Commit 292fd7fc authored Oct 30, 2012 by Stefan Behrens Committed by Josef Bacik Dec 12, 2012

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>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

parent d1423248

fs/btrfs/disk-io.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -2508,6 +2508,13 @@ 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");

fs/btrfs/super.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -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;

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