On 7/19/2021 11:51 AM, David Rientjes wrote:

On Tue, 13 Jul 2021, vjitta@codeaurora.org wrote:

quoted

From: Vijayanand Jitta <redacted>

Consider the scenario where CONFIG_SLUB_DEBUG_ON is set
and we would want to disable slub_debug for few slabs.
Using boot parameter with slub_debug=-,slab_name syntax
doesn't work as expected i.e; only disabling debugging for
the specified list of slabs, instead it disables debugging
for all slabs. Fix this.

Signed-off-by: Vijayanand Jitta <redacted>
---
 mm/slub.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index dc863c1..5a88418 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -1429,6 +1429,7 @@ static int __init setup_slub_debug(char *str)
 	char *slab_list;
 	bool global_slub_debug_changed = false;
 	bool slab_list_specified = false;
+	bool slab_list_debug_disable = true;
 
 	slub_debug = DEBUG_DEFAULT_FLAGS;
 	if (*str++ != '=' || !*str)

@@ -1436,7 +1437,6 @@ static int __init setup_slub_debug(char *str)
 		 * No options specified. Switch on full debugging.
 		 */
 		goto out;
-
 	saved_str = str;
 	while (str) {
 		str = parse_slub_debug_flags(str, &flags, &slab_list, true);

@@ -1445,6 +1445,8 @@ static int __init setup_slub_debug(char *str)
 			slub_debug = flags;
 			global_slub_debug_changed = true;
 		} else {
+			if (flags || !IS_ENABLED(CONFIG_SLUB_DEBUG_ON))

Could you explain the check for CONFIG_SLUB_DEBUG_ON here?

Thanks for the review.

The check for CONFIG_SLUB_DEBUG_ON is for below scenario:

Consider CONFIG_SLUB_DEBUG_ON is not set and the below boot parameter is
set incorrectly "slub_debug=-,slab_name", Now without the additional
CONFIG_SLUB_DEBUG_ON check slab_list_debug_disable will still be true
and slub_debug will be set to DEBUG_DEFAULT_FLAGS instead of 0 as the
below check fails.

if (!global_slub_debug_changed && !slab_list_debug_disable)
	slub_debug = 0;

I don't believe that using `-' for slub_debug is *only* useful when 
CONFIG_SLUB_DEBUG_ON is enabled.

'-' is still useful in CONFIG_SLUB_DEBUG_ON disabled case even with the
above check, all the possible cases using '-' work as expected.

i.e;
slub_debug=-.slab_name
slub_debug=flag,slab_name;-,slab_name

Thanks,
Vijay

quoted

+				slab_list_debug_disable = false;
 			slab_list_specified = true;
 		}
 	}

@@ -1456,7 +1458,7 @@ static int __init setup_slub_debug(char *str)
 	 * long as there is no option specifying flags without a slab list.
 	 */
 	if (slab_list_specified) {
-		if (!global_slub_debug_changed)
+		if (!global_slub_debug_changed && !slab_list_debug_disable)
 			slub_debug = 0;
 		slub_debug_string = saved_str;
 	}

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