From: Anand Jain <anand.jain@xxxxxxxxxx>
When FS in unmounted we need to check generation number as well
since devid+uuid combination could match with the missing replaced
disk when it reappears, and without this patch it might pair with
the replaced disk again.
device_list_add() function is called in the following threads,
mount device option
mount argument
ioctl BTRFS_IOC_SCAN_DEV (btrfs dev scan)
ioctl BTRFS_IOC_DEVICES_READY (btrfs dev ready <dev>)
they have been unit tested to work fine with this patch.
If the user knows what he is doing and really want to pair with
replaced disk (which is not a standard operation), then he should
first clear the kernel btrfs device list in the memory by doing
the module unload/load and followed with the mount -o device option.
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/volumes.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 56822f0..bb1b4bd 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -523,6 +523,16 @@ static noinline int device_list_add(const char *path,
if (fs_devices->opened)
return -EBUSY;
+ else {
+ /*
+ * That is if the FS is _not_ mounted and if you are here, that
+ * means there is more than one disk with same uuid and devid.
+ * We keep the one with larger generation number or the last-in
+ * if generation are equal.
+ */
+ if (found_transid < device->generation)
+ return -EINVAL;
+ }
name = rcu_string_strdup(path, GFP_NOFS);
if (!name)
@@ -535,6 +545,15 @@ static noinline int device_list_add(const char *path,
}
}
+ /*
+ * Unmount does not free the btrfs_device struct but would zero
+ * generation along with most of the other members. So just update
+ * it back. We need it to pick the disk with largest generation
+ * (as above).
+ */
+ if (!fs_devices->opened)
+ device->generation = found_transid;
+
if (found_transid > fs_devices->latest_trans) {
fs_devices->latest_devid = devid;
fs_devices->latest_trans = found_transid;
--
1.8.5.3
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