From 2e5de42445217c7c1310af8f4b3fe6f66bd865b1 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Tue, 21 Jul 2020 09:36:39 -0300 Subject: cifs: reduce number of referral requests in DFS link lookups When looking up the DFS cache with a referral path that has more than two path components, and is a complete prefix of an existing cache entry, do not request another referral and just return the matched entry as specified in MS-DFSC 3.2.5.5 Receiving a Root Referral Request or Link Referral Request. Signed-off-by: Paulo Alcantara (SUSE) Reviewed-by: Aurelien Aptel Signed-off-by: Steve French --- fs/cifs/dfs_cache.c | 79 +++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 68 insertions(+), 11 deletions(-) (limited to 'fs') diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c index df81c718d2fa..dae2f41e4f21 100644 --- a/fs/cifs/dfs_cache.c +++ b/fs/cifs/dfs_cache.c @@ -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; } -- cgit v1.2.3-70-g09d2