From: Oleg Drokin <oleg.drokin@intel.com>
Date: Fri, 10 Apr 2015 02:29:20 +0000 (-0400)
Subject: LU-6447 mdt: mdt_identity_upcall to not block with rwlock held
X-Git-Tag: 2.8.57~46
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=e8273a3dd71c4e6ab5ca9de3fbfbc0f7603d6930;hp=7334a2d33cc4cf4cda0c81b126c4cb8ab28a888d

LU-6447 mdt: mdt_identity_upcall to not block with rwlock held

mdt_identity_upcall is currently calling call_usermodehelper
with an rwlock held, which is a no-no since it allocates memory
and schedules. Just replace the rwlock with a rw_semaphore.

Change-Id: I7b063a4db47313fbae6241da7bcec2c397b8e8c4
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-on: http://review.whamcloud.com/14432
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
---

diff --git a/lustre/include/upcall_cache.h b/lustre/include/upcall_cache.h
index 46cfe65..d239a26 100644
--- a/lustre/include/upcall_cache.h
+++ b/lustre/include/upcall_cache.h
@@ -121,7 +121,7 @@ struct upcall_cache_ops {
 struct upcall_cache {
 	struct list_head	uc_hashtable[UC_CACHE_HASH_SIZE];
 	spinlock_t		uc_lock;
-	rwlock_t		uc_upcall_rwlock;
+	struct rw_semaphore	uc_upcall_rwsem;
 
 	char			uc_name[40];		/* for upcall */
 	char			uc_upcall[UC_CACHE_UPCALL_MAXPATH];
diff --git a/lustre/mdt/mdt_identity.c b/lustre/mdt/mdt_identity.c
index 235444c..7d55a0e 100644
--- a/lustre/mdt/mdt_identity.c
+++ b/lustre/mdt/mdt_identity.c
@@ -113,7 +113,7 @@ static int mdt_identity_do_upcall(struct upcall_cache *cache,
         /* There is race condition:
          * "uc_upcall" was changed just after "is_identity_get_disabled" check.
          */
-	read_lock(&cache->uc_upcall_rwlock);
+	down_read(&cache->uc_upcall_rwsem);
         CDEBUG(D_INFO, "The upcall is: '%s'\n", cache->uc_upcall);
 
         if (unlikely(!strcmp(cache->uc_upcall, "NONE"))) {
@@ -141,8 +141,8 @@ static int mdt_identity_do_upcall(struct upcall_cache *cache,
         }
         EXIT;
 out:
-	read_unlock(&cache->uc_upcall_rwlock);
-        return rc;
+	up_read(&cache->uc_upcall_rwsem);
+	return rc;
 }
 
 static int mdt_identity_parse_downcall(struct upcall_cache *cache,
diff --git a/lustre/mdt/mdt_lproc.c b/lustre/mdt/mdt_lproc.c
index 38bc9ab..5141394 100644
--- a/lustre/mdt/mdt_lproc.c
+++ b/lustre/mdt/mdt_lproc.c
@@ -281,9 +281,9 @@ static int mdt_identity_upcall_seq_show(struct seq_file *m, void *data)
 	struct mdt_device *mdt = mdt_dev(obd->obd_lu_dev);
 	struct upcall_cache *hash = mdt->mdt_identity_cache;
 
-	read_lock(&hash->uc_upcall_rwlock);
+	down_read(&hash->uc_upcall_rwsem);
 	seq_printf(m, "%s\n", hash->uc_upcall);
-	read_unlock(&hash->uc_upcall_rwlock);
+	up_read(&hash->uc_upcall_rwsem);
 	return 0;
 }
 
@@ -309,9 +309,9 @@ mdt_identity_upcall_seq_write(struct file *file, const char __user *buffer,
 		GOTO(failed, rc = -EFAULT);
 
 	/* Remove any extraneous bits from the upcall (e.g. linefeeds) */
-	write_lock(&hash->uc_upcall_rwlock);
+	down_write(&hash->uc_upcall_rwsem);
 	sscanf(kernbuf, "%s", hash->uc_upcall);
-	write_unlock(&hash->uc_upcall_rwlock);
+	up_write(&hash->uc_upcall_rwsem);
 
 	if (strcmp(hash->uc_name, mdt_obd_name(mdt)) != 0)
 		CWARN("%s: write to upcall name %s\n",
diff --git a/lustre/obdclass/upcall_cache.c b/lustre/obdclass/upcall_cache.c
index 165e717..0e350ab 100644
--- a/lustre/obdclass/upcall_cache.c
+++ b/lustre/obdclass/upcall_cache.c
@@ -428,7 +428,7 @@ struct upcall_cache *upcall_cache_init(const char *name, const char *upcall,
 		RETURN(ERR_PTR(-ENOMEM));
 
 	spin_lock_init(&cache->uc_lock);
-	rwlock_init(&cache->uc_upcall_rwlock);
+	init_rwsem(&cache->uc_upcall_rwsem);
 	for (i = 0; i < UC_CACHE_HASH_SIZE; i++)
 		INIT_LIST_HEAD(&cache->uc_hashtable[i]);
 	strlcpy(cache->uc_name, name, sizeof(cache->uc_name));