[lustre-devel] [PATCH 13/15] lustre: obdclass: fix race in class_del_profile

[James Simmons]

From: Li Dongyang <dongyangli at ddn.com>

Move profile lookup and remove from lustre_profile_list
into the same critical section, otherwise we could race with
class_del_profiles or another class_del_profile.

Do not create duplicate mount opts in the client config,
otherwise we will add duplicate lustre_profile to
lustre_profile_list for a single mount.

WC-bug-id: https://jira.whamcloud.com/browse/LU-15305
Lustre-commit: 83d3f42118579d7fb ("LU-15305 obdclass: fix race in class_del_profile")
Signed-off-by: Li Dongyang <dongyangli at ddn.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48802
Reviewed-by: Andreas Dilger <adilger at whamcloud.com>
Reviewed-by: James Simmons <jsimmons at infradead.org>
Reviewed-by: Oleg Drokin <green at whamcloud.com>
Signed-off-by: James Simmons <jsimmons at infradead.org>
---
 fs/lustre/obdclass/obd_config.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/fs/lustre/obdclass/obd_config.c b/fs/lustre/obdclass/obd_config.c
index 2b24276..75fc6a6 100644
--- a/fs/lustre/obdclass/obd_config.c
+++ b/fs/lustre/obdclass/obd_config.c
@@ -622,21 +622,28 @@ static int class_del_conn(struct obd_device *obd, struct lustre_cfg *lcfg)
 static LIST_HEAD(lustre_profile_list);
 static DEFINE_SPINLOCK(lustre_profile_list_lock);
 
-struct lustre_profile *class_get_profile(const char *prof)
+static struct lustre_profile *class_get_profile_nolock(const char *prof)
 {
 	struct lustre_profile *lprof;
 
-	spin_lock(&lustre_profile_list_lock);
 	list_for_each_entry(lprof, &lustre_profile_list, lp_list) {
-		if (!strcmp(lprof->lp_profile, prof)) {
+		if (strcmp(lprof->lp_profile, prof) == 0) {
 			lprof->lp_refs++;
-			spin_unlock(&lustre_profile_list_lock);
 			return lprof;
 		}
 	}
-	spin_unlock(&lustre_profile_list_lock);
 	return NULL;
 }
+
+struct lustre_profile *class_get_profile(const char *prof)
+{
+	struct lustre_profile *lprof;
+
+	spin_lock(&lustre_profile_list_lock);
+	lprof = class_get_profile_nolock(prof);
+	spin_unlock(&lustre_profile_list_lock);
+	return lprof;
+}
 EXPORT_SYMBOL(class_get_profile);
 
 /** Create a named "profile".
@@ -701,9 +708,9 @@ void class_del_profile(const char *prof)
 
 	CDEBUG(D_CONFIG, "Del profile %s\n", prof);
 
-	lprof = class_get_profile(prof);
+	spin_lock(&lustre_profile_list_lock);
+	lprof = class_get_profile_nolock(prof);
 	if (lprof) {
-		spin_lock(&lustre_profile_list_lock);
 		/* because get profile increments the ref counter */
 		lprof->lp_refs--;
 		list_del(&lprof->lp_list);
@@ -711,6 +718,8 @@ void class_del_profile(const char *prof)
 		spin_unlock(&lustre_profile_list_lock);
 
 		class_put_profile(lprof);
+	} else {
+		spin_unlock(&lustre_profile_list_lock);
 	}
 }
 EXPORT_SYMBOL(class_del_profile);
-- 
1.8.3.1