Re: [PATCH 07/12] xfs: flush eof/cowblocks if we can't reserve quota for file blocks

[Brian Foster <bfoster@redhat.com>]

On Sun, Jan 31, 2021 at 06:06:06PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> If a fs modification (data write, reflink, xattr set, fallocate, etc.)
> is unable to reserve enough quota to handle the modification, try
> clearing whatever space the filesystem might have been hanging onto in
> the hopes of speeding up the filesystem.  The flushing behavior will
> become particularly important when we add deferred inode inactivation
> because that will increase the amount of space that isn't actively tied
> to user data.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---

(FWIW, I'm reviewing the patches from your reclaim-space-harder-5.12
branch as of this morning, which look like they have some deltas from
the posted versions based on Christoph's feedback.)

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

>  fs/xfs/xfs_reflink.c |    5 +++++
>  fs/xfs/xfs_trans.c   |   10 ++++++++++
>  2 files changed, 15 insertions(+)
> 
> 
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 086866f6e71f..725c7d8e4438 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1092,6 +1092,11 @@ xfs_reflink_remap_extent(
>  	 * count.  This is suboptimal, but the VFS flushed the dest range
>  	 * before we started.  That should have removed all the delalloc
>  	 * reservations, but we code defensively.
> +	 *
> +	 * xfs_trans_alloc_inode above already tried to grab an even larger
> +	 * quota reservation, and kicked off a blockgc scan if it couldn't.
> +	 * If we can't get a potentially smaller quota reservation now, we're
> +	 * done.
>  	 */
>  	if (!quota_reserved && !smap_real && dmap_written) {
>  		error = xfs_trans_reserve_quota_nblks(tp, ip,
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 466e1c86767f..f62c1c5f210f 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -23,6 +23,7 @@
>  #include "xfs_inode.h"
>  #include "xfs_dquot_item.h"
>  #include "xfs_dquot.h"
> +#include "xfs_icache.h"
>  
>  kmem_zone_t	*xfs_trans_zone;
>  
> @@ -1046,8 +1047,10 @@ xfs_trans_alloc_inode(
>  {
>  	struct xfs_trans	*tp;
>  	struct xfs_mount	*mp = ip->i_mount;
> +	bool			retried = false;
>  	int			error;
>  
> +retry:
>  	error = xfs_trans_alloc(mp, resv, dblocks,
>  			rblocks / mp->m_sb.sb_rextsize,
>  			force ? XFS_TRANS_RESERVE : 0, &tp);
> @@ -1065,6 +1068,13 @@ xfs_trans_alloc_inode(
>  	}
>  
>  	error = xfs_trans_reserve_quota_nblks(tp, ip, dblocks, rblocks, force);
> +	if (!retried && (error == -EDQUOT || error == -ENOSPC)) {
> +		xfs_trans_cancel(tp);
> +		xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +		xfs_blockgc_free_quota(ip, 0);
> +		retried = true;
> +		goto retry;
> +	}
>  	if (error)
>  		goto out_cancel;
>  
>