linux-kernel - [RFC PATCH v4 15/15] dcache: Add CONFIG_DCACHE

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Message-Id: <20190430030746.26102-16-tobin@kernel.org>
Date:   Tue, 30 Apr 2019 13:07:46 +1000
From:   "Tobin C. Harding" <tobin@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Tobin C. Harding" <tobin@...nel.org>,
        Roman Gushchin <guro@...com>,
        Alexander Viro <viro@....linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Pekka Enberg <penberg@...helsinki.fi>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Christopher Lameter <cl@...ux.com>,
        Matthew Wilcox <willy@...radead.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Andreas Dilger <adilger@...ger.ca>,
        Waiman Long <longman@...hat.com>,
        Tycho Andersen <tycho@...ho.ws>,
        "Theodore Ts'o" <tytso@....edu>, Andi Kleen <ak@...ux.intel.com>,
        David Chinner <david@...morbit.com>,
        Nick Piggin <npiggin@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jonathan Corbet <corbet@....net>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 15/15] dcache: Add CONFIG_DCACHE_SMO

In an attempt to make the SMO patchset as non-invasive as possible add a
config option CONFIG_DCACHE_SMO (under "Memory Management options") for
enabling SMO for the DCACHE.  Whithout this option dcache constructor is
used but no other code is built in, with this option enabled slab
mobility is enabled and the isolate/migrate functions are built in.

Add CONFIG_DCACHE_SMO to guard the partial shrinking of the dcache via
Slab Movable Objects infrastructure.

Signed-off-by: Tobin C. Harding <tobin@...nel.org>
---
 fs/dcache.c | 4 ++++
 mm/Kconfig  | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/fs/dcache.c b/fs/dcache.c
index 3f9daba1cc78..9edce104613b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3068,6 +3068,7 @@ void d_tmpfile(struct dentry *dentry, struct inode *inode)
 }
 EXPORT_SYMBOL(d_tmpfile);
 
+#ifdef CONFIG_DCACHE_SMO
 /*
  * d_isolate() - Dentry isolation callback function.
  * @s: The dentry cache.
@@ -3140,6 +3141,7 @@ static void d_partial_shrink(struct kmem_cache *s, void **_unused, int __unused,
 
 	kfree(private);
 }
+#endif	/* CONFIG_DCACHE_SMO */
 
 static __initdata unsigned long dhash_entries;
 static int __init set_dhash_entries(char *str)
@@ -3186,7 +3188,9 @@ static void __init dcache_init(void)
 					   sizeof_field(struct dentry, d_iname),
 					   dcache_ctor);
 
+#ifdef CONFIG_DCACHE_SMO
 	kmem_cache_setup_mobility(dentry_cache, d_isolate, d_partial_shrink);
+#endif
 
 	/* Hash may have been set up in dcache_init_early */
 	if (!hashdist)
diff --git a/mm/Kconfig b/mm/Kconfig
index 47040d939f3b..92fc27ad3472 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -265,6 +265,13 @@ config SMO_NODE
        help
          On NUMA systems enable moving objects to and from a specified node.
 
+config DCACHE_SMO
+       bool "Enable Slab Movable Objects for the dcache"
+       depends on SLUB
+       help
+         Under memory pressure we can try to free dentry slab cache objects from
+         the partial slab list if this is enabled.
+
 config PHYS_ADDR_T_64BIT
 	def_bool 64BIT
 
-- 
2.21.0