[PATCH 08/20] xfs: expose sysfs knob to control inode inactivation delay

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Allow administrators to control the length that we defer inode
inactivation.  By default we'll set the delay to 5 seconds, as an
arbitrary choice between allowing for some batching of a deltree
operation, and not letting too many inodes pile up in memory.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 Documentation/admin-guide/xfs.rst |    7 +++++++
 fs/xfs/xfs_globals.c              |    5 +++++
 fs/xfs/xfs_icache.c               |    6 +++++-
 fs/xfs/xfs_linux.h                |    1 +
 fs/xfs/xfs_sysctl.c               |    9 +++++++++
 fs/xfs/xfs_sysctl.h               |    1 +
 6 files changed, 28 insertions(+), 1 deletion(-)


diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index f9b109bfc6a6..11d3103890dc 100644
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -277,6 +277,13 @@ The following sysctls are available for the XFS filesystem:
 	references and returns timed-out AGs back to the free stream
 	pool.
 
+  fs.xfs.inode_gc_delay_ms
+	(Units: milliseconds   Min: 0  Default: 2000  Max: 3600000)
+	The amount of time to delay cleanup work that happens after a file is
+	closed by all programs.  This involves clearing speculative
+	preallocations from linked files and freeing unlinked files.  A higher
+	value here increases batching at a risk of background work storms.
+
   fs.xfs.speculative_prealloc_lifetime
 	(Units: seconds   Min: 1  Default: 300  Max: 86400)
 	The interval at which the background scanning for inodes
diff --git a/fs/xfs/xfs_globals.c b/fs/xfs/xfs_globals.c
index f62fa652c2fd..e81f3a39bebc 100644
--- a/fs/xfs/xfs_globals.c
+++ b/fs/xfs/xfs_globals.c
@@ -28,6 +28,11 @@ xfs_param_t xfs_params = {
 	.rotorstep	= {	1,		1,		255	},
 	.inherit_nodfrg	= {	0,		1,		1	},
 	.fstrm_timer	= {	1,		30*100,		3600*100},
+
+	/* Values below here are measured in milliseconds */
+	.inodegc_ms	= {	0,		5000,		3600*1000},
+
+	/* Values below here are measured in seconds */
 	.blockgc_timer	= {	1,		300,		3600*24},
 };
 
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index e0803544ea19..69f7fb048116 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -221,8 +221,12 @@ xfs_gc_delay_ms(
 	struct xfs_mount	*mp,
 	unsigned int		tag)
 {
+	unsigned int		default_ms;
+
 	switch (tag) {
 	case XFS_ICI_INODEGC_TAG:
+		default_ms = xfs_inodegc_ms;
+
 		/* If we're in a shrinker, kick off the worker immediately. */
 		if (current->reclaim_state != NULL) {
 			trace_xfs_inodegc_delay_mempressure(mp,
@@ -235,7 +239,7 @@ xfs_gc_delay_ms(
 		return 0;
 	}
 
-	return 0;
+	return default_ms;
 }
 
 /*
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index c174262a074e..89bafcce3579 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -99,6 +99,7 @@ typedef __u32			xfs_nlink_t;
 #define xfs_inherit_nodefrag	xfs_params.inherit_nodfrg.val
 #define xfs_fstrm_centisecs	xfs_params.fstrm_timer.val
 #define xfs_blockgc_secs	xfs_params.blockgc_timer.val
+#define xfs_inodegc_ms		xfs_params.inodegc_ms.val
 
 #define current_cpu()		(raw_smp_processor_id())
 #define current_set_flags_nested(sp, f)		\
diff --git a/fs/xfs/xfs_sysctl.c b/fs/xfs/xfs_sysctl.c
index 546a6cd96729..6495887f4f00 100644
--- a/fs/xfs/xfs_sysctl.c
+++ b/fs/xfs/xfs_sysctl.c
@@ -176,6 +176,15 @@ static struct ctl_table xfs_table[] = {
 		.extra1		= &xfs_params.fstrm_timer.min,
 		.extra2		= &xfs_params.fstrm_timer.max,
 	},
+	{
+		.procname	= "inode_gc_delay_ms",
+		.data		= &xfs_params.inodegc_ms.val,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &xfs_params.inodegc_ms.min,
+		.extra2		= &xfs_params.inodegc_ms.max
+	},
 	{
 		.procname	= "speculative_prealloc_lifetime",
 		.data		= &xfs_params.blockgc_timer.val,
diff --git a/fs/xfs/xfs_sysctl.h b/fs/xfs/xfs_sysctl.h
index 7692e76ead33..9a867b379a1f 100644
--- a/fs/xfs/xfs_sysctl.h
+++ b/fs/xfs/xfs_sysctl.h
@@ -36,6 +36,7 @@ typedef struct xfs_param {
 	xfs_sysctl_val_t inherit_nodfrg;/* Inherit the "nodefrag" inode flag. */
 	xfs_sysctl_val_t fstrm_timer;	/* Filestream dir-AG assoc'n timeout. */
 	xfs_sysctl_val_t blockgc_timer;	/* Interval between blockgc scans */
+	xfs_sysctl_val_t inodegc_ms;	/* Inode inactivation scan interval */
 } xfs_param_t;
 
 /*