From: Anand Jain <Anand.Jain@xxxxxxxxxx>
Further to the commit
bc178622d40d87e75abc131007342429c9b03351
btrfs: use rcu_barrier() to wait for bdev puts at unmount
This patch implements a method to time wait on the __free_device()
which actually does the bdev put. This is needed as the user space
running 'btrfs fi show -d' immediately after the replace and
unmount, is still reading older information from the device.
mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg54188.html
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
[updates: bc178622d40d87e75abc131007342429c9b03351]
---
v2: Also to make sure bdev_closing is set it needs rcu_barrier(),
restored rcu_barrier().
fs/btrfs/volumes.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
fs/btrfs/volumes.h | 1 +
2 files changed, 44 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 604daf315669..ef61c34cafbf 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -27,6 +27,7 @@
#include <linux/raid/pq.h>
#include <linux/semaphore.h>
#include <linux/uuid.h>
+#include <linux/delay.h>
#include <asm/div64.h>
#include "ctree.h"
#include "extent_map.h"
@@ -254,6 +255,17 @@ static struct btrfs_device *__alloc_device(void)
return dev;
}
+static int is_device_closing(struct list_head *head)
+{
+ struct btrfs_device *dev;
+
+ list_for_each_entry(dev, head, dev_list) {
+ if (dev->bdev_closing)
+ return 1;
+ }
+ return 0;
+}
+
static noinline struct btrfs_device *__find_device(struct list_head *head,
u64 devid, u8 *uuid)
{
@@ -832,12 +844,22 @@ again:
static void __free_device(struct work_struct *work)
{
struct btrfs_device *device;
+ struct btrfs_device *new_device_addr;
device = container_of(work, struct btrfs_device, rcu_work);
if (device->bdev)
blkdev_put(device->bdev, device->mode);
+ /*
+ * If we are coming here from btrfs_close_one_device()
+ * then it allocates a new device structure for the same
+ * devid, so find device again with the devid
+ */
+ new_device_addr = __find_device(&device->fs_devices->devices,
+ device->devid, NULL);
+
+ new_device_addr->bdev_closing = 0;
rcu_string_free(device->name);
kfree(device);
}
@@ -884,6 +906,12 @@ static void btrfs_close_one_device(struct btrfs_device *device)
list_replace_rcu(&device->dev_list, &new_device->dev_list);
new_device->fs_devices = device->fs_devices;
+ /*
+ * So to wait for kworkers to finish all blkdev_puts,
+ * so device is really free when umount is done.
+ */
+ new_device->bdev_closing = 1;
+
call_rcu(&device->rcu, free_device);
}
@@ -912,6 +940,7 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
struct btrfs_fs_devices *seed_devices = NULL;
int ret;
+ int retry_cnt = 5;
mutex_lock(&uuid_mutex);
ret = __btrfs_close_devices(fs_devices);
@@ -929,10 +958,22 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
}
/*
* Wait for rcu kworkers under __btrfs_close_devices
- * to finish all blkdev_puts so device is really
- * free when umount is done.
+ * to finish all free_device()
*/
rcu_barrier();
+
+ /*
+ * Wait for a grace period so that __free_device()
+ * will actaully do the device close.
+ */
+ while (is_device_closing(&fs_devices->devices) &&
+ --retry_cnt) {
+ mdelay(1000); //1 sec
+ }
+
+ if (!(retry_cnt > 0))
+ printk(KERN_WARNING "BTRFS: %pU bdev_put didn't complete, giving up\n",
+ fs_devices->fsid);
return ret;
}
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 0ac90f8d85bd..945e49f5e17d 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -150,6 +150,7 @@ struct btrfs_device {
/* Counter to record the change of device stats */
atomic_t dev_stats_ccnt;
atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
+ int bdev_closing;
};
/*
--
2.7.0
--
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