Re: [RFC PATCH v3 9/9] xfs: Implement ->corrupted_range() for XFS

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

On Tue, Dec 15, 2020 at 08:14:14PM +0800, Shiyang Ruan wrote:
> This function is used to handle errors which may cause data lost in
> filesystem.  Such as memory failure in fsdax mode.
> 
> In XFS, it requires "rmapbt" feature in order to query for files or
> metadata which associated to the corrupted data.  Then we could call fs
> recover functions to try to repair the corrupted data.(did not
> implemented in this patchset)
> 
> After that, the memory failure also needs to notify the processes who
> are using those files.
> 
> Only support data device.  Realtime device is not supported for now.
> 
> Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
> ---
>  fs/xfs/xfs_fsops.c | 10 +++++
>  fs/xfs/xfs_mount.h |  2 +
>  fs/xfs/xfs_super.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 105 insertions(+)
> 
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index ef1d5bb88b93..0ec1b44bfe88 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -501,6 +501,16 @@ xfs_do_force_shutdown(
>  "Corruption of in-memory data detected.  Shutting down filesystem");
>  		if (XFS_ERRLEVEL_HIGH <= xfs_error_level)
>  			xfs_stack_trace();
> +	} else if (flags & SHUTDOWN_CORRUPT_META) {
> +		xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_CORRUPT,
> +"Corruption of on-disk metadata detected.  Shutting down filesystem");
> +		if (XFS_ERRLEVEL_HIGH <= xfs_error_level)
> +			xfs_stack_trace();
> +	} else if (flags & SHUTDOWN_CORRUPT_DATA) {
> +		xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_CORRUPT,
> +"Corruption of on-disk file data detected.  Shutting down filesystem");
> +		if (XFS_ERRLEVEL_HIGH <= xfs_error_level)
> +			xfs_stack_trace();
>  	} else if (logerror) {
>  		xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_LOGERROR,
>  			"Log I/O Error Detected. Shutting down filesystem");
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index dfa429b77ee2..e36c07553486 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -274,6 +274,8 @@ void xfs_do_force_shutdown(struct xfs_mount *mp, int flags, char *fname,
>  #define SHUTDOWN_LOG_IO_ERROR	0x0002	/* write attempt to the log failed */
>  #define SHUTDOWN_FORCE_UMOUNT	0x0004	/* shutdown from a forced unmount */
>  #define SHUTDOWN_CORRUPT_INCORE	0x0008	/* corrupt in-memory data structures */
> +#define SHUTDOWN_CORRUPT_META	0x0010  /* corrupt metadata on device */
> +#define SHUTDOWN_CORRUPT_DATA	0x0020  /* corrupt file data on device */

This symbol isn't used anywhere.  I don't know why we'd shut down the fs
for data loss, as we don't do that anywhere else in xfs.

>  
>  /*
>   * Flags for xfs_mountfs
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index e3e229e52512..30202de7e89d 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -35,6 +35,11 @@
>  #include "xfs_refcount_item.h"
>  #include "xfs_bmap_item.h"
>  #include "xfs_reflink.h"
> +#include "xfs_alloc.h"
> +#include "xfs_rmap.h"
> +#include "xfs_rmap_btree.h"
> +#include "xfs_rtalloc.h"
> +#include "xfs_bit.h"
>  
>  #include <linux/magic.h>
>  #include <linux/fs_context.h>
> @@ -1103,6 +1108,93 @@ xfs_fs_free_cached_objects(
>  	return xfs_reclaim_inodes_nr(XFS_M(sb), sc->nr_to_scan);
>  }
>  
> +static int
> +xfs_corrupt_helper(
> +	struct xfs_btree_cur		*cur,
> +	struct xfs_rmap_irec		*rec,
> +	void				*data)
> +{
> +	struct xfs_inode		*ip;
> +	int				rc = 0;

Note: we usually use the name "error", not "rc".

> +	int				*flags = data;
> +
> +	if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner)) {

There are a few more things to check here to detect if metadata has been
lost.  The first is that any loss in the extended attribute information
is considered filesystem metadata; and the second is that loss of an
extent btree block is also metadata.

