On 06/15/2012 03:49 PM, Alexander Block wrote:
> Before the update_time inode operation was indroduced, it was
> not possible to prevent updates of atime on RO subvolumes. VFS
> was only able to check for RO on the mount, but did not know
> anything about btrfs subvolumes.
>
> btrfs_update_time does now check if the root is RO and skip
> updating of times.
>
> Signed-off-by: Alexander Block <ablock84@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/inode.c | 5 +++++
> fs/inode.c | 2 ++
> 2 files changed, 7 insertions(+)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index f6ab6f5..4d0ceed 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4478,6 +4478,11 @@ int btrfs_dirty_inode(struct inode *inode)
> static int btrfs_update_time(struct inode *inode, struct timespec *now,
> int flags)
> {
> + struct btrfs_root *root = BTRFS_I(inode)->root;
> +
> + if (btrfs_root_readonly(root))
> + return -EROFS;
> +
It also needs to acquire root->fs_info->subvol_sem, doesn't it?
thanks,
liubo
> if (flags & S_VERSION)
> inode_inc_iversion(inode);
> if (flags & S_CTIME)
> diff --git a/fs/inode.c b/fs/inode.c
> index c99163b..033529e 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1551,6 +1551,8 @@ void touch_atime(struct path *path)
> * Btrfs), but since we touch atime while walking down the path we
> * really don't care if we failed to update the atime of the file,
> * so just ignore the return value.
> + * We may also fail on filesystems that have the ability to make parts
> + * of the fs read only, e.g. subvolumes in Btrfs.
> */
> update_time(inode, &now, S_ATIME);
> mnt_drop_write(mnt);
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