xfs: allow sysadmins to specify a maximum atomic write limit at mount time

Introduce a mount option to allow sysadmins to specify the maximum size
of an atomic write.  If the filesystem can work with the supplied value,
that becomes the new guaranteed maximum.

The value mustn't be too big for the existing filesystem geometry (max
write size, max AG/rtgroup size).  We dynamically recompute the
tr_atomic_write transaction reservation based on the given block size,
check that the current log size isn't less than the new minimum log size
constraints, and set a new maximum.

The actual software atomic write max is still computed based off of
tr_atomic_ioend the same way it has for the past few commits.  Note also
that xfs_calc_atomic_write_log_geometry is non-static because mkfs will
need that.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>

1 files changed, 57 insertions, 1 deletions

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 77a3c003fc4f..8e3ae1749855 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -111,7 +111,7 @@ enum {
 	Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
 	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
 	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_max_open_zones,
-	Opt_lifetime, Opt_nolifetime,
+	Opt_lifetime, Opt_nolifetime, Opt_max_atomic_write,
 };
 
 static const struct fs_parameter_spec xfs_fs_parameters[] = {
@@ -159,6 +159,7 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
 	fsparam_u32("max_open_zones",	Opt_max_open_zones),
 	fsparam_flag("lifetime",	Opt_lifetime),
 	fsparam_flag("nolifetime",	Opt_nolifetime),
+	fsparam_string("max_atomic_write",	Opt_max_atomic_write),
 	{}
 };
 
@@ -241,6 +242,9 @@ xfs_fs_show_options(
 
 	if (mp->m_max_open_zones)
 		seq_printf(m, ",max_open_zones=%u", mp->m_max_open_zones);
+	if (mp->m_awu_max_bytes)
+		seq_printf(m, ",max_atomic_write=%lluk",
+				mp->m_awu_max_bytes >> 10);
 
 	return 0;
 }
@@ -1343,6 +1347,42 @@ suffix_kstrtoint(
 	return ret;
 }
 
+static int
+suffix_kstrtoull(
+	const char		*s,
+	unsigned int		base,
+	unsigned long long	*res)
+{
+	int			last, shift_left_factor = 0;
+	unsigned long long	_res;
+	char			*value;
+	int			ret = 0;
+
+	value = kstrdup(s, GFP_KERNEL);
+	if (!value)
+		return -ENOMEM;
+
+	last = strlen(value) - 1;
+	if (value[last] == 'K' || value[last] == 'k') {
+		shift_left_factor = 10;
+		value[last] = '\0';
+	}
+	if (value[last] == 'M' || value[last] == 'm') {
+		shift_left_factor = 20;
+		value[last] = '\0';
+	}
+	if (value[last] == 'G' || value[last] == 'g') {
+		shift_left_factor = 30;
+		value[last] = '\0';
+	}
+
+	if (kstrtoull(value, base, &_res))
+		ret = -EINVAL;
+	kfree(value);
+	*res = _res << shift_left_factor;
+	return ret;
+}
+
 static inline void
 xfs_fs_warn_deprecated(
 	struct fs_context	*fc,
@@ -1527,6 +1567,14 @@ xfs_fs_parse_param(
 	case Opt_nolifetime:
 		parsing_mp->m_features |= XFS_FEAT_NOLIFETIME;
 		return 0;
+	case Opt_max_atomic_write:
+		if (suffix_kstrtoull(param->string, 10,
+				     &parsing_mp->m_awu_max_bytes)) {
+			xfs_warn(parsing_mp,
+ "max atomic write size must be positive integer");
+			return -EINVAL;
+		}
+		return 0;
 	default:
 		xfs_warn(parsing_mp, "unknown mount option [%s].", param->key);
 		return -EINVAL;
@@ -2137,6 +2185,14 @@ xfs_fs_reconfigure(
 	if (error)
 		return error;
 
+	/* Validate new max_atomic_write option before making other changes */
+	if (mp->m_awu_max_bytes != new_mp->m_awu_max_bytes) {
+		error = xfs_set_max_atomic_write_opt(mp,
+				new_mp->m_awu_max_bytes);
+		if (error)
+			return error;
+	}
+
 	/* inode32 -> inode64 */
 	if (xfs_has_small_inums(mp) && !xfs_has_small_inums(new_mp)) {
 		mp->m_features &= ~XFS_FEAT_SMALL_INUMS;