Re: [PATCH 10/10] xfs_repair: add AG btree rmaps into the filesystem after syncing sb

From: Eric Sandeen <sandeen@sandeen.net>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 10/10] xfs_repair: add AG btree rmaps into the filesystem after syncing sb
Date: Mon, 9 Sep 2019 14:28:26 -0500	[thread overview]
Message-ID: <0e2cff80-832e-4a61-c378-f0b9515895e4@sandeen.net> (raw)
In-Reply-To: <156757189224.1838441.6843620202811391667.stgit@magnolia>

On 9/3/19 11:38 PM, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> In rmap_store_ag_btree_rec(), we try to reserve 16 blocks to handle
> adding all the AG btree rmaps to the rmap record.  Unfortunately, at
> that point in phase5 we haven't yet reinitialied sb_fdblocks, so
> reserving blocks can fail if repair reconstructed the primary sb from a
> secondary sb.  Even if the function succeeds, this still leads to
> incorrect fdblocks because phase 5 resets sb_fdblocks after running the
> rmap transactions.
> 
> To avoid all this, move the rmap_store_ag_btree_rec call to after the sb
> has been reset.  xfs/350 was helpful in finding cases where xfs_repair
> errored out while repairing the filesystem.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

makes sense to me; would be nice to know what this failure looks like at
repair time tho, for inclusion in the changelog, perhaps.

Reviewed-by: Eric Sandeen <sandeen@redhat.com>

> ---
>  repair/phase5.c |   24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> 
> diff --git a/repair/phase5.c b/repair/phase5.c
> index 2e18cc69..7f7d3d18 100644
> --- a/repair/phase5.c
> +++ b/repair/phase5.c
> @@ -2233,7 +2233,6 @@ phase5_func(
>  #endif
>  	xfs_agblock_t	num_extents;
>  	struct agi_stat	agi_stat = {0,};
> -	int		error;
>  
>  	if (verbose)
>  		do_log(_("        - agno = %d\n"), agno);
> @@ -2426,14 +2425,6 @@ phase5_func(
>  			finish_cursor(&fino_btree_curs);
>  		finish_cursor(&bcnt_btree_curs);
>  
> -		/*
> -		 * Put the per-AG btree rmap data into the rmapbt
> -		 */
> -		error = rmap_store_ag_btree_rec(mp, agno);
> -		if (error)
> -			do_error(
> -_("unable to add AG %u reverse-mapping data to btree.\n"), agno);
> -
>  		/*
>  		 * release the incore per-AG bno/bcnt trees so
>  		 * the extent nodes can be recycled
> @@ -2561,6 +2552,21 @@ phase5(xfs_mount_t *mp)
>  	 */
>  	sync_sb(mp);
>  
> +	/*
> +	 * Put the per-AG btree rmap data into the rmapbt now that we've reset
> +	 * the superblock counters.
> +	 */
> +	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
> +		error = rmap_store_ag_btree_rec(mp, agno);
> +		if (error)
> +			do_error(
> +_("unable to add AG %u reverse-mapping data to btree.\n"), agno);
> +	}
> +
> +	/*
> +	 * Put blocks that were unnecessarily reserved for btree
> +	 * reconstruction back into the filesystem free space data.
> +	 */
>  	error = inject_lost_blocks(mp, lost_fsb);
>  	if (error)
>  		do_error(_("Unable to reinsert lost blocks into filesystem.\n"));
> 