags instead:
MD_CHANGE_DEVS
Some device state has changed requiring superblock update
on all devices.
MD_CHANGE_CLEAN
The array has transitions from 'clean' to 'dirty' or back,
requiring a superblock update on active devices, but possibly
not on spares
MD_CHANGE_PENDING
A superblock update is underway.

We wait for an update to complete by waiting for all flags to
be clear. A flag can be set at any time, even during an update,
without risk that the change will be lost.

Stop exporting md_update_sb - isn't needed.


Signed-off-by: Neil Brown <neilb@xxxxxxx>

### Diffstat output
./drivers/md/md.c | 68 +++++++++++++++++++++++---------------------
./drivers/md/multipath.c | 3 -
./drivers/md/raid1.c | 2 -
./drivers/md/raid10.c | 2 -
./drivers/md/raid5.c | 8 ++---
./include/linux/raid/md.h | 1
./include/linux/raid/md_k.h | 6 +++
7 files changed, 49 insertions(+), 41 deletions(-)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c 2006-07-31 17:23:57.000000000 +1000
+++ ./drivers/md/md.c 2006-07-31 17:24:34.000000000 +1000
@@ -1587,7 +1587,7 @@ static void sync_sbs(mddev_t * mddev, in
}
}

-void md_update_sb(mddev_t * mddev)
+static void md_update_sb(mddev_t * mddev, int force_change)
{
int err;
struct list_head *tmp;
@@ -1597,18 +1597,25 @@ void md_update_sb(mddev_t * mddev)

repeat:
spin_lock_irq(&mddev->write_lock);
- sync_req = mddev->in_sync;
- mddev->utime = get_seconds();
- if (mddev->sb_dirty == 3)
+
+ set_bit(MD_CHANGE_PENDING, &mddev->flags);
+ if (test_and_clear_bit(MD_CHANGE_DEVS, &mddev->flags))
+ force_change = 1;
+ if (test_and_clear_bit(MD_CHANGE_CLEAN, &mddev->flags))
/* just a clean<-> dirty transition, possibly leave spares alone,
* though if events isn't the right even/odd, we will have to do
* spares after all
*/
nospares = 1;
+ if (force_change)
+ nospares = 0;
+
+ sync_req = mddev->in_sync;
+ mddev->utime = get_seconds();

/* If this is just a dirty<->clean transition, and the array is clean
* and 'events' is odd, we can roll back to the previous clean state */
- if (mddev->sb_dirty == 3
+ if (nospares
&& (mddev->in_sync && mddev->recovery_cp == MaxSector)
&& (mddev->events & 1))
mddev->events--;
@@ -1639,7 +1646,6 @@ repeat:
MD_BUG();
mddev->events --;
}
- mddev->sb_dirty = 2;
sync_sbs(mddev, nospares);

/*
@@ -1647,7 +1653,7 @@ repeat:
* nonpersistent superblocks
*/
if (!mddev->persistent) {
- mddev->sb_dirty = 0;
+ clear_bit(MD_CHANGE_PENDING, &mddev->flags);
spin_unlock_irq(&mddev->write_lock);
wake_up(&mddev->sb_wait);
return;
@@ -1684,20 +1690,20 @@ repeat:
break;
}
md_super_wait(mddev);
- /* if there was a failure, sb_dirty was set to 1, and we re-write super */
+ /* if there was a failure, MD_CHANGE_DEVS was set, and we re-write super */

spin_lock_irq(&mddev->write_lock);
- if (mddev->in_sync != sync_req|| mddev->sb_dirty == 1) {
+ if (mddev->in_sync != sync_req ||
+ test_bit(MD_CHANGE_DEVS, &mddev->flags)) {
/* have to write it out again */
spin_unlock_irq(&mddev->write_lock);
goto repeat;
}
- mddev->sb_dirty = 0;
+ clear_bit(MD_CHANGE_PENDING, &mddev->flags);
spin_unlock_irq(&mddev->write_lock);
wake_up(&mddev->sb_wait);

}
-EXPORT_SYMBOL_GPL(md_update_sb);

/* words written to sysfs files may, or my not, be \n terminated.
* We want to accept with case. For this we use cmd_match.
@@ -1770,7 +1776,7 @@ state_store(mdk_rdev_t *rdev, const char
else {
mddev_t *mddev = rdev->mddev;
kick_rdev_from_array(rdev);
- md_update_sb(mddev);
+ md_update_sb(mddev, 1);
md_new_event(mddev);
err = 0;
}
@@ -2413,7 +2419,7 @@ array_state_store(mddev_t *mddev, const
spin_lock_irq(&mddev->write_lock);
if (atomic_read(&mddev->writes_pending) == 0) {
mddev->in_sync = 1;
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_CLEAN, &mddev->flags);
}
spin_unlock_irq(&mddev->write_lock);
} else {
@@ -2425,7 +2431,7 @@ array_state_store(mddev_t *mddev, const
case active:
if (mddev->pers) {
restart_array(mddev);
- mddev->sb_dirty = 0;
+ clear_bit(MD_CHANGE_CLEAN, &mddev->flags);
wake_up(&mddev->sb_wait);
err = 0;
} else {
@@ -2530,7 +2536,7 @@ size_store(mddev_t *mddev, const char *b

