[2/2] cifs: Invoke id mapping functions (try #15)

Commit Message

Shirish Pargaonkar April 14, 2011, 3:16 a.m. UTC

From: Shirish Pargaonkar <[e-mail]>

rb tree search and insertion routines.

A SID which needs to be mapped, is looked up in one of the rb trees
depending whether SID is either owner or group SID.
If found in the tree, a (mapped) id from that node is assigned to
uid or gid as appropriate.  If unmapped, an upcall is attempted to
map the SID to an id.  If upcall is successful, node is marked as
mapped.  If upcall fails, node stays marked as unmapped and a mapping
is attempted again only after an arbitrary time period has passed.

To map a SID, which can be either a Owner SID or a Group SID, key
description starts with the string "os" or "gs" followed by SID converted
to a string. Without "os" or "gs", cifs.upcall does not know whether
SID needs to be mapped to either an uid or a gid.

Nodes in rb tree have fields to prevent multiple upcalls for
a SID.  Adding and removing nodes is done within global locks.
shrinker routine does not prune a node if mapping for that node
is either pending or or node was recently created (before timeout
period expires and node could be purged). The timeout period should
be long enough at least for an upcall to return back to cifs.
Every time an existing node is accessed, its timestamp is updated
to prevent it from getting erased.

For now, cifs.upcall is only used to map a SID to an id (uid or gid) but
it would be used to obtain an SID (string) for an id.


Signed-off-by: Shirish Pargaonkar <[e-mail]>
---
 fs/cifs/cifsacl.c |  308 ++++++++++++++++++++++++++++++++++++++++++++++++----
 fs/cifs/cifsacl.h |   24 ++++
 2 files changed, 308 insertions(+), 24 deletions(-)

Patch

diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index cad8d9b..609f291 100644
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -54,7 +54,30 @@  static const struct cifs_sid sid_authusers = {
 /* group users */
 static const struct cifs_sid sid_user = {1, 2 , {0, 0, 0, 0, 0, 5}, {} };
 
-static const struct cred *root_cred;
+const struct cred *root_cred;
+
+static void
+shrink_idmap_tree(struct rb_root *root, int nr_to_scan, int *nr_rem,
+			int *nr_del)
+{
+	struct rb_node *node;
+	struct rb_node *tmp;
+	struct cifs_sid_id *psidid;
+
+	node = rb_first(root);
+	while (node) {
+		tmp = node;
+		node = rb_next(tmp);
+		psidid = rb_entry(tmp, struct cifs_sid_id, rbnode);
+		if (time_after(psidid->time + SID_MAP_EXPIRE, jiffies) ||
+				(nr_to_scan == 0) || (*nr_del == nr_to_scan))
+			++(*nr_rem);
+		else {
+			rb_erase(tmp, root);
+			++(*nr_del);
+		}
+	}
+}
 
 /*
  * Run idmap cache shrinker.
@@ -62,9 +85,21 @@  static const struct cred *root_cred;
 static int
 cifs_idmap_shrinker(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
 {
-	/* Use a pruning scheme in a subsequent patch instead */
-	cifs_destroy_idmaptrees();
-	return 0;
+	int nr_del = 0;
+	int nr_rem = 0;
+	struct rb_root *root;
+
+	root = &uidtree;
+	spin_lock(&siduidlock);
+	shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
+	spin_unlock(&siduidlock);
+
+	root = &gidtree;
+	spin_lock(&sidgidlock);
+	shrink_idmap_tree(root, nr_to_scan, &nr_rem, &nr_del);
+	spin_unlock(&sidgidlock);
+
+	return nr_rem;
 }
 
 static struct shrinker cifs_shrinker = {
@@ -92,7 +127,6 @@  cifs_idmap_key_destroy(struct key *key)
 	kfree(key->payload.data);
 }
 
-static
 struct key_type cifs_idmap_key_type = {
 	.name        = "cifs.cifs_idmap",
 	.instantiate = cifs_idmap_key_instantiate,
@@ -101,6 +135,206 @@  struct key_type cifs_idmap_key_type = {
 	.match       = user_match,
 };
 
