Re: [PATCH 06/10] xfs_repair: clear the needsrepair flag

[Brian Foster <bfoster@redhat.com>]

On Mon, Feb 08, 2021 at 08:10:38PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Clear the needsrepair flag, since it's used to prevent mounting of an
> inconsistent filesystem.  We only do this if we make it to the end of
> repair with a non-zero error code, and all the rebuilt indices and
> corrected metadata are persisted correctly.
> 
> Note that we cannot combine clearing needsrepair with clearing the quota
> checked flags because we need to clear the quota flags even if
> reformatting the log fails, whereas we can't clear needsrepair if the
> log reformat fails.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  include/xfs_mount.h |    1 +
>  libxfs/init.c       |   25 +++++++++++++------------
>  repair/agheader.c   |   21 +++++++++++++++++++++
>  repair/xfs_repair.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 80 insertions(+), 12 deletions(-)
> 
> 
...
> diff --git a/libxfs/init.c b/libxfs/init.c
> index 9fe13b8d..98057b78 100644
> --- a/libxfs/init.c
> +++ b/libxfs/init.c
> @@ -867,25 +867,17 @@ _("%s: Flushing the %s failed, err=%d!\n"),
>  }
>  
>  /*
> - * Flush all dirty buffers to stable storage and report on writes that didn't
> - * make it to stable storage.
> + * Persist all disk write caches and report on writes that didn't make it to
> + * stable storage.  Callers should flush (or purge) the libxfs buffer caches
> + * before calling this function.
>   */
> -static int
> +int
>  libxfs_flush_mount(
>  	struct xfs_mount	*mp)
>  {
>  	int			error = 0;
>  	int			err2;
>  
> -	/*
> -	 * Purge the buffer cache to write all dirty buffers to disk and free
> -	 * all incore buffers.  Buffers that fail write verification will cause
> -	 * the CORRUPT_WRITE flag to be set in the buftarg.  Buffers that
> -	 * cannot be written will cause the LOST_WRITE flag to be set in the
> -	 * buftarg.
> -	 */
> -	libxfs_bcache_purge();
> -

FWIW, my comment on the previous version was that I think it's
reasonable to call libxfs_bcache_flush() here instead of the purge so
callers don't necessarily have to do anything special. The one caller
that does the purge is free to do so before calling
libxfs_flush_mount(), as that essentially supercedes the flush that
would otherwise occur here. Either way, the patch looks fine to me:

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  	/* Flush all kernel and disk write caches, and report failures. */
>  	if (mp->m_ddev_targp) {
>  		err2 = libxfs_flush_buftarg(mp->m_ddev_targp, _("data device"));
> @@ -923,6 +915,15 @@ libxfs_umount(
>  
>  	libxfs_rtmount_destroy(mp);
>  
> +	/*
> +	 * Purge the buffer cache to write all dirty buffers to disk and free
> +	 * all incore buffers.  Buffers that fail write verification will cause
> +	 * the CORRUPT_WRITE flag to be set in the buftarg.  Buffers that
> +	 * cannot be written will cause the LOST_WRITE flag to be set in the
> +	 * buftarg.  Once that's done, instruct the disks to persist their
> +	 * write caches.
> +	 */
> +	libxfs_bcache_purge();
>  	error = libxfs_flush_mount(mp);
>  
>  	for (agno = 0; agno < mp->m_maxagi; agno++) {
> diff --git a/repair/agheader.c b/repair/agheader.c
> index 8bb99489..2af24106 100644
> --- a/repair/agheader.c
> +++ b/repair/agheader.c
> @@ -452,6 +452,27 @@ secondary_sb_whack(
>  			rval |= XR_AG_SB_SEC;
>  	}
>  
> +	if (xfs_sb_version_needsrepair(sb)) {
> +		if (i == 0) {
> +			if (!no_modify)
> +				do_warn(
> +	_("clearing needsrepair flag and regenerating metadata\n"));
> +			else
> +				do_warn(
> +	_("would clear needsrepair flag and regenerate metadata\n"));
> +		} else {
> +			/*
> +			 * Quietly clear needsrepair on the secondary supers as
> +			 * part of ensuring them.  If needsrepair is set on the
> +			 * primary, it will be cleared at the end of repair
> +			 * once we've flushed all other dirty blocks to disk.
> +			 */
> +			sb->sb_features_incompat &=
> +					~XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
> +			rval |= XR_AG_SB_SEC;
> +		}
> +	}
> +
>  	return(rval);
>  }
>  
> diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
> index 32755821..f607afcb 100644
> --- a/repair/xfs_repair.c
> +++ b/repair/xfs_repair.c
> @@ -712,6 +712,48 @@ check_fs_vs_host_sectsize(
>  	}
>  }
>  
> +/* Clear needsrepair after a successful repair run. */
> +void
> +clear_needsrepair(
> +	struct xfs_mount	*mp)
> +{
> +	struct xfs_buf		*bp;
> +	int			error;
> +
> +	/*
> +	 * If we're going to clear NEEDSREPAIR, we need to make absolutely sure
> +	 * that everything is ok with the ondisk filesystem.  At this point
> +	 * we've flushed the filesystem metadata out of the buffer cache and
> +	 * possibly rewrote the log, but we haven't forced the disks to persist
> +	 * the writes to stable storage.  Do that now, and if anything goes
> +	 * wrong, leave NEEDSREPAIR in place.  Don't purge the buffer cache
> +	 * here since we're not done yet.
> +	 */
> +	libxfs_bcache_flush();
> +	error = -libxfs_flush_mount(mp);
> +	if (error) {
> +		do_warn(
> +	_("Cannot clear needsrepair due to flush failure, err=%d.\n"),
> +			error);
> +		return;
> +	}
> +
> +	/* Clear needsrepair from the superblock. */
> +	bp = libxfs_getsb(mp);
> +	if (!bp || bp->b_error) {
> +		do_warn(
> +	_("Cannot clear needsrepair from primary super, err=%d.\n"),
> +			bp ? bp->b_error : ENOMEM);
> +	} else {
> +		mp->m_sb.sb_features_incompat &=
> +				~XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
> +		libxfs_sb_to_disk(bp->b_addr, &mp->m_sb);
> +		libxfs_buf_mark_dirty(bp);
> +	}
> +	if (bp)
> +		libxfs_buf_relse(bp);
> +}
> +
>  int
>  main(int argc, char **argv)
>  {
> @@ -1131,6 +1173,9 @@ _("Note - stripe unit (%d) and width (%d) were copied from a backup superblock.\
>  	libxfs_bcache_flush();
>  	format_log_max_lsn(mp);
>  
> +	if (xfs_sb_version_needsrepair(&mp->m_sb))
> +		clear_needsrepair(mp);
> +
>  	/* Report failure if anything failed to get written to our fs. */
>  	error = -libxfs_umount(mp);
>  	if (error)
>