if (mddev->pers) {
err = update_size(mddev, size);
- md_update_sb(mddev);
+ md_update_sb(mddev, 1);
} else {
if (mddev->size == 0 ||
mddev->size > size)
@@ -3098,8 +3104,8 @@ static int do_md_run(mddev_t * mddev)

set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

- if (mddev->sb_dirty)
- md_update_sb(mddev);
+ if (mddev->flags)
+ md_update_sb(mddev, 0);

set_capacity(disk, mddev->array_size<<1);

@@ -3262,10 +3268,10 @@ static int do_md_stop(mddev_t * mddev, i
if (mddev->ro)
mddev->ro = 0;
}
- if (!mddev->in_sync || mddev->sb_dirty) {
+ if (!mddev->in_sync || mddev->flags) {
/* mark array as shutdown cleanly */
mddev->in_sync = 1;
- md_update_sb(mddev);
+ md_update_sb(mddev, 1);
}
if (mode == 1)
set_disk_ro(disk, 1);
@@ -3734,7 +3740,7 @@ static int hot_remove_disk(mddev_t * mdd
goto busy;

kick_rdev_from_array(rdev);
- md_update_sb(mddev);
+ md_update_sb(mddev, 1);
md_new_event(mddev);

return 0;
@@ -3811,7 +3817,7 @@ static int hot_add_disk(mddev_t * mddev,

rdev->raid_disk = -1;

- md_update_sb(mddev);
+ md_update_sb(mddev, 1);

/*
* Kick recovery, maybe this spare has to be added to the
@@ -3942,7 +3948,8 @@ static int set_array_info(mddev_t * mdde

mddev->max_disks = MD_SB_DISKS;

- mddev->sb_dirty = 1;
+ mddev->flags = 0;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);

mddev->default_bitmap_offset = MD_SB_BYTES >> 9;
mddev->bitmap_offset = 0;
@@ -4111,7 +4118,7 @@ static int update_array_info(mddev_t *md
mddev->bitmap_offset = 0;
}
}
- md_update_sb(mddev);
+ md_update_sb(mddev, 1);
return rv;
}

@@ -4947,12 +4954,12 @@ void md_write_start(mddev_t *mddev, stru
spin_lock_irq(&mddev->write_lock);
if (mddev->in_sync) {
mddev->in_sync = 0;
- mddev->sb_dirty = 3;
+ set_bit(MD_CHANGE_CLEAN, &mddev->flags);
md_wakeup_thread(mddev->thread);
}
spin_unlock_irq(&mddev->write_lock);
}
- wait_event(mddev->sb_wait, mddev->sb_dirty==0);
+ wait_event(mddev->sb_wait, mddev->flags==0);
}

void md_write_end(mddev_t *mddev)
@@ -5222,7 +5229,6 @@ void md_do_sync(mddev_t *mddev)
!test_bit(In_sync, &rdev->flags) &&
rdev->recovery_offset < mddev->curr_resync)
rdev->recovery_offset = mddev->curr_resync;
- mddev->sb_dirty = 1;
}
}

@@ -5279,7 +5285,7 @@ void md_check_recovery(mddev_t *mddev)
}

if ( ! (
- mddev->sb_dirty ||
+ mddev->flags ||
test_bit(MD_RECOVERY_NEEDED, &mddev->recovery) ||
test_bit(MD_RECOVERY_DONE, &mddev->recovery) ||
(mddev->safemode == 1) ||
@@ -5295,14 +5301,14 @@ void md_check_recovery(mddev_t *mddev)
if (mddev->safemode && !atomic_read(&mddev->writes_pending) &&
!mddev->in_sync && mddev->recovery_cp == MaxSector) {
mddev->in_sync = 1;
- mddev->sb_dirty = 3;
+ set_bit(MD_CHANGE_CLEAN, &mddev->flags);
}
if (mddev->safemode == 1)
mddev->safemode = 0;
spin_unlock_irq(&mddev->write_lock);

- if (mddev->sb_dirty)
- md_update_sb(mddev);
+ if (mddev->flags)
+ md_update_sb(mddev, 0);


if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) &&
@@ -5321,7 +5327,7 @@ void md_check_recovery(mddev_t *mddev)
/* activate any spares */
mddev->pers->spare_active(mddev);
}
- md_update_sb(mddev);
+ md_update_sb(mddev, 1);

