From 292fd7fc39aa06668f3a8db546714e727120cb3e Mon Sep 17 00:00:00 2001 From: Stefan Behrens Date: Tue, 30 Oct 2012 17:16:16 +0000 Subject: [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 Signed-off-by: Chris Mason --- 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 bd70c2852ba0..064315990f8a 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -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"); diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 915ac14c2064..acd2df85bed5 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; -- 2.20.1