The patch titled
md: change lifetime rules for 'md' devices
has been removed from the -mm tree. Its filename was
md-change-lifetime-rules-for-md-devices.patch
This patch was dropped because it had testing failures
------------------------------------------------------
Subject: md: change lifetime rules for 'md' devices
From: NeilBrown <neilb@xxxxxxx>
Currently md devices are created when first opened and remain in existence
until the module is unloaded. This isn't a major problem, but it somewhat
ugly.
This patch changes the lifetime rules so that an md device will disappear on
the last close if it has no state.
Locking rules depend on bd_mutex being held in do_open and __blkdev_put, and
on setting bd_disk->private_data to 'mddev'.
There is room for a race because md_probe is called early in do_open
(get_gendisk) to create the mddev. As this isn't protected by bd_mutex, a
concurrent call to md_close can destroy that mddev before do_open calls
md_open to get a reference on it. md_open and md_close are serialised by
md_mutex so the worst that can happen is that md_open finds that the mddev
structure doesn't exist after all. In this case bd_disk->private_data will be
NULL, and md_open chooses to exit with -EBUSY in this case, which is arguable
and appropriate result.
The new 'dead' field in mddev is used to track whether it is time to destroy
the mddev (if a last-close happens). It is cleared when any state is create
(set_array_info) and set when the array is stopped (do_md_stop).
mddev_put becomes simpler. It just destroys the mddev when the refcount hits
zero. This will normally be the reference held in bd_disk->private_data.
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/md/md.c | 35 +++++++++++++++++++++++++----------
include/linux/raid/md_k.h | 3 +++
2 files changed, 28 insertions(+), 10 deletions(-)
diff -puN drivers/md/md.c~md-change-lifetime-rules-for-md-devices drivers/md/md.c
--- a/drivers/md/md.c~md-change-lifetime-rules-for-md-devices
+++ a/drivers/md/md.c
@@ -226,13 +226,14 @@ static void mddev_put(mddev_t *mddev)
{
if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
return;
- if (!mddev->raid_disks && list_empty(&mddev->disks)) {
- list_del(&mddev->all_mddevs);
- spin_unlock(&all_mddevs_lock);
- blk_cleanup_queue(mddev->queue);
- kobject_unregister(&mddev->kobj);
- } else
- spin_unlock(&all_mddevs_lock);
+ list_del(&mddev->all_mddevs);
+ spin_unlock(&all_mddevs_lock);
+
+ del_gendisk(mddev->gendisk);
+ mddev->gendisk = NULL;
+ blk_cleanup_queue(mddev->queue);
+ mddev->queue = NULL;
+ kobject_unregister(&mddev->kobj);
}
static mddev_t * mddev_find(dev_t unit)
@@ -273,6 +274,7 @@ static mddev_t * mddev_find(dev_t unit)
atomic_set(&new->active, 1);
spin_lock_init(&new->write_lock);
init_waitqueue_head(&new->sb_wait);
+ new->dead = 1;
new->queue = blk_alloc_queue(GFP_KERNEL);
if (!new->queue) {
@@ -3360,6 +3362,8 @@ static int do_md_stop(mddev_t * mddev, i
mddev->array_size = 0;
mddev->size = 0;
mddev->raid_disks = 0;
+ mddev->dead = 1;
+
mddev->recovery_cp = 0;
} else if (mddev->pers)
@@ -4290,7 +4294,8 @@ static int md_ioctl(struct inode *inode,
printk(KERN_WARNING "md: couldn't set"
" array info. %d\n", err);
goto abort_unlock;
- }
+ } else
+ mddev->dead = 0;
}
goto done_unlock;
@@ -4374,6 +4379,8 @@ static int md_ioctl(struct inode *inode,
err = -EFAULT;
else
err = add_new_disk(mddev, &info);
+ if (!err)
+ mddev->dead = 0;
goto done_unlock;
}
@@ -4420,8 +4427,12 @@ static int md_open(struct inode *inode,
* Succeed if we can lock the mddev, which confirms that
* it isn't being stopped right now.
*/
- mddev_t *mddev = inode->i_bdev->bd_disk->private_data;
- int err;
+ mddev_t *mddev;
+ int err = -EBUSY;
+
+ mddev = inode->i_bdev->bd_disk->private_data;
+ if (!mddev)
+ goto out;
if ((err = mutex_lock_interruptible_nested(&mddev->reconfig_mutex, 1)))
goto out;
@@ -4440,6 +4451,10 @@ static int md_release(struct inode *inod
mddev_t *mddev = inode->i_bdev->bd_disk->private_data;
BUG_ON(!mddev);
+ if (inode->i_bdev->bd_openers == 0 && mddev->dead) {
+ inode->i_bdev->bd_disk->private_data = NULL;
+ mddev_put(mddev);
+ }
mddev_put(mddev);
return 0;
diff -puN include/linux/raid/md_k.h~md-change-lifetime-rules-for-md-devices include/linux/raid/md_k.h
--- a/include/linux/raid/md_k.h~md-change-lifetime-rules-for-md-devices
+++ a/include/linux/raid/md_k.h
@@ -119,6 +119,9 @@ struct mddev_s
#define MD_CHANGE_PENDING 2 /* superblock update in progress */
int ro;
+ int dead; /* array should be discarded on
+ * last close
+ */
struct gendisk *gendisk;
_
Patches currently in -mm which might be from neilb@xxxxxxx are
origin.patch
auth_gss-unregister-gss_domain-when-unloading-module-fix.patch
fix-sunrpc-wakeup-execute-race-condition.patch
lockdep-annotate-nfs-nfsd-in-kernel-sockets.patch
lockdep-annotate-nfs-nfsd-in-kernel-sockets-tidy.patch
remove-lock_key-approach-to-managing-nested-bd_mutex-locks.patch
simplify-some-aspects-of-bd_mutex-nesting.patch
use-mutex_lock_nested-for-bd_mutex-to-avoid-lockdep-warning.patch
avoid-lockdep-warning-in-md.patch
bdev-fix-bd_part_count-leak.patch
lockdep-annotate-nfsd4-recover-code.patch
md-tidy-up-device-change-notification-when-an-md-array-is-stopped.patch
md-define-raid5_mergeable_bvec.patch
md-handle-bypassing-the-read-cache-assuming-nothing-fails.patch
md-allow-reads-that-have-bypassed-the-cache-to-be-retried-on-failure.patch
md-allow-reads-that-have-bypassed-the-cache-to-be-retried-on-failure-fix.patch
md-enable-bypassing-cache-for-reads.patch
md-conditionalize-some-code.patch
md-dm-reduce-stack-usage-with-stacked-block-devices.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
