cifs: reduce number of referral requests in DFS link lookups (2e5de424) · Commits · 戴 / test

fs/cifs/dfs_cache.c

+68 −11

Original line number	Diff line number	Diff line
		@@ -490,16 +490,7 @@ static int add_cache_entry(const char *path, unsigned int hash,
		return 0;
		}

		/*
		* Find a DFS cache entry in hash table and optionally check prefix path against
		* @path.
		* Use whole path components in the match.
		* Must be called with htable_rw_lock held.
		*
		* Return ERR_PTR(-ENOENT) if the entry is not found.
		*/
		static struct cache_entry lookup_cache_entry(const char path,
		unsigned int *hash)
		static struct cache_entry __lookup_cache_entry(const char path)
		{
		struct cache_entry *ce;
		unsigned int h;
		@@ -517,9 +508,75 @@ static struct cache_entry lookup_cache_entry(const char path,

		if (!found)
		ce = ERR_PTR(-ENOENT);
		return ce;
		}

		/*
		* Find a DFS cache entry in hash table and optionally check prefix path against
		* @path.
		* Use whole path components in the match.
		* Must be called with htable_rw_lock held.
		*
		* Return ERR_PTR(-ENOENT) if the entry is not found.
		*/
		static struct cache_entry lookup_cache_entry(const char path, unsigned int *hash)
		{
		struct cache_entry *ce = ERR_PTR(-ENOENT);
		unsigned int h;
		int cnt = 0;
		char *npath;
		char s, e;
		char sep;

		npath = kstrndup(path, strlen(path), GFP_KERNEL);
		if (!npath)
		return ERR_PTR(-ENOMEM);

		s = npath;
		sep = *npath;
		while ((s = strchr(s, sep)) && ++cnt < 3)
		s++;

		if (cnt < 3) {
		h = cache_entry_hash(path, strlen(path));
		ce = __lookup_cache_entry(path);
		goto out;
		}
		/*
		* Handle paths that have more than two path components and are a complete prefix of the DFS
		* referral request path (@path).
		*
		* See MS-DFSC 3.2.5.5 "Receiving a Root Referral Request or Link Referral Request".
		*/
		h = cache_entry_hash(npath, strlen(npath));
		e = npath + strlen(npath) - 1;
		while (e > s) {
		char tmp;

		/* skip separators */
		while (e > s && *e == sep)
		e--;
		if (e == s)
		goto out;

		tmp = *(e+1);
		*(e+1) = 0;

		ce = __lookup_cache_entry(npath);
		if (!IS_ERR(ce)) {
		h = cache_entry_hash(npath, strlen(npath));
		break;
		}

		*(e+1) = tmp;
		/* backward until separator */
		while (e > s && *e != sep)
		e--;
		}
		out:
		if (hash)
		*hash = h;

		kfree(npath);
		return ce;
		}

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