On Fri, Apr 08, 2016 at 03:23:28PM -0400, Austin S. Hemmelgarn wrote:
> On 2016-04-08 12:17, Chris Murphy wrote:
>
> I would personally suggest adding a per-filesystem node in sysfs to handle
> both 2 and 5. Having it open tells BTRFS to not automatically attempt
> countermeasures when degraded, select/epoll on it will return when state
> changes, reads will return (at minimum): what devices comprise the FS, per
> disk state (is it working, failed, missing, a hot-spare, etc), and what
> effective redundancy we have (how many devices we can lose and still be
> mountable, so 1 for raid1, raid10, and raid5, 2 for raid6, and 0 for
> raid0/single/dup, possibly higher for n-way replication (n-1), n-order
> parity (n), or erasure coding). This would make it trivial to write a daemon
> to monitor the filesystem, react when something happens, and handle all the
> policy decisions.
Hm, good proposal. Personally I tried to use uevents for this but they
cause locking troubles, and I didn't continue this attempt.
In any case we need have interface for btrfs-progs to passing FS state
information (presence and IDs of missing devices, for example,
degraded/good state of RAID etc.).
For testing as first attempt I implemented following interface. It still seems
not good for me but acceptable as a starting point. Additionally to this, I changed
missing device name reported in btrfs_ioctl_dev_info() to 'missing' for avoiding of
interferences with block devices inserted after closing of failed device (adding of
'missing' field to the struct btrfs_ioctl_dev_info_args may be more right way). So,
your opinion?
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d9b147f..f9a2fa6 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2716,12 +2716,17 @@ static long btrfs_ioctl_fs_info(struct btrfs_root *root, void __user *arg)
mutex_lock(&fs_devices->device_list_mutex);
fi_args->num_devices = fs_devices->num_devices;
+ fi_args->missing_devices = fs_devices->missing_devices;
+ fi_args->open_devices = fs_devices->open_devices;
+ fi_args->rw_devices = fs_devices->rw_devices;
+ fi_args->total_devices = fs_devices->total_devices;
memcpy(&fi_args->fsid, root->fs_info->fsid, sizeof(fi_args->fsid));
list_for_each_entry(device, &fs_devices->devices, dev_list) {
if (device->devid > fi_args->max_id)
fi_args->max_id = device->devid;
}
+ fi_args->state = root->fs_info->fs_state;
mutex_unlock(&fs_devices->device_list_mutex);
fi_args->nodesize = root->fs_info->super_copy->nodesize;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index dea8931..6808bf2 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -186,8 +186,12 @@ struct btrfs_ioctl_fs_info_args {
__u32 nodesize; /* out */
__u32 sectorsize; /* out */
__u32 clone_alignment; /* out */
- __u32 reserved32;
- __u64 reserved[122]; /* pad to 1k */
+ __u32 state; /* out */
+ __u64 missing_devices; /* out */
+ __u64 open_devices; /* out */
+ __u64 rw_devices; /* out */
+ __u64 total_devices; /* out */
+ __u64 reserved[118]; /* pad to 1k */
};
struct btrfs_ioctl_feature_flags {
--
Yauhen Kharuzhy
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