[lxc-devel] [PATCH] lxc-destroy: actually work if underlying fs is overlayfs

[Stéphane Graber]

On Mon, Mar 16, 2015 at 05:02:12PM +0000, Serge Hallyn wrote:
> One of the 'features' of overlayfs is that depending on whether a file
> is on the upper or lower dir you get back a different device from stat.
> That breaks our lxc_rmdir_onedev.
> 
> So at lxc_rmdir_ondev check the device of the directory being deleted.
> If it is overlayfs, then skip the device check.
> 
> Note this is unrelated to overlayfs snapshots - in those cases when you
> delete a container, /var/lib/lxc/$container/ does not actually have an
> overlayfs under it.  Rather, to reproduce this you would
> 
> sudo mkdir /opt/{lower,upper,workdir}
> sudo mount -t overlayfs -o lower=/opt/lower,upper=/opt/upper,workdir=/opt/workdir \
> 	lxc /var/lib/lxc
> sudo lxc-create -t download -n c1 -- -d ubuntu -r trusty -a amd64
> sudo lxc-destroy -n c1
> 
> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>

Acked-by: Stéphane Graber <stgraber at ubuntu.com>

> ---
>  src/lxc/utils.c | 39 ++++++++++++++++++++++++++++++++-------
>  1 file changed, 32 insertions(+), 7 deletions(-)
> 
> diff --git a/src/lxc/utils.c b/src/lxc/utils.c
> index e66a01f..83020ad 100644
> --- a/src/lxc/utils.c
> +++ b/src/lxc/utils.c
> @@ -29,6 +29,7 @@
>  #include <stddef.h>
>  #include <string.h>
>  #include <sys/types.h>
> +#include <sys/vfs.h>
>  #include <sys/stat.h>
>  #include <sys/mman.h>
>  #include <sys/param.h>
> @@ -68,8 +69,8 @@
>  
>  lxc_log_define(lxc_utils, lxc);
>  
> -static int _recursive_rmdir_onedev(char *dirname, dev_t pdev,
> -				   const char *exclude, int level)
> +static int _recursive_rmdir(char *dirname, dev_t pdev,
> +			    const char *exclude, int level, bool onedev)
>  {
>  	struct dirent dirent, *direntp;
>  	DIR *dir;
> @@ -106,7 +107,7 @@ static int _recursive_rmdir_onedev(char *dirname, dev_t pdev,
>  			if (ret < 0) {
>  				switch(errno) {
>  				case ENOTEMPTY:
> -					INFO("Not deleting snapshots");
> +					INFO("Not deleting snapshot %s", pathname);
>  					hadexclude = true;
>  					break;
>  				case ENOTDIR:
> @@ -129,14 +130,14 @@ static int _recursive_rmdir_onedev(char *dirname, dev_t pdev,
>  			failed=1;
>  			continue;
>  		}
> -		if (mystat.st_dev != pdev)
> +		if (onedev && mystat.st_dev != pdev)
>  			continue;
>  		if (S_ISDIR(mystat.st_mode)) {
> -			if (_recursive_rmdir_onedev(pathname, pdev, exclude, level+1) < 0)
> +			if (_recursive_rmdir(pathname, pdev, exclude, level+1, onedev) < 0)
>  				failed=1;
>  		} else {
>  			if (unlink(pathname) < 0) {
> -				ERROR("%s: failed to delete %s", __func__, pathname);
> +				SYSERROR("%s: failed to delete %s", __func__, pathname);
>  				failed=1;
>  			}
>  		}
> @@ -158,17 +159,41 @@ static int _recursive_rmdir_onedev(char *dirname, dev_t pdev,
>  	return failed ? -1 : 0;
>  }
>  
> +/* we have two different magic values for overlayfs, yay */
> +#define OVERLAYFS_SUPER_MAGIC 0x794c764f
> +#define OVERLAY_SUPER_MAGIC 0x794c7630
> +/*
> + * In overlayfs, st_dev is unreliable.  so on overlayfs we don't do
> + * the lxc_rmdir_onedev()
> + */
> +static bool is_native_overlayfs(const char *path)
> +{
> +	struct statfs sb;
> +
> +	if (statfs(path, &sb) < 0)
> +		return false;
> +	if (sb.f_type == OVERLAYFS_SUPER_MAGIC ||
> +			sb.f_type == OVERLAY_SUPER_MAGIC)
> +		return true;
> +	return false;
> +}
> +
>  /* returns 0 on success, -1 if there were any failures */
>  extern int lxc_rmdir_onedev(char *path, const char *exclude)
>  {
>  	struct stat mystat;
> +	bool onedev = true;
> +
> +	if (is_native_overlayfs(path)) {
> +		onedev = false;
> +	}
>  
>  	if (lstat(path, &mystat) < 0) {
>  		ERROR("%s: failed to stat %s", __func__, path);
>  		return -1;
>  	}
>  
> -	return _recursive_rmdir_onedev(path, mystat.st_dev, exclude, 0);
> +	return _recursive_rmdir(path, mystat.st_dev, exclude, 0, onedev);
>  }
>  
>  static int mount_fs(const char *source, const char *target, const char *type)
> -- 
> 2.1.4
> 
> _______________________________________________
> lxc-devel mailing list
> lxc-devel at lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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