On Fri, Jun 07, 2013 at 04:27:50AM -0600, Stefan Behrens wrote:
> When the UUID tree is initially created, a task is spawned that
> walks through the root tree. For each found subvolume root_item,
> the uuid and received_uuid entries in the UUID tree are added.
> This is such a quick operation so that in case somebody wants
> to unmount the filesystem while the task is still running, the
> unmount is delayed until the UUID tree building task is finished.
>
What if we crash? Then we'll think we have a perfectly good uuid tree when its
half full.
> Signed-off-by: Stefan Behrens <sbehrens@xxxxxxxxxxxxxxxx>
> ---
> fs/btrfs/ctree.h | 3 ++
> fs/btrfs/disk-io.c | 5 ++
> fs/btrfs/volumes.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 157 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index a635dbf..9393228 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -23,6 +23,7 @@
> #include <linux/highmem.h>
> #include <linux/fs.h>
> #include <linux/rwsem.h>
> +#include <linux/semaphore.h>
> #include <linux/completion.h>
> #include <linux/backing-dev.h>
> #include <linux/wait.h>
> @@ -1645,6 +1646,8 @@ struct btrfs_fs_info {
> struct btrfs_dev_replace dev_replace;
>
> atomic_t mutually_exclusive_operation_running;
> +
> + struct semaphore uuid_scan_sem;
> };
>
> /*
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 00bac63..89f99aa 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -31,6 +31,7 @@
> #include <linux/migrate.h>
> #include <linux/ratelimit.h>
> #include <linux/uuid.h>
> +#include <linux/semaphore.h>
> #include <asm/unaligned.h>
> #include "compat.h"
> #include "ctree.h"
> @@ -2288,6 +2289,7 @@ int open_ctree(struct super_block *sb,
> init_rwsem(&fs_info->extent_commit_sem);
> init_rwsem(&fs_info->cleanup_work_sem);
> init_rwsem(&fs_info->subvol_sem);
> + sema_init(&fs_info->uuid_scan_sem, 1);
> fs_info->dev_replace.lock_owner = 0;
> atomic_set(&fs_info->dev_replace.nesting_level, 0);
> mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount);
> @@ -3543,6 +3545,9 @@ int close_ctree(struct btrfs_root *root)
> fs_info->closing = 1;
> smp_mb();
>
> + /* wait for the uuid_scan task to finish */
> + down(&fs_info->uuid_scan_sem);
> +
Need to re-up it again right? Thanks,
Josef
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