From: Anand Jain Date: Thu, 3 Jul 2014 10:22:06 +0000 (+0800) Subject: btrfs: check generation as replace duplicates devid+uuid X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=77bdae4d136e167bab028cbec58b988f91cf73c0;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git 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 ) 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 Signed-off-by: Wang Shilong Signed-off-by: Miao Xie Signed-off-by: Chris Mason --- diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 7c538f65214b..5700ab03e84b 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -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;