This is a note to let you know that I've just added the patch titled
cifs: avoid potential races when handling multiple dfs tcons
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cifs-avoid-potential-races-when-handling-multiple-df.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 06b40962ef4b3b27036a69101a893fb148fcd25c
Author: Paulo Alcantara <pc@xxxxxxxxxxxxx>
Date: Thu Apr 27 04:40:08 2023 -0300
cifs: avoid potential races when handling multiple dfs tcons
[ Upstream commit 6be2ea33a4093402252724a00c4af8033725184c ]
Now that a DFS tcon manages its own list of DFS referrals and
sessions, there is no point in having a single worker to refresh
referrals of all DFS tcons. Make it faster and less prone to race
conditions when having several mounts by queueing a worker per DFS
tcon that will take care of refreshing only the DFS referrals related
to it.
Cc: stable@xxxxxxxxxxxxxxx # v6.2+
Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index ea216e9d0f944..e6d12a6563887 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1244,8 +1244,8 @@ struct cifs_tcon {
struct cached_fids *cfids;
/* BB add field for back pointer to sb struct(s)? */
#ifdef CONFIG_CIFS_DFS_UPCALL
- struct list_head ulist; /* cache update list */
struct list_head dfs_ses_list;
+ struct delayed_work dfs_cache_work;
#endif
struct delayed_work query_interfaces; /* query interfaces workqueue job */
};
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index af491ae70678a..d71c2fb117c9e 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2386,6 +2386,9 @@ cifs_put_tcon(struct cifs_tcon *tcon)
/* cancel polling of interfaces */
cancel_delayed_work_sync(&tcon->query_interfaces);
+#ifdef CONFIG_CIFS_DFS_UPCALL
+ cancel_delayed_work_sync(&tcon->dfs_cache_work);
+#endif
if (tcon->use_witness) {
int rc;
@@ -2633,7 +2636,9 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
(SMB_INTERFACE_POLL_INTERVAL * HZ));
}
-
+#ifdef CONFIG_CIFS_DFS_UPCALL
+ INIT_DELAYED_WORK(&tcon->dfs_cache_work, dfs_cache_refresh);
+#endif
spin_lock(&cifs_tcp_ses_lock);
list_add(&tcon->tcon_list, &ses->tcon_list);
spin_unlock(&cifs_tcp_ses_lock);
diff --git a/fs/cifs/dfs.c b/fs/cifs/dfs.c
index f02f8d3b92ee8..a93dbca1411b2 100644
--- a/fs/cifs/dfs.c
+++ b/fs/cifs/dfs.c
@@ -157,6 +157,8 @@ static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, co
rc = cifs_is_path_remote(mnt_ctx);
}
+ dfs_cache_noreq_update_tgthint(ref_path + 1, tit);
+
if (rc == -EREMOTE && is_refsrv) {
rc2 = add_root_smb_session(mnt_ctx);
if (rc2)
@@ -259,6 +261,8 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
if (list_empty(&tcon->dfs_ses_list)) {
list_replace_init(&mnt_ctx->dfs_ses_list,
&tcon->dfs_ses_list);
+ queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
+ dfs_cache_get_ttl() * HZ);
} else {
dfs_put_root_smb_sessions(&mnt_ctx->dfs_ses_list);
}
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index 6557d7b2798a0..1513b2709889b 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -20,12 +20,14 @@
#include "cifs_unicode.h"
#include "smb2glob.h"
#include "dns_resolve.h"
+#include "dfs.h"
#include "dfs_cache.h"
-#define CACHE_HTABLE_SIZE 32
-#define CACHE_MAX_ENTRIES 64
-#define CACHE_MIN_TTL 120 /* 2 minutes */
+#define CACHE_HTABLE_SIZE 32
+#define CACHE_MAX_ENTRIES 64
+#define CACHE_MIN_TTL 120 /* 2 minutes */
+#define CACHE_DEFAULT_TTL 300 /* 5 minutes */
#define IS_DFS_INTERLINK(v) (((v) & DFSREF_REFERRAL_SERVER) && !((v) & DFSREF_STORAGE_SERVER))
@@ -50,10 +52,9 @@ struct cache_entry {
};
static struct kmem_cache *cache_slab __read_mostly;
