Stefan Behrens
2012-Oct-30 17:16 UTC
[PATCH] Btrfs: don''t allow degraded mount if too many devices are missing
The current behavior is to allow mounting or remounting a filesystem
writeable in degraded mode if at least one writeable device is
present.
The next failed write access to a missing device which is above
the tolerance of the configured level of redundancy results in an
read-only enforcement. Even without this, the next time
barrier_all_devices() is called and more devices are missing than
tolerable, the switch to read-only mode takes place.
In order to behave predictably and to provide proper feedback to
the user at mount time, this patch compares the number of missing
devices with the number of devices that are tolerated to be missing
according to the configured RAID level. If more devices are missing
than tolerated, e.g. if two devices are missing in case of RAID1,
only a read-only mount and remount is allowed.
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
---
fs/btrfs/disk-io.c | 7 +++++++
fs/btrfs/super.c | 9 +++++++++
2 files changed, 16 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7cda519..29de7c1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2503,6 +2503,13 @@ retry_root_backup:
}
fs_info->num_tolerated_disk_barrier_failures
btrfs_calc_num_tolerated_disk_barrier_failures(fs_info);
+ if (fs_info->fs_devices->missing_devices >
+ fs_info->num_tolerated_disk_barrier_failures &&
+ !(sb->s_flags & MS_RDONLY)) {
+ printk(KERN_WARNING
+ "Btrfs: too many missing devices, writeable mount is not
allowed\n");
+ goto fail_block_groups;
+ }
fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
"btrfs-cleaner");
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 915ac14..acd2df8 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1226,6 +1226,15 @@ static int btrfs_remount(struct super_block *sb, int
*flags, char *data)
goto restore;
}
+ if (fs_info->fs_devices->missing_devices >
+ fs_info->num_tolerated_disk_barrier_failures &&
+ !(*flags & MS_RDONLY)) {
+ printk(KERN_WARNING
+ "Btrfs: too many missing devices, writeable remount is not
allowed\n");
+ ret = -EACCES;
+ goto restore;
+ }
+
if (btrfs_super_log_root(fs_info->super_copy) != 0) {
ret = -EINVAL;
goto restore;
--
1.8.0
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David Sterba
2012-Oct-31 00:07 UTC
Re: [PATCH] Btrfs: don''t allow degraded mount if too many devices are missing
Patch looks ok, juste one thing that caught my attention (and does not block
the patch)
a bit of context:
1224 if (fs_info->fs_devices->rw_devices == 0) {
1225 ret = -EACCES;
1226 goto restore;
1227 }
> + if (fs_info->fs_devices->missing_devices >
> + fs_info->num_tolerated_disk_barrier_failures &&
> + !(*flags & MS_RDONLY)) {
> + printk(KERN_WARNING
> + "Btrfs: too many missing devices, writeable remount is not
allowed\n");
> + ret = -EACCES;
the error code is strange, but it also appears above and has been there for
ages. We''re not checking any sort of permissions so this looks
confusing,
probably EINVAL or EPERM ?
> + goto restore;
> + }
> +
> if (btrfs_super_log_root(fs_info->super_copy) != 0) {
> ret = -EINVAL;
> goto restore;
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