Vova,
Let's keep flies and cutlets separately. It seems we can easily satisfy
push-backup needs by implementing freeze/thaw ploop ioctls without
tackling generic code at all, see a patch in attachment (unless I missed
something obvious). And apart from these ploop/push-backup stuff, if you
think your changes for freeze_bdev() and thaw_bdev() are useful, send
them upstream, so we'll back-port them later, when they are accepted
upstream (unless I missed some scenario for which those changes matter
for us). In the other words, I think we have to keep our vz7 generic
code base closer to ms, unless we have good reason to deviate.
Thanks,
Maxim
On 07/12/2016 03:04 AM, Vladimir Davydov wrote:
It's possible to freeze a bdev which is not mounted. In this case
freeze_bdev() only increments bd_fsfrozen_count in order to prevent the
bdev from being mounted and does nothing else. A second freeze attempt
on the same device is supposed to increment bd_fsfrozen_count again, but
it results in NULL ptr dereference, because freeze_bdev() doesn't check
the return value of get_super(). Fix that.
Signed-off-by: Vladimir Davydov <vdavy...@virtuozzo.com>
---
fs/block_dev.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 4575c62d8b0b..325ee7161fbf 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -227,7 +227,8 @@ struct super_block *freeze_bdev(struct block_device *bdev)
* thaw_bdev drops it.
*/
sb = get_super(bdev);
- drop_super(sb);
+ if (sb)
+ drop_super(sb);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return sb;
}
The ioctls simply freeze and thaw ploop bdev.
Caveats:
1) If no fs mounted, the ioctls have no effect.
2) No nested freeze: many PLOOP_IOC_FREEZE ioctls have the same effect as one.
3) The same for thaw.
Signed-off-by: Maxim Patlasov <mpatla...@virtuozzo.com>
---
drivers/block/ploop/dev.c | 38 ++++++++++++++++++++++++++++++++++++++
include/linux/ploop/ploop.h | 1 +
include/linux/ploop/ploop_if.h | 6 ++++++
3 files changed, 45 insertions(+)
diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
index 6d449b7..e583d10 100644
--- a/drivers/block/ploop/dev.c
+++ b/drivers/block/ploop/dev.c
@@ -4892,6 +4892,38 @@ static int ploop_push_backup_stop(struct ploop_device *plo, unsigned long arg)
return copy_to_user((void*)arg, &ctl, sizeof(ctl));
}
+static int ploop_freeze(struct ploop_device *plo, struct block_device *bdev)
+{
+ struct super_block *sb = plo->sb;
+
+ if (sb)
+ return 0;
+
+ sb = freeze_bdev(bdev);
+ if (sb && IS_ERR(sb))
+ return PTR_ERR(sb);
+ if (!sb)
+ thaw_bdev(bdev, sb);
+
+ plo->sb = sb;
+ return 0;
+}
+
+static int ploop_thaw(struct ploop_device *plo, struct block_device *bdev)
+{
+ struct super_block *sb = plo->sb;
+ int err;
+
+ if (!sb)
+ return 0;
+
+ err = thaw_bdev(bdev, sb);
+ if (!err)
+ plo->sb = NULL;
+
+ return err;
+}
+
static int ploop_ioctl(struct block_device *bdev, fmode_t fmode, unsigned int cmd,
unsigned long arg)
{
@@ -5005,6 +5037,12 @@ static int ploop_ioctl(struct block_device *bdev, fmode_t fmode, unsigned int cm
case PLOOP_IOC_PUSH_BACKUP_STOP:
err = ploop_push_backup_stop(plo, arg);
break;
+ case PLOOP_IOC_FREEZE:
+ err = ploop_freeze(plo, bdev);
+ break;
+ case PLOOP_IOC_THAW:
+ err = ploop_thaw(plo, bdev);
+ break;
default:
err = -EINVAL;
}
diff --git a/include/linux/ploop/ploop.h b/include/linux/ploop/ploop.h
index 859fe51..e60ada4 100644
--- a/include/linux/ploop/ploop.h
+++ b/include/linux/ploop/ploop.h
@@ -414,6 +414,7 @@ struct ploop_device
struct block_device *bdev;
struct request_queue *queue;
struct task_struct *thread;
+ struct super_block *sb;
struct rb_node link;
/* someone who wants to quiesce state-machine waits
diff --git a/include/linux/ploop/ploop_if.h b/include/linux/ploop/ploop_if.h
index a098ca9..302ace9 100644
--- a/include/linux/ploop/ploop_if.h
+++ b/include/linux/ploop/ploop_if.h
@@ -352,6 +352,12 @@ struct ploop_track_extent
/* Stop push backup */
#define PLOOP_IOC_PUSH_BACKUP_STOP _IOR(PLOOPCTLTYPE, 31, struct ploop_push_backup_stop_ctl)
+/* Freeze FS mounted over ploop */
+#define PLOOP_IOC_FREEZE _IO(PLOOPCTLTYPE, 32)
+
+/* Unfreeze FS mounted over ploop */
+#define PLOOP_IOC_THAW _IO(PLOOPCTLTYPE, 33)
+
/* Events exposed via /sys/block/ploopN/pstate/event */
#define PLOOP_EVENT_ABORTED 1
#define PLOOP_EVENT_STOPPED 2
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