-static struct workqueue_struct *dfscache_wq __read_mostly;
+struct workqueue_struct *dfscache_wq;
-static int cache_ttl;
-static DEFINE_SPINLOCK(cache_ttl_lock);
+atomic_t dfs_cache_ttl;
static struct nls_table *cache_cp;
@@ -65,10 +66,6 @@ static atomic_t cache_count;
static struct hlist_head cache_htable[CACHE_HTABLE_SIZE];
static DECLARE_RWSEM(htable_rw_lock);
-static void refresh_cache_worker(struct work_struct *work);
-
-static DECLARE_DELAYED_WORK(refresh_task, refresh_cache_worker);
-
/**
* dfs_cache_canonical_path - get a canonical DFS path
*
@@ -290,7 +287,9 @@ int dfs_cache_init(void)
int rc;
int i;
- dfscache_wq = alloc_workqueue("cifs-dfscache", WQ_FREEZABLE | WQ_UNBOUND, 1);
+ dfscache_wq = alloc_workqueue("cifs-dfscache",
+ WQ_UNBOUND|WQ_FREEZABLE|WQ_MEM_RECLAIM,
+ 0);
if (!dfscache_wq)
return -ENOMEM;
@@ -306,6 +305,7 @@ int dfs_cache_init(void)
INIT_HLIST_HEAD(&cache_htable[i]);
atomic_set(&cache_count, 0);
+ atomic_set(&dfs_cache_ttl, CACHE_DEFAULT_TTL);
cache_cp = load_nls("utf8");
if (!cache_cp)
cache_cp = load_nls_default();
@@ -480,6 +480,7 @@ static struct cache_entry *add_cache_entry_locked(struct dfs_info3_param *refs,
int rc;
struct cache_entry *ce;
unsigned int hash;
+ int ttl;
WARN_ON(!rwsem_is_locked(&htable_rw_lock));
@@ -496,15 +497,8 @@ static struct cache_entry *add_cache_entry_locked(struct dfs_info3_param *refs,
if (IS_ERR(ce))
return ce;
- spin_lock(&cache_ttl_lock);
- if (!cache_ttl) {
- cache_ttl = ce->ttl;
- queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
- } else {
- cache_ttl = min_t(int, cache_ttl, ce->ttl);
- mod_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
- }
- spin_unlock(&cache_ttl_lock);
+ ttl = min_t(int, atomic_read(&dfs_cache_ttl), ce->ttl);
+ atomic_set(&dfs_cache_ttl, ttl);
hlist_add_head(&ce->hlist, &cache_htable[hash]);
dump_ce(ce);
@@ -616,7 +610,6 @@ static struct cache_entry *lookup_cache_entry(const char *path)
*/
void dfs_cache_destroy(void)
{
- cancel_delayed_work_sync(&refresh_task);
unload_nls(cache_cp);
flush_cache_ents();
kmem_cache_destroy(cache_slab);
@@ -1142,6 +1135,7 @@ static bool target_share_equal(struct TCP_Server_Info *server, const char *s1, c
* target shares in @refs.
*/
static void mark_for_reconnect_if_needed(struct TCP_Server_Info *server,
+ const char *path,
struct dfs_cache_tgt_list *old_tl,
struct dfs_cache_tgt_list *new_tl)
{
@@ -1153,8 +1147,10 @@ static void mark_for_reconnect_if_needed(struct TCP_Server_Info *server,
nit = dfs_cache_get_next_tgt(new_tl, nit)) {
if (target_share_equal(server,
dfs_cache_get_tgt_name(oit),
- dfs_cache_get_tgt_name(nit)))
+ dfs_cache_get_tgt_name(nit))) {
+ dfs_cache_noreq_update_tgthint(path, nit);
return;
+ }
}
}
@@ -1162,13 +1158,28 @@ static void mark_for_reconnect_if_needed(struct TCP_Server_Info *server,
cifs_signal_cifsd_for_reconnect(server, true);
}
+static bool is_ses_good(struct cifs_ses *ses)
+{
+ struct TCP_Server_Info *server = ses->server;
+ struct cifs_tcon *tcon = ses->tcon_ipc;
+ bool ret;
+
+ spin_lock(&ses->ses_lock);
+ spin_lock(&ses->chan_lock);
+ ret = !cifs_chan_needs_reconnect(ses, server) &&
+ ses->ses_status == SES_GOOD &&
+ !tcon->need_reconnect;
+ spin_unlock(&ses->chan_lock);
+ spin_unlock(&ses->ses_lock);
+ return ret;
+}
+
/* Refresh dfs referral of tcon and mark it for reconnect if needed */
-static int __refresh_tcon(const char *path, struct cifs_tcon *tcon, bool force_refresh)
+static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_refresh)
{
struct dfs_cache_tgt_list old_tl = DFS_CACHE_TGT_LIST_INIT(old_tl);
