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btrfs: check generation as replace duplicates devid+uuid 

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@oracle.com>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Anand Jain 2014-07-03 18:22:06 +08:00 committed by Chris Mason
parent b96de000bc
commit 77bdae4d13
1 changed files with 21 additions and 1 deletions
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22
fs/btrfs/volumes.c
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@ -532,8 +532,19 @@ static noinline int device_list_add(const char *path,
* As of now don't allow update to btrfs_fs_device through
* the btrfs dev scan cli, after FS has been mounted.
*/
if (fs_devices->opened)
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 -EEXIST;
}
name = rcu_string_strdup(path, GFP_NOFS);
if (!name)
@ -546,6 +557,15 @@ 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;