Commit 48d240bf authored by Paulo Alcantara's avatar Paulo Alcantara Committed by Steve French
Browse files

cifs: avoid re-lookups in dfs_cache_find() 



Simply downgrade the write lock on cache updates from
cache_refresh_path() and avoid unnecessary re-lookup in
dfs_cache_find().

Signed-off-by: default avatarPaulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 9fb0db40

fs/cifs/dfs_cache.c

+34 −24
Original line number Diff line number Diff line
@@ -558,7 +558,8 @@ static void remove_oldest_entry_locked(void) 
}



/* Add a new DFS cache entry */

static int add_cache_entry_locked(struct dfs_info3_param *refs, int numrefs)

static struct cache_entry *add_cache_entry_locked(struct dfs_info3_param *refs,

						  int numrefs)

{

	int rc;

	struct cache_entry *ce;
@@ -573,11 +574,11 @@ static int add_cache_entry_locked(struct dfs_info3_param *refs, int numrefs) 


	rc = cache_entry_hash(refs[0].path_name, strlen(refs[0].path_name), &hash);

	if (rc)

		return rc;

		return ERR_PTR(rc);



	ce = alloc_cache_entry(refs, numrefs);

	if (IS_ERR(ce))

		return PTR_ERR(ce);

		return ce;



	spin_lock(&cache_ttl_lock);

	if (!cache_ttl) {
@@ -594,7 +595,7 @@ static int add_cache_entry_locked(struct dfs_info3_param *refs, int numrefs) 


	atomic_inc(&cache_count);



	return 0;

	return ce;

}



/* Check if two DFS paths are equal.  @s1 and @s2 are expected to be in @cache_cp's charset */
@@ -767,8 +768,12 @@ static int get_dfs_referral(const unsigned int xid, struct cifs_ses *ses, const 
 *

 * For interlinks, cifs_mount() and expand_dfs_referral() are supposed to

 * handle them properly.

 *

 * On success, return entry with acquired lock for reading, otherwise error ptr.

 */

static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, const char *path)

static struct cache_entry *cache_refresh_path(const unsigned int xid,

					      struct cifs_ses *ses,

					      const char *path)

{

	struct dfs_info3_param *refs = NULL;

	struct cache_entry *ce;
@@ -780,10 +785,9 @@ static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, cons 
	down_read(&htable_rw_lock);



	ce = lookup_cache_entry(path);

	if (!IS_ERR(ce) && !cache_entry_expired(ce)) {

		up_read(&htable_rw_lock);

		return 0;

	}

	if (!IS_ERR(ce) && !cache_entry_expired(ce))

		return ce;



	/*

	 * Unlock shared access as we don't want to hold any locks while getting

	 * a new referral.  The @ses used for performing the I/O could be
@@ -797,8 +801,10 @@ static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, cons 
	 * Request a new DFS referral in order to create or update a cache entry.

	 */

	rc = get_dfs_referral(xid, ses, path, &refs, &numrefs);

	if (rc)

	if (rc) {

		ce = ERR_PTR(rc);

		goto out;

	}



	dump_refs(refs, numrefs);
@@ -806,16 +812,24 @@ static int cache_refresh_path(const unsigned int xid, struct cifs_ses *ses, cons 
	/* Re-check as another task might have it added or refreshed already */

	ce = lookup_cache_entry(path);

	if (!IS_ERR(ce)) {

		if (cache_entry_expired(ce))

		if (cache_entry_expired(ce)) {

			rc = update_cache_entry_locked(ce, refs, numrefs);

			if (rc)

				ce = ERR_PTR(rc);

		}

	} else {

		rc = add_cache_entry_locked(refs, numrefs);

		ce = add_cache_entry_locked(refs, numrefs);

	}



	if (IS_ERR(ce)) {

		up_write(&htable_rw_lock);

		goto out;

	}



	downgrade_write(&htable_rw_lock);

out:

	free_dfs_info_array(refs, numrefs);

	return rc;

	return ce;

}



/*
@@ -935,15 +949,8 @@ int dfs_cache_find(const unsigned int xid, struct cifs_ses *ses, const struct nl 
	if (IS_ERR(npath))

		return PTR_ERR(npath);



	rc = cache_refresh_path(xid, ses, npath);

	if (rc)

		goto out_free_path;



	down_read(&htable_rw_lock);



	ce = lookup_cache_entry(npath);

	ce = cache_refresh_path(xid, ses, npath);

	if (IS_ERR(ce)) {

		up_read(&htable_rw_lock);

		rc = PTR_ERR(ce);

		goto out_free_path;

	}
@@ -1039,10 +1046,13 @@ int dfs_cache_update_tgthint(const unsigned int xid, struct cifs_ses *ses, 


	cifs_dbg(FYI, "%s: update target hint - path: %s\n", __func__, npath);



	rc = cache_refresh_path(xid, ses, npath);

	if (rc)

	ce = cache_refresh_path(xid, ses, npath);

	if (IS_ERR(ce)) {

		rc = PTR_ERR(ce);

		goto out_free_path;

	}



	up_read(&htable_rw_lock);

	down_write(&htable_rw_lock);



	ce = lookup_cache_entry(npath);