+static void
+sid_to_str(struct cifs_sid *sidptr, char *sidstr)
+{
+	int i;
+	unsigned long saval;
+	char *strptr;
+
+	strptr = sidstr;
+
+	sprintf(strptr, "%s", "S");
+	strptr = sidstr + strlen(sidstr);
+
+	sprintf(strptr, "-%d", sidptr->revision);
+	strptr = sidstr + strlen(sidstr);
+
+	for (i = 0; i < 6; ++i) {
+		if (sidptr->authority[i]) {
+			sprintf(strptr, "-%d", sidptr->authority[i]);
+			strptr = sidstr + strlen(sidstr);
+		}
+	}
+
+	for (i = 0; i < sidptr->num_subauth; ++i) {
+		saval = le32_to_cpu(sidptr->sub_auth[i]);
+		sprintf(strptr, "-%ld", saval);
+		strptr = sidstr + strlen(sidstr);
+	}
+}
+
+static void
+id_rb_insert(struct rb_root *root, struct cifs_sid *sidptr,
+		struct cifs_sid_id **psidid, char *typestr)
+{
+	int rc;
+	char *strptr;
+	struct rb_node *node = root->rb_node;
+	struct rb_node *parent = NULL;
+	struct rb_node **linkto = &(root->rb_node);
+	struct cifs_sid_id *lsidid;
+
+	while (node) {
+		lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
+		parent = node;
+		rc = compare_sids(sidptr, &((lsidid)->sid));
+		if (rc > 0) {
+			linkto = &(node->rb_left);
+			node = node->rb_left;
+		} else if (rc < 0) {
+			linkto = &(node->rb_right);
+			node = node->rb_right;
+		}
+	}
+
+	memcpy(&(*psidid)->sid, sidptr, sizeof(struct cifs_sid));
+	(*psidid)->time = jiffies;
+	(*psidid)->retry = jiffies - (SID_MAP_RETRY + 1);
+
+	sprintf((*psidid)->sidstr, "%s", typestr);
+	strptr = (*psidid)->sidstr + strlen((*psidid)->sidstr);
+	sid_to_str(&(*psidid)->sid, strptr);
+
+	clear_bit(SID_ID_PENDING, &(*psidid)->state);
+	clear_bit(SID_ID_MAPPED, &(*psidid)->state);
+
+	rb_link_node(&(*psidid)->rbnode, parent, linkto);
+	rb_insert_color(&(*psidid)->rbnode, root);
+}
+
+static struct cifs_sid_id *
+id_rb_search(struct rb_root *root, struct cifs_sid *sidptr)
+{
+	int rc;
+	struct rb_node *node = root->rb_node;
+	struct rb_node *parent = NULL;
+	struct rb_node **linkto = &(root->rb_node);
+	struct cifs_sid_id *lsidid;
+
+	while (node) {
+		lsidid = rb_entry(node, struct cifs_sid_id, rbnode);
+		parent = node;
+		rc = compare_sids(sidptr, &((lsidid)->sid));
+		if (rc > 0) {
+			linkto = &(node->rb_left);
+			node = node->rb_left;
+		} else if (rc < 0) {
+			linkto = &(node->rb_right);
+			node = node->rb_right;
+		} else /* node found */
+			return lsidid;
+	}
+
+	return NULL;
+}
+
+static int
+sidid_pending_wait(void *unused)
+{
+	schedule();
+	return signal_pending(current) ? -ERESTARTSYS : 0;
+}
+
+static int
+sid_to_id(struct cifs_sb_info *cifs_sb, struct cifs_sid *psid,
+		struct cifs_fattr *fattr, uint sidtype)
+{
+	int rc;
+	unsigned long cid;
+	struct key *idkey;
+	const struct cred *saved_cred;
+	struct cifs_sid_id *psidid, *npsidid;
+	struct rb_root *cidtree;
+	spinlock_t *cidlock;
+
+	if (sidtype == SIDOWNER) {
+		cid = cifs_sb->mnt_uid; /* default uid, in case upcall fails */
+		cidlock = &siduidlock;
+		cidtree = &uidtree;
+	} else if (sidtype == SIDGROUP) {
+		cid = cifs_sb->mnt_gid; /* default gid, in case upcall fails */
+		cidlock = &sidgidlock;
+		cidtree = &gidtree;
+	} else
+		return -ENOENT;
+
+	spin_lock(cidlock);
+	psidid = id_rb_search(cidtree, psid);
+
+	if (!psidid) { /* node does not exist, allocate one & attempt adding */
+		spin_unlock(cidlock);
+		npsidid = kzalloc(sizeof(struct cifs_sid_id), GFP_KERNEL);
+		if (!npsidid)
+			return -ENOMEM;
+
+		npsidid->sidstr = kmalloc(SIDLEN, GFP_KERNEL);
+		if (!npsidid->sidstr) {
+			kfree(npsidid);
+			return -ENOMEM;
+		}
+
+		spin_lock(cidlock);
+		psidid = id_rb_search(cidtree, psid);
+		if (psidid) { /* node happened to get inserted meanwhile */
+			psidid->time = jiffies; /* update ts for accessing */
+			spin_unlock(cidlock);
+			kfree(npsidid->sidstr);
+			kfree(npsidid);
+		} else {
+			psidid = npsidid;
+			id_rb_insert(cidtree, psid, &psidid,
+					sidtype == SIDOWNER ? "os:" : "gs:");
+			spin_unlock(cidlock);
+		}
+	} else {
+		psidid->time = jiffies; /* update ts for accessing */
+		spin_unlock(cidlock);
+	}
+
+	if (test_bit(SID_ID_MAPPED, &psidid->state)) {
+		cid = psidid->id;
+		goto sid_to_id_out; /* SID mapped */
+	}
+	if (time_after(psidid->retry + SID_MAP_RETRY, jiffies))
+		goto sid_to_id_out; /* wait before re-attempting SID mapping */
+	if (!test_and_set_bit(SID_ID_PENDING, &psidid->state)) {
+		saved_cred = override_creds(root_cred);
+		idkey = request_key(&cifs_idmap_key_type, psidid->sidstr, "");
+		if (IS_ERR(idkey)) {
+			psidid->retry = jiffies;
+			cFYI(1, "%s: Can't map SID to an id", __func__);
+		} else {
+			cid = *(unsigned long *)idkey->payload.value;
+			psidid->id = cid;
+			set_bit(SID_ID_MAPPED, &psidid->state);
+			key_put(idkey);
+			kfree(psidid->sidstr);
+		}
+		revert_creds(saved_cred);
+		clear_bit(SID_ID_PENDING, &psidid->state);
+		wake_up_bit(&psidid->state, SID_ID_PENDING);
+	} else {
+		rc = wait_on_bit(&psidid->state, SID_ID_PENDING,
+				sidid_pending_wait, TASK_INTERRUPTIBLE);
+		if (rc) {
+			cFYI(1, "%s: sidid_pending_wait interrupted %d",
+					__func__, rc);
+			return rc;
+		}
+		if (test_bit(SID_ID_MAPPED, &psidid->state))
+			cid = psidid->id;
+	}
+
+sid_to_id_out:
+	if (sidtype == SIDOWNER)
+		fattr->cf_uid = cid;
+	else
+		fattr->cf_gid = cid;
+
+	return 0;
+}
+
 int
 init_cifs_idmap(void)
 {
@@ -242,16 +476,24 @@  int compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
 	int num_subauth, num_sat, num_saw;
 
