slub: extend slub debug to handle multiple slabs

Extend the slub_debug syntax to "slub_debug=<flags>[,<slub>]*", where
<slub> may contain an asterisk at the end.  For example, the following
would poison all kmalloc slabs:

	slub_debug=P,kmalloc*

and the following would apply the default flags to all kmalloc and all
block IO slabs:

	slub_debug=,bio*,kmalloc*

Please note that a similar patch was posted by Iliyan Malchev some time
ago but was never merged:

	https://marc.info/?l=linux-mm&m=131283905330474&w=2

Link: http://lkml.kernel.org/r/20180928111139.27962-1-atomlin@redhat.com
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Iliyan Malchev <malchev@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
index 3a775fd..1959288 100644 (file)
--- a/Documentation/vm/slub.rst
+++ b/Documentation/vm/slub.rst
@@ -36,9 +36,10 @@ debugging is enabled. Format:
 
 slub_debug=<Debug-Options>
        Enable options for all slabs
-slub_debug=<Debug-Options>,<slab name>
-       Enable options only for select slabs
 
+slub_debug=<Debug-Options>,<slab name1>,<slab name2>,...
+       Enable options only for select slabs (no spaces
+       after a comma)
 
 Possible debug options are::
 
@@ -62,7 +63,12 @@ Trying to find an issue in the dentry cache? Try::
 
        slub_debug=,dentry
 
-to only enable debugging on the dentry cache.
+to only enable debugging on the dentry cache.  You may use an asterisk at the
+end of the slab name, in order to cover all slabs with the same prefix.  For
+example, here's how you can poison the dentry cache as well as all kmalloc
+slabs:
+
+       slub_debug=P,kmalloc-*,dentry
 
 Red zoning and tracking may realign the slab.  We can just apply sanity checks
 to the dentry cache with::

diff --git a/mm/slub.c b/mm/slub.c
index 37e82a0..18bd07d 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1276,16 +1276,54 @@ out:
 
 __setup("slub_debug", setup_slub_debug);
 
+/*
+ * kmem_cache_flags - apply debugging options to the cache
+ * @object_size:       the size of an object without meta data
+ * @flags:             flags to set
+ * @name:              name of the cache
+ * @ctor:              constructor function
+ *
+ * Debug option(s) are applied to @flags. In addition to the debug
+ * option(s), if a slab name (or multiple) is specified i.e.
+ * slub_debug=<Debug-Options>,<slab name1>,<slab name2> ...
+ * then only the select slabs will receive the debug option(s).
+ */
 slab_flags_t kmem_cache_flags(unsigned int object_size,
        slab_flags_t flags, const char *name,
        void (*ctor)(void *))
 {
-       /*
-        * Enable debugging if selected on the kernel commandline.
-        */
-       if (slub_debug && (!slub_debug_slabs || (name &&
-               !strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)))))
-               flags |= slub_debug;
+       char *iter;
+       size_t len;
+
+       /* If slub_debug = 0, it folds into the if conditional. */
+       if (!slub_debug_slabs)
+               return flags | slub_debug;
+
+       len = strlen(name);
+       iter = slub_debug_slabs;
+       while (*iter) {
+               char *end, *glob;
+               size_t cmplen;
+
+               end = strchr(iter, ',');
+               if (!end)
+                       end = iter + strlen(iter);
+
+               glob = strnchr(iter, end - iter, '*');
+               if (glob)
+                       cmplen = glob - iter;
+               else
+                       cmplen = max_t(size_t, len, (end - iter));
+
+               if (!strncmp(name, iter, cmplen)) {
+                       flags |= slub_debug;
+                       break;
+               }
+
+               if (!*end)
+                       break;
+               iter = end + 1;
+       }
 
        return flags;
 }