Re: [PATCH V8 16/19] xfs: Conditionally upgrade existing inodes to use large extent counters

Dave Chinner
2022-03-24T22:28:16Z

On Mon, Mar 21, 2022 at 10:47:47AM +0530, Chandan Babu R wrote:
> This commit enables upgrading existing inodes to use large extent counters
> provided that underlying filesystem's superblock has large extent counter
> feature enabled.
>
> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
> ---
> fs/xfs/libxfs/xfs_attr.c | 9 ++++++-
> fs/xfs/libxfs/xfs_bmap.c | 10 ++++++--
> fs/xfs/libxfs/xfs_inode_fork.c | 27 +++++++++++++++++++++
> fs/xfs/libxfs/xfs_inode_fork.h | 2 ++
> fs/xfs/xfs_bmap_item.c | 8 ++++++-
> fs/xfs/xfs_bmap_util.c | 43 ++++++++++++++++++++++++++++++----
> fs/xfs/xfs_dquot.c | 9 ++++++-
> fs/xfs/xfs_iomap.c | 17 ++++++++++++--
> fs/xfs/xfs_reflink.c | 17 ++++++++++++--
> fs/xfs/xfs_rtalloc.c | 9 ++++++-
> 10 files changed, 136 insertions(+), 15 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 23523b802539..6e56aa17fd82 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -776,8 +776,15 @@ xfs_attr_set(
> if (args->value || xfs_inode_hasattr(dp)) {
> error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
> XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
> - if (error)
> + if (error && error != -EFBIG)
> goto out_trans_cancel;
> +
> + if (error == -EFBIG) {
> + error = xfs_iext_count_upgrade(args->trans, dp,
> + XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
> + if (error)
> + goto out_trans_cancel;
> + }

Neater and more compact to do this by checking explicitly for
-EFBIG:

error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
if (error == -EFBIG)
error = xfs_iext_count_upgrade(args->trans, dp,
XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
if (error)
goto out_trans_cancel;
}
>
> error = xfs_attr_lookup(args);
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 5a089674c666..0cb915bf8285 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -4524,13 +4524,19 @@ xfs_bmapi_convert_delalloc(
> return error;
>
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> + xfs_trans_ijoin(tp, ip, 0);
>
> error = xfs_iext_count_may_overflow(ip, whichfork,
> XFS_IEXT_ADD_NOSPLIT_CNT);
> - if (error)
> + if (error && error != -EFBIG)
> goto out_trans_cancel;
>
> - xfs_trans_ijoin(tp, ip, 0);
> + if (error == -EFBIG) {
> + error = xfs_iext_count_upgrade(tp, ip,
> + XFS_IEXT_ADD_NOSPLIT_CNT);
> + if (error)
> + goto out_trans_cancel;
> + }
>
> if (!xfs_iext_lookup_extent(ip, ifp, offset_fsb, &bma.icur, &bma.got) ||
> bma.got.br_startoff > offset_fsb) {
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index bb5d841aac58..aff9242db829 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -756,3 +756,30 @@ xfs_iext_count_may_overflow(
>
> return 0;
> }
> +
> +int
> +xfs_iext_count_upgrade(
> + struct xfs_trans *tp,
> + struct xfs_inode *ip,
> + int nr_to_add)

nr_to_add can only be positive, so should be unsigned.

> +{
> + if (!xfs_has_large_extent_counts(ip->i_mount) ||
> + (ip->i_diflags2 & XFS_DIFLAG2_NREXT64) ||
> + XFS_TEST_ERROR(false, ip->i_mount, XFS_ERRTAG_REDUCE_MAX_IEXTENTS))
> + return -EFBIG;
> +
> + ip->i_diflags2 |= XFS_DIFLAG2_NREXT64;
> + xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
> +
> + /*
> + * The value of nr_to_add cannot be larger than 2^17
> + *
> + * - XFS_MAX_EXTCNT_ATTR_FORK_LARGE - XFS_MAX_EXTCNT_ATTR_FORK_SMALL
> + * i.e. 2^32 - 2^15
> + * - XFS_MAX_EXTCNT_DATA_FORK_LARGE - XFS_MAX_EXTCNT_DATA_FORK_SMALL
> + * i.e. 2^48 - 2^31
> + */
> + ASSERT(nr_to_add <= (1 << 17));

That's a comment for the function head and/or the format
documentation in xfs_format.h, not hidden in the code itself as a
magic number. i.e. it is a format definition because it is bound by
on-disk format constants, not by code constratints. Hence this
should probably be defined in xfs_format.h alongside the large/small
extent counts, such as:

#define XFS_MAX_EXTCNT_UPGRADE_NR \
min(XFS_MAX_EXTCNT_ATTR_FORK_LARGE - XFS_MAX_EXTCNT_ATTR_FORK_SMALL, \
XFS_MAX_EXTCNT_DATA_FORK_LARGE - XFS_MAX_EXTCNT_DATA_FORK_SMALL)

And the ASSERT checking the incoming nr_to_add placed right at the
top of the function because the assert then documents API
constraints and always catches violations of them.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com