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authorPaulo Alcantara <pc@cjr.nz>2020-07-21 15:36:39 +0300
committerSteve French <stfrench@microsoft.com>2020-08-03 02:00:26 +0300
commit2e5de42445217c7c1310af8f4b3fe6f66bd865b1 (patch)
treec28c20794e0d9840bd004ec1f43fd318a5c9b84c /fs/cifs
parent565674d613d7f45d87284ba9f0be730ce4b335d0 (diff)
downloadlinux-2e5de42445217c7c1310af8f4b3fe6f66bd865b1.tar.xz
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) <pc@cjr.nz> Reviewed-by: Aurelien Aptel <aaptel@suse.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs')
-rw-r--r--fs/cifs/dfs_cache.c79
1 files changed, 68 insertions, 11 deletions
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;
}