[PATCH] slub: extend slub debug to handle multiple slabs

[Aaron Tomlin]

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


Signed-off-by: Aaron Tomlin <atom...@redhat.com>
---
 Documentation/vm/slub.rst | 12 +++++++++---
 mm/slub.c                 | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
index 3a775fd64e2d..195928808bac 100644
--- 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 8da34a8af53d..27281867cbe0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1283,9 +1283,37 @@ slab_flags_t kmem_cache_flags(unsigned int object_size,
        /*
         * 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 *end, *n, *glob;
+       int len = strlen(name);
+
+       /* If slub_debug = 0, it folds into the if conditional. */
+       if (!slub_debug_slabs)
+               return flags | slub_debug;
+
+       n = slub_debug_slabs;
+       while (*n) {
+               int cmplen;
+
+               end = strchr(n, ',');
+               if (!end)
+                       end = n + strlen(n);
+
+               glob = strnchr(n, end - n, '*');
+               if (glob)
+                       cmplen = glob - n;
+               else
+                       cmplen = max(len, end - n);
+
+               if (!strncmp(name, n, cmplen)) {
+                       flags |= slub_debug;
+                       break;
+               }
+
+               if (!*end)
+                       break;
+               n = end + 1;
+       }
 
        return flags;
 }
-- 
2.14.4