Re: [PATCH 4/5] libxfs: Catch non-empty zones on destroy

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Mar 06, 2018 at 03:56:11PM -0600, Eric Sandeen wrote:
> Create and use a kmem_zone_destroy which warns if we are
> releasing a non-empty zone when the LIBXFS_LEAK_CHECK
> environment variable is set, wire this into libxfs_destroy(),
> and call that when various tools exit.
> 
> The LIBXFS_LEAK_CHECK environment variable also causes
> the program to exit with failure when a leak is detected,
> useful for failing automated tests if leaks are encountered.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
>  include/kmem.h |  1 +
>  libxfs/init.c  | 36 +++++++++++++++++++++++-------------
>  libxfs/kmem.c  | 14 ++++++++++++++
>  3 files changed, 38 insertions(+), 13 deletions(-)
> 
> diff --git a/include/kmem.h b/include/kmem.h
> index 65f0ade..572a4fa 100644
> --- a/include/kmem.h
> +++ b/include/kmem.h
> @@ -33,6 +33,7 @@ typedef struct kmem_zone {
>  extern kmem_zone_t *kmem_zone_init(int, char *);
>  extern void	*kmem_zone_alloc(kmem_zone_t *, int);
>  extern void	*kmem_zone_zalloc(kmem_zone_t *, int);
> +extern int	kmem_zone_destroy(kmem_zone_t *);
>  
>  static inline void
>  kmem_zone_free(kmem_zone_t *zone, void *ptr)
> diff --git a/libxfs/init.c b/libxfs/init.c
> index 3456cb5..a65c86c 100644
> --- a/libxfs/init.c
> +++ b/libxfs/init.c
> @@ -43,7 +43,7 @@ int libxfs_bhash_size;		/* #buckets in bcache */
>  
>  int	use_xfs_buf_lock;	/* global flag: use xfs_buf_t locks for MT */
>  
> -static void manage_zones(int);	/* setup global zones */
> +static int manage_zones(int);	/* setup/teardown global zones */

Returns what?  Number of leaked objects?

Oh, 1 if leaks and 0 if no leaks.

>  
>  /*
>   * dev_map - map open devices to fd.
> @@ -372,7 +372,7 @@ done:
>  /*
>   * Initialize/destroy all of the zone allocators we use.
>   */
> -static void
> +static int
>  manage_zones(int release)
>  {
>  	extern kmem_zone_t	*xfs_buf_zone;
> @@ -388,16 +388,20 @@ manage_zones(int release)
>  	extern void		xfs_dir_startup();
>  
>  	if (release) {	/* free zone allocation */
> -		kmem_free(xfs_buf_zone);
> -		kmem_free(xfs_inode_zone);
> -		kmem_free(xfs_ifork_zone);
> -		kmem_free(xfs_buf_item_zone);
> -		kmem_free(xfs_da_state_zone);
> -		kmem_free(xfs_btree_cur_zone);
> -		kmem_free(xfs_bmap_free_item_zone);
> -		kmem_free(xfs_trans_zone);
> -		kmem_free(xfs_log_item_desc_zone);
> -		return;
> +		int	leaked = 0;
> +
> +		leaked += kmem_zone_destroy(xfs_buf_zone);
> +		leaked += kmem_zone_destroy(xfs_ili_zone);
> +		leaked += kmem_zone_destroy(xfs_inode_zone);
> +		leaked += kmem_zone_destroy(xfs_ifork_zone);
> +		leaked += kmem_zone_destroy(xfs_buf_item_zone);
> +		leaked += kmem_zone_destroy(xfs_da_state_zone);
> +		leaked += kmem_zone_destroy(xfs_btree_cur_zone);
> +		leaked += kmem_zone_destroy(xfs_bmap_free_item_zone);
> +		leaked += kmem_zone_destroy(xfs_trans_zone);
> +		leaked += kmem_zone_destroy(xfs_log_item_desc_zone);
> +
> +		return leaked;
>  	}
>  	/* otherwise initialise zone allocation */
>  	xfs_buf_zone = kmem_zone_init(sizeof(xfs_buf_t), "xfs_buffer");
> @@ -419,6 +423,8 @@ manage_zones(int release)
>  	xfs_log_item_desc_zone = kmem_zone_init(
>  			sizeof(struct xfs_log_item_desc), "xfs_log_item_desc");
>  	xfs_dir_startup();
> +
> +	return 0;
>  }
>  
>  /*
> @@ -887,11 +893,15 @@ libxfs_umount(xfs_mount_t *mp)
>  void
>  libxfs_destroy(void)
>  {
> +	int	leaked;
> +
>  	/* Free everything from the buffer cache before freeing buffer zone */
>  	libxfs_bcache_purge();
>  	libxfs_bcache_free();
>  	cache_destroy(libxfs_bcache);
> -	manage_zones(1);
> +	leaked = manage_zones(1);
> +	if (getenv("LIBXFS_LEAK_CHECK") && leaked)
> +		exit(1);

What do you think of assert(getenv() == NULL || !leaked); here?
LIBXFS_LEAK_CHECK is a debugging option, so we might as well dump core
right where we violate the assumptions.

(OTOH I guess this probably happens at program exit anyway...)

>  }
>  
>  int
> diff --git a/libxfs/kmem.c b/libxfs/kmem.c
> index c8bcb50..a1f64e5 100644
> --- a/libxfs/kmem.c
> +++ b/libxfs/kmem.c
> @@ -23,6 +23,20 @@ kmem_zone_init(int size, char *name)
>  	return ptr;
>  }
>  
> +int
> +kmem_zone_destroy(kmem_zone_t *zone)
> +{
> +	int	leaked = 0;
> +
> +	if (getenv("LIBXFS_LEAK_CHECK") && zone->allocated) {
> +		leaked = 1;
> +		printf("zone %s freed with %d items allocated\n",
> +				zone->zone_name, zone->allocated);

fprintf(stderr, ...)?  Since leaking /is/ an error.

--D

> +	}
> +	free(zone);
> +	return leaked;
> +}
> +
>  void *
>  kmem_zone_alloc(kmem_zone_t *zone, int flags)
>  {
> -- 
> 1.8.3.1
> 
> 
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