IOWs, this check should be:

	if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) ||
	    (rec->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK))) {
		// TODO check and try to fix metadata
		return -EFSCORRUPTED;
	}

> +		// TODO check and try to fix metadata
> +		rc = -EFSCORRUPTED;
> +	} else {
> +		/*
> +		 * Get files that incore, filter out others that are not in use.
> +		 */
> +		rc = xfs_iget(cur->bc_mp, cur->bc_tp, rec->rm_owner,
> +			      XFS_IGET_INCORE, 0, &ip);
> +		if (rc || !ip)
> +			return rc;
> +		if (!VFS_I(ip)->i_mapping)
> +			goto out;
> +
> +		if (IS_DAX(VFS_I(ip)))
> +			rc = mf_dax_mapping_kill_procs(VFS_I(ip)->i_mapping,
> +						       rec->rm_offset, *flags);

If the file isn't S_DAX, should we call mapping_set_error here so
that the next fsync() will also return EIO?

> +
> +		// TODO try to fix data
> +out:
> +		xfs_irele(ip);
> +	}
> +
> +	return rc;
> +}
> +
> +static int
> +xfs_fs_corrupted_range(
> +	struct super_block	*sb,
> +	struct block_device	*bdev,
> +	loff_t			offset,
> +	size_t			len,
> +	void			*data)
> +{
> +	struct xfs_mount	*mp = XFS_M(sb);
> +	struct xfs_trans	*tp = NULL;
> +	struct xfs_btree_cur	*cur = NULL;
> +	struct xfs_rmap_irec	rmap_low, rmap_high;
> +	struct xfs_buf		*agf_bp = NULL;
> +	xfs_fsblock_t		fsbno = XFS_B_TO_FSB(mp, offset);
> +	xfs_filblks_t		bc = XFS_B_TO_FSB(mp, len);
> +	xfs_agnumber_t		agno = XFS_FSB_TO_AGNO(mp, fsbno);
> +	xfs_agblock_t		agbno = XFS_FSB_TO_AGBNO(mp, fsbno);
> +	int			rc = 0;
> +
> +	if (mp->m_rtdev_targp && mp->m_rtdev_targp->bt_bdev == bdev) {
> +		xfs_warn(mp, "storage lost support not available for realtime device!");
> +		return 0;
> +	}

This ought to kill the fs when an external log device is configured:

	if (mp->m_logdev_targp &&
	    mp->m_logdev_targp != mp->m_ddev_targp &&
	    mp->m_logdev_targp->bt_bdev == bdev) {
		xfs_error(mp, "ondisk log corrupt, shutting down fs!");
		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_META);
		return 0;
	}

Then, we need to check explicitly for rmap support:

	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
		return 0;

so that we screen out filesystems that don't have rmap enabled.

> +	rc = xfs_trans_alloc_empty(mp, &tp);
> +	if (rc)
> +		return rc;
> +
> +	rc = xfs_alloc_read_agf(mp, tp, agno, 0, &agf_bp);
> +	if (rc)
> +		return rc;
> +
> +	cur = xfs_rmapbt_init_cursor(mp, tp, agf_bp, agno);
> +
> +	/* Construct a range for rmap query */
> +	memset(&rmap_low, 0, sizeof(rmap_low));
> +	memset(&rmap_high, 0xFF, sizeof(rmap_high));
> +	rmap_low.rm_startblock = rmap_high.rm_startblock = agbno;
> +	rmap_low.rm_blockcount = rmap_high.rm_blockcount = bc;
> +
> +	rc = xfs_rmap_query_range(cur, &rmap_low, &rmap_high, xfs_corrupt_helper, data);
> +	if (rc == -ECANCELED)
> +		rc = 0;

I don't think anything returns ECANCELED here...

--D

> +	if (rc == -EFSCORRUPTED)
> +		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_META);
> +
> +	xfs_btree_del_cursor(cur, rc);
> +	xfs_trans_brelse(tp, agf_bp);
> +	return rc;
> +}
> +
>  static const struct super_operations xfs_super_operations = {
>  	.alloc_inode		= xfs_fs_alloc_inode,
>  	.destroy_inode		= xfs_fs_destroy_inode,
> @@ -1116,6 +1208,7 @@ static const struct super_operations xfs_super_operations = {
>  	.show_options		= xfs_fs_show_options,
>  	.nr_cached_objects	= xfs_fs_nr_cached_objects,
>  	.free_cached_objects	= xfs_fs_free_cached_objects,
> +	.corrupted_range	= xfs_fs_corrupted_range,
>  };
>  
>  static int
> -- 
> 2.29.2
> 
> 
>