/* if array is no-longer degraded, then any saved_raid_disk
* information must be scrapped

diff .prev/drivers/md/multipath.c ./drivers/md/multipath.c
--- .prev/drivers/md/multipath.c 2006-07-31 17:23:57.000000000 +1000
+++ ./drivers/md/multipath.c 2006-07-31 17:24:34.000000000 +1000
@@ -253,7 +253,7 @@ static void multipath_error (mddev_t *md
char b[BDEVNAME_SIZE];
clear_bit(In_sync, &rdev->flags);
set_bit(Faulty, &rdev->flags);
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);
conf->working_disks--;
printk(KERN_ALERT "multipath: IO failure on %s,"
" disabling IO path. \n Operation continuing"
@@ -470,7 +470,6 @@ static int multipath_run (mddev_t *mddev
}

conf->raid_disks = mddev->raid_disks;
- mddev->sb_dirty = 1;
conf->mddev = mddev;
spin_lock_init(&conf->device_lock);
INIT_LIST_HEAD(&conf->retry_list);

diff .prev/drivers/md/raid1.c ./drivers/md/raid1.c
--- .prev/drivers/md/raid1.c 2006-07-31 17:24:24.000000000 +1000
+++ ./drivers/md/raid1.c 2006-07-31 17:24:34.000000000 +1000
@@ -966,7 +966,7 @@ static void error(mddev_t *mddev, mdk_rd
}
clear_bit(In_sync, &rdev->flags);
set_bit(Faulty, &rdev->flags);
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);
printk(KERN_ALERT "raid1: Disk failure on %s, disabling device. \n"
" Operation continuing on %d devices\n",
bdevname(rdev->bdev,b), conf->working_disks);

diff .prev/drivers/md/raid10.c ./drivers/md/raid10.c
--- .prev/drivers/md/raid10.c 2006-07-31 17:24:34.000000000 +1000
+++ ./drivers/md/raid10.c 2006-07-31 17:24:34.000000000 +1000
@@ -960,7 +960,7 @@ static void error(mddev_t *mddev, mdk_rd
}
clear_bit(In_sync, &rdev->flags);
set_bit(Faulty, &rdev->flags);
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);
printk(KERN_ALERT "raid10: Disk failure on %s, disabling device. \n"
" Operation continuing on %d devices\n",
bdevname(rdev->bdev,b), conf->working_disks);

diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c 2006-07-31 17:23:57.000000000 +1000
+++ ./drivers/md/raid5.c 2006-07-31 17:24:34.000000000 +1000
@@ -696,7 +696,7 @@ static void error(mddev_t *mddev, mdk_rd
PRINTK("raid5: error called\n");

if (!test_bit(Faulty, &rdev->flags)) {
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);
if (test_bit(In_sync, &rdev->flags)) {
conf->working_disks--;
mddev->degraded++;
@@ -2781,9 +2781,9 @@ static sector_t reshape_request(mddev_t
wait_event(conf->wait_for_overlap,
atomic_read(&conf->reshape_stripes)==0);
mddev->reshape_position = conf->expand_progress;
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);
md_wakeup_thread(mddev->thread);
- wait_event(mddev->sb_wait, mddev->sb_dirty == 0 ||
+ wait_event(mddev->sb_wait, mddev->flags == 0 ||
kthread_should_stop());
spin_lock_irq(&conf->device_lock);
conf->expand_lo = mddev->reshape_position;
@@ -3605,7 +3605,7 @@ static int raid5_start_reshape(mddev_t *
mddev->degraded = (conf->raid_disks - conf->previous_raid_disks) - added_devices;
mddev->raid_disks = conf->raid_disks;
mddev->reshape_position = 0;
- mddev->sb_dirty = 1;
+ set_bit(MD_CHANGE_DEVS, &mddev->flags);

clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);

diff .prev/include/linux/raid/md.h ./include/linux/raid/md.h
--- .prev/include/linux/raid/md.h 2006-07-31 17:23:57.000000000 +1000
+++ ./include/linux/raid/md.h 2006-07-31 17:24:34.000000000 +1000
@@ -93,7 +93,6 @@ extern int sync_page_io(struct block_dev
extern void md_do_sync(mddev_t *mddev);
extern void md_new_event(mddev_t *mddev);

-extern void md_update_sb(mddev_t * mddev);

#endif


diff .prev/include/linux/raid/md_k.h ./include/linux/raid/md_k.h
--- .prev/include/linux/raid/md_k.h 2006-07-31 17:23:57.000000000 +1000
+++ ./include/linux/raid/md_k.h 2006-07-31 17:24:34.000000000 +1000
@@ -114,7 +114,11 @@ struct mddev_s
dev_t unit;
int md_minor;
struct list_head disks;
- int sb_dirty;
+ unsigned long flags;
+#define MD_CHANGE_DEVS 0 /* Some device status has changed */
+#define MD_CHANGE_CLEAN 1 /* transition to or from 'clean' */
+#define MD_CHANGE_PENDING 2 /* superblock update in progress */
+
int ro;

struct gendisk *gendisk;
-
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