Commit 11c8b3f8 authored by Paulo Alcantara's avatar Paulo Alcantara Committed by Steve French
Browse files

cifs: don't take exclusive lock for updating target hints 



Avoid contention while updating dfs target hints.  This should be
perfectly fine to update them under shared locks.

Signed-off-by: default avatarPaulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 48d240bf

fs/cifs/dfs_cache.c

+20 −27
Original line number Diff line number Diff line
@@ -269,7 +269,7 @@ static int dfscache_proc_show(struct seq_file *m, void *v) 
			list_for_each_entry(t, &ce->tlist, list) {

				seq_printf(m, "  %s%s\n",

					   t->name,

					   ce->tgthint == t ? " (target hint)" : "");

					   READ_ONCE(ce->tgthint) == t ? " (target hint)" : "");

			}

		}

	}
@@ -321,7 +321,7 @@ static inline void dump_tgts(const struct cache_entry *ce) 
	cifs_dbg(FYI, "target list:\n");

	list_for_each_entry(t, &ce->tlist, list) {

		cifs_dbg(FYI, "  %s%s\n", t->name,

			 ce->tgthint == t ? " (target hint)" : "");

			 READ_ONCE(ce->tgthint) == t ? " (target hint)" : "");

	}

}
@@ -427,7 +427,7 @@ static int cache_entry_hash(const void *data, int size, unsigned int *hash) 
/* Return target hint of a DFS cache entry */

static inline char *get_tgt_name(const struct cache_entry *ce)

{

	struct cache_dfs_tgt *t = ce->tgthint;

	struct cache_dfs_tgt *t = READ_ONCE(ce->tgthint);



	return t ? t->name : ERR_PTR(-ENOENT);

}
@@ -470,6 +470,7 @@ static struct cache_dfs_tgt *alloc_target(const char *name, int path_consumed) 
static int copy_ref_data(const struct dfs_info3_param *refs, int numrefs,

			 struct cache_entry *ce, const char *tgthint)

{

	struct cache_dfs_tgt *target;

	int i;



	ce->ttl = max_t(int, refs[0].ttl, CACHE_MIN_TTL);
@@ -496,8 +497,9 @@ static int copy_ref_data(const struct dfs_info3_param *refs, int numrefs, 
		ce->numtgts++;

	}



	ce->tgthint = list_first_entry_or_null(&ce->tlist,

					       struct cache_dfs_tgt, list);

	target = list_first_entry_or_null(&ce->tlist, struct cache_dfs_tgt,

					  list);

	WRITE_ONCE(ce->tgthint, target);



	return 0;

}
@@ -712,14 +714,15 @@ void dfs_cache_destroy(void) 
static int update_cache_entry_locked(struct cache_entry *ce, const struct dfs_info3_param *refs,

				     int numrefs)

{

	struct cache_dfs_tgt *target;

	char *th = NULL;

	int rc;

	char *s, *th = NULL;



	WARN_ON(!rwsem_is_locked(&htable_rw_lock));



	if (ce->tgthint) {

		s = ce->tgthint->name;

		th = kstrdup(s, GFP_ATOMIC);

	target = READ_ONCE(ce->tgthint);

	if (target) {

		th = kstrdup(target->name, GFP_ATOMIC);

		if (!th)

			return -ENOMEM;

	}
@@ -896,7 +899,7 @@ static int get_targets(struct cache_entry *ce, struct dfs_cache_tgt_list *tl) 
		}

		it->it_path_consumed = t->path_consumed;



		if (ce->tgthint == t)

		if (READ_ONCE(ce->tgthint) == t)

			list_add(&it->it_list, head);

		else

			list_add_tail(&it->it_list, head);
@@ -1052,23 +1055,14 @@ int dfs_cache_update_tgthint(const unsigned int xid, struct cifs_ses *ses, 
		goto out_free_path;

	}



	up_read(&htable_rw_lock);

	down_write(&htable_rw_lock);



	ce = lookup_cache_entry(npath);

	if (IS_ERR(ce)) {

		rc = PTR_ERR(ce);

		goto out_unlock;

	}



	t = ce->tgthint;

	t = READ_ONCE(ce->tgthint);



	if (likely(!strcasecmp(it->it_name, t->name)))

		goto out_unlock;



	list_for_each_entry(t, &ce->tlist, list) {

		if (!strcasecmp(t->name, it->it_name)) {

			ce->tgthint = t;

			WRITE_ONCE(ce->tgthint, t);

			cifs_dbg(FYI, "%s: new target hint: %s\n", __func__,

				 it->it_name);

			break;
@@ -1076,7 +1070,7 @@ int dfs_cache_update_tgthint(const unsigned int xid, struct cifs_ses *ses, 
	}



out_unlock:

	up_write(&htable_rw_lock);

	up_read(&htable_rw_lock);

out_free_path:

	kfree(npath);

	return rc;
@@ -1106,21 +1100,20 @@ void dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt 


	cifs_dbg(FYI, "%s: path: %s\n", __func__, path);



	if (!down_write_trylock(&htable_rw_lock))

		return;

	down_read(&htable_rw_lock);



	ce = lookup_cache_entry(path);

	if (IS_ERR(ce))

		goto out_unlock;



	t = ce->tgthint;

	t = READ_ONCE(ce->tgthint);



	if (unlikely(!strcasecmp(it->it_name, t->name)))

		goto out_unlock;



	list_for_each_entry(t, &ce->tlist, list) {

		if (!strcasecmp(t->name, it->it_name)) {

			ce->tgthint = t;

			WRITE_ONCE(ce->tgthint, t);

			cifs_dbg(FYI, "%s: new target hint: %s\n", __func__,

				 it->it_name);

			break;
@@ -1128,7 +1121,7 @@ void dfs_cache_noreq_update_tgthint(const char *path, const struct dfs_cache_tgt 
	}



out_unlock:

	up_write(&htable_rw_lock);

	up_read(&htable_rw_lock);

}



/**