 	if ((!ctsid) || (!cwsid))
-		return 0;
+		return 1;
 
 	/* compare the revision */
-	if (ctsid->revision != cwsid->revision)
-		return 0;
+	if (ctsid->revision != cwsid->revision) {
+		if (ctsid->revision > cwsid->revision)
+			return 1;
+		else
+			return -1;
+	}
 
 	/* compare all of the six auth values */
 	for (i = 0; i < 6; ++i) {
-		if (ctsid->authority[i] != cwsid->authority[i])
-			return 0;
+		if (ctsid->authority[i] != cwsid->authority[i]) {
+			if (ctsid->authority[i] > cwsid->authority[i])
+				return 1;
+			else
+				return -1;
+		}
 	}
 
 	/* compare all of the subauth values if any */
@@ -260,12 +502,16 @@  int compare_sids(const struct cifs_sid *ctsid, const struct cifs_sid *cwsid)
 	num_subauth = num_sat < num_saw ? num_sat : num_saw;
 	if (num_subauth) {
 		for (i = 0; i < num_subauth; ++i) {
-			if (ctsid->sub_auth[i] != cwsid->sub_auth[i])
-				return 0;
+			if (ctsid->sub_auth[i] != cwsid->sub_auth[i]) {
+				if (ctsid->sub_auth[i] > cwsid->sub_auth[i])
+					return 1;
+				else
+					return -1;
+			}
 		}
 	}
 
-	return 1; /* sids compare/match */
+	return 0; /* sids compare/match */
 }
 
 
@@ -520,22 +766,22 @@  static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl,
 #ifdef CONFIG_CIFS_DEBUG2
 			dump_ace(ppace[i], end_of_acl);
 #endif
-			if (compare_sids(&(ppace[i]->sid), pownersid))
+			if (compare_sids(&(ppace[i]->sid), pownersid) == 0)
 				access_flags_to_mode(ppace[i]->access_req,
 						     ppace[i]->type,
 						     &fattr->cf_mode,
 						     &user_mask);
-			if (compare_sids(&(ppace[i]->sid), pgrpsid))
+			if (compare_sids(&(ppace[i]->sid), pgrpsid) == 0)
 				access_flags_to_mode(ppace[i]->access_req,
 						     ppace[i]->type,
 						     &fattr->cf_mode,
 						     &group_mask);
-			if (compare_sids(&(ppace[i]->sid), &sid_everyone))
+			if (compare_sids(&(ppace[i]->sid), &sid_everyone) == 0)
 				access_flags_to_mode(ppace[i]->access_req,
 						     ppace[i]->type,
 						     &fattr->cf_mode,
 						     &other_mask);
-			if (compare_sids(&(ppace[i]->sid), &sid_authusers))
+			if (compare_sids(&(ppace[i]->sid), &sid_authusers) == 0)
 				access_flags_to_mode(ppace[i]->access_req,
 						     ppace[i]->type,
 						     &fattr->cf_mode,
@@ -613,10 +859,10 @@  static int parse_sid(struct cifs_sid *psid, char *end_of_acl)
 
