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Date:   Mon, 4 Jan 2021 15:21:59 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Shiyang Ruan <ruansy.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-raid@...r.kernel.org,
        dan.j.williams@...el.com, david@...morbit.com, hch@....de,
        song@...nel.org, rgoldwyn@...e.de, qi.fuli@...itsu.com,
        y-goto@...itsu.com
Subject: Re: [PATCH 09/10] xfs: Implement ->corrupted_range() for XFS

On Thu, Dec 31, 2020 at 12:56:00AM +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@...fujitsu.com>
> ---
>  fs/xfs/xfs_fsops.c |   5 +++
>  fs/xfs/xfs_mount.h |   1 +
>  fs/xfs/xfs_super.c | 107 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 113 insertions(+)
> 
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index ef1d5bb88b93..0a2038875d32 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -501,6 +501,11 @@ 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 (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..8f0df67ffcc1 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -274,6 +274,7 @@ 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 */
>  
>  /*
>   * Flags for xfs_mountfs
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index e3e229e52512..cbcad419bb9e 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 +1108,107 @@ 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;
> +	struct address_space		*mapping;
> +	int				rc = 0;
> +	int				*flags = data;
> +
> +	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
> +		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;
> +
> +		mapping = VFS_I(ip)->i_mapping;
> +		if (IS_DAX(VFS_I(ip)))
> +			rc = mf_dax_mapping_kill_procs(mapping, rec->rm_offset,
> +						       *flags);
> +		else
> +			mapping_set_error(mapping, -EFSCORRUPTED);

Hm.  I don't know if EFSCORRUPTED is the right error code for corrupt
file data, since we (so far) have only used it for corrupt metadata.

> +
> +		// 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		bcnt = 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			error = 0;
> +
> +	if (mp->m_rtdev_targp && mp->m_rtdev_targp->bt_bdev == bdev) {
> +		xfs_warn(mp, "corrupted_range support not available for realtime device!");
> +		return 0;
> +	}
> +	if (mp->m_logdev_targp && mp->m_logdev_targp->bt_bdev == bdev &&
> +	    mp->m_logdev_targp != mp->m_ddev_targp) {
> +		xfs_err(mp, "ondisk log corrupt, shutting down fs!");
> +		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_META);
> +		return 0;
> +	}
> +
> +	if (!xfs_sb_version_hasrmapbt(&mp->m_sb)) {
> +		xfs_warn(mp, "corrupted_range needs rmapbt enabled!");
> +		return 0;
> +	}
> +
> +	error = xfs_trans_alloc_empty(mp, &tp);
> +	if (error)
> +		return error;
> +
> +	error = xfs_alloc_read_agf(mp, tp, agno, 0, &agf_bp);
> +	if (error)
> +		return error;
> +
> +	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 = bcnt;
> +
> +	error = xfs_rmap_query_range(cur, &rmap_low, &rmap_high, xfs_corrupt_helper, data);
> +	if (error == -EFSCORRUPTED)
> +		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_META);
> +
> +	xfs_btree_del_cursor(cur, error);
> +	xfs_trans_brelse(tp, agf_bp);

The transaction needs to be committed (or cancelled) here, or else it
leaks.

--D

> +	return error;
> +}
> +
>  static const struct super_operations xfs_super_operations = {
>  	.alloc_inode		= xfs_fs_alloc_inode,
>  	.destroy_inode		= xfs_fs_destroy_inode,
> @@ -1116,6 +1222,7 @@ 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
> 
> 
> 

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