 
 /* Convert CIFS ACL to POSIX form */
-static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
-			  struct cifs_fattr *fattr)
+static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
+		struct cifs_ntsd *pntsd, int acl_len, struct cifs_fattr *fattr)
 {
-	int rc;
+	int rc = 0;
 	struct cifs_sid *owner_sid_ptr, *group_sid_ptr;
 	struct cifs_acl *dacl_ptr; /* no need for SACL ptr */
 	char *end_of_acl = ((char *)pntsd) + acl_len;
@@ -638,12 +884,26 @@  static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
 		 le32_to_cpu(pntsd->sacloffset), dacloffset);
 /*	cifs_dump_mem("owner_sid: ", owner_sid_ptr, 64); */
 	rc = parse_sid(owner_sid_ptr, end_of_acl);
-	if (rc)
+	if (rc) {
+		cFYI(1, "%s: Error %d parsing Owner SID", __func__, rc);
 		return rc;
+	}
+	rc = sid_to_id(cifs_sb, owner_sid_ptr, fattr, SIDOWNER);
+	if (rc) {
+		cFYI(1, "%s: Error %d mapping Owner SID to uid", __func__, rc);
+		return rc;
+	}
 
 	rc = parse_sid(group_sid_ptr, end_of_acl);
-	if (rc)
+	if (rc) {
+		cFYI(1, "%s: Error %d mapping Owner SID to gid", __func__, rc);
 		return rc;
+	}
+	rc = sid_to_id(cifs_sb, group_sid_ptr, fattr, SIDGROUP);
+	if (rc) {
+		cFYI(1, "%s: Error %d mapping Group SID to gid", __func__, rc);
+		return rc;
+	}
 
 	if (dacloffset)
 		parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr,
@@ -658,7 +918,7 @@  static int parse_sec_desc(struct cifs_ntsd *pntsd, int acl_len,
 	memcpy((void *)(&(cifscred->gsid)), (void *)group_sid_ptr,
 			sizeof(struct cifs_sid)); */
 
-	return 0;
+	return rc;
 }
 
 
@@ -865,7 +1125,7 @@  cifs_acl_to_fattr(struct cifs_sb_info *cifs_sb, struct cifs_fattr *fattr,
 		rc = PTR_ERR(pntsd);
 		cERROR(1, "%s: error %d getting sec desc", __func__, rc);
 	} else {
-		rc = parse_sec_desc(pntsd, acllen, fattr);
+		rc = parse_sec_desc(cifs_sb, pntsd, acllen, fattr);
 		kfree(pntsd);
 		if (rc)
 			cERROR(1, "parse sec desc failed rc = %d", rc);
diff --git a/fs/cifs/cifsacl.h b/fs/cifs/cifsacl.h
index c4ae7d0..a30b19c 100644
--- a/fs/cifs/cifsacl.h
+++ b/fs/cifs/cifsacl.h
@@ -39,6 +39,15 @@ 
 #define ACCESS_ALLOWED	0
 #define ACCESS_DENIED	1
 
+#define SIDOWNER 1
+#define SIDGROUP 2
+#define SIDLEN 150 /* S- 1 revision- 6 authorities- max 5 sub authorities */
+
+#define SID_ID_MAPPED 0
+#define SID_ID_PENDING 1
+#define SID_MAP_EXPIRE 1000 /* enough for an upcall to return? */
+#define SID_MAP_RETRY 1000  /* wait for next attempt to map sid */
+
 struct cifs_ntsd {
 	__le16 revision; /* revision level */
 	__le16 type;
@@ -74,6 +83,21 @@  struct cifs_wksid {
 	char sidname[SIDNAMELENGTH];
 } __attribute__((packed));
 
+struct cifs_sid_id {
+	unsigned long id;
+	unsigned long time;
+	unsigned long retry;
+	unsigned long state;
+	char *sidstr;
+	struct rb_node rbnode;
+	struct cifs_sid sid;
+};
+
+#ifdef __KERNEL__
+extern struct key_type cifs_idmap_key_type;
+extern const struct cred *root_cred;
+#endif /* KERNEL */
+
 extern int match_sid(struct cifs_sid *);
 extern int compare_sids(const struct cifs_sid *, const struct cifs_sid *);