struct dfs_cache_tgt_list new_tl = DFS_CACHE_TGT_LIST_INIT(new_tl);
- struct cifs_ses *ses = CIFS_DFS_ROOT_SES(tcon->ses);
- struct cifs_tcon *ipc = ses->tcon_ipc;
+ struct TCP_Server_Info *server = ses->server;
bool needs_refresh = false;
struct cache_entry *ce;
unsigned int xid;
@@ -1190,20 +1201,19 @@ static int __refresh_tcon(const char *path, struct cifs_tcon *tcon, bool force_r
goto out;
}
- spin_lock(&ipc->tc_lock);
- if (ipc->status != TID_GOOD) {
- spin_unlock(&ipc->tc_lock);
- cifs_dbg(FYI, "%s: skip cache refresh due to disconnected ipc\n", __func__);
+ ses = CIFS_DFS_ROOT_SES(ses);
+ if (!is_ses_good(ses)) {
+ cifs_dbg(FYI, "%s: skip cache refresh due to disconnected ipc\n",
+ __func__);
goto out;
}
- spin_unlock(&ipc->tc_lock);
ce = cache_refresh_path(xid, ses, path, true);
if (!IS_ERR(ce)) {
rc = get_targets(ce, &new_tl);
up_read(&htable_rw_lock);
cifs_dbg(FYI, "%s: get_targets: %d\n", __func__, rc);
- mark_for_reconnect_if_needed(tcon->ses->server, &old_tl, &new_tl);
+ mark_for_reconnect_if_needed(server, path, &old_tl, &new_tl);
}
out:
@@ -1216,10 +1226,11 @@ static int __refresh_tcon(const char *path, struct cifs_tcon *tcon, bool force_r
static int refresh_tcon(struct cifs_tcon *tcon, bool force_refresh)
{
struct TCP_Server_Info *server = tcon->ses->server;
+ struct cifs_ses *ses = tcon->ses;
mutex_lock(&server->refpath_lock);
if (server->leaf_fullpath)
- __refresh_tcon(server->leaf_fullpath + 1, tcon, force_refresh);
+ __refresh_tcon(server->leaf_fullpath + 1, ses, force_refresh);
mutex_unlock(&server->refpath_lock);
return 0;
}
@@ -1263,60 +1274,32 @@ int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb)
return refresh_tcon(tcon, true);
}
-/*
- * Worker that will refresh DFS cache from all active mounts based on lowest TTL value
- * from a DFS referral.
- */
-static void refresh_cache_worker(struct work_struct *work)
+/* Refresh all DFS referrals related to DFS tcon */
+void dfs_cache_refresh(struct work_struct *work)
{
struct TCP_Server_Info *server;
- struct cifs_tcon *tcon, *ntcon;
- struct list_head tcons;
+ struct dfs_root_ses *rses;
+ struct cifs_tcon *tcon;
struct cifs_ses *ses;
- INIT_LIST_HEAD(&tcons);
+ tcon = container_of(work, struct cifs_tcon, dfs_cache_work.work);
+ ses = tcon->ses;
+ server = ses->server;
- spin_lock(&cifs_tcp_ses_lock);
- list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {
- spin_lock(&server->srv_lock);
- if (!server->leaf_fullpath) {
- spin_unlock(&server->srv_lock);
- continue;
- }
- spin_unlock(&server->srv_lock);
-
- list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
- if (ses->tcon_ipc) {
- ses->ses_count++;
- list_add_tail(&ses->tcon_ipc->ulist, &tcons);
- }
- list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
- if (!tcon->ipc) {
- tcon->tc_count++;
- list_add_tail(&tcon->ulist, &tcons);
- }
- }
- }
- }
- spin_unlock(&cifs_tcp_ses_lock);
-
- list_for_each_entry_safe(tcon, ntcon, &tcons, ulist) {
- struct TCP_Server_Info *server = tcon->ses->server;
-
- list_del_init(&tcon->ulist);
+ mutex_lock(&server->refpath_lock);
+ if (server->leaf_fullpath)
+ __refresh_tcon(server->leaf_fullpath + 1, ses, false);
+ mutex_unlock(&server->refpath_lock);
+ list_for_each_entry(rses, &tcon->dfs_ses_list, list) {
+ ses = rses->ses;
+ server = ses->server;
mutex_lock(&server->refpath_lock);
if (server->leaf_fullpath)
- __refresh_tcon(server->leaf_fullpath + 1, tcon, false);
+ __refresh_tcon(server->leaf_fullpath + 1, ses, false);
mutex_unlock(&server->refpath_lock);
-
- if (tcon->ipc)
- cifs_put_smb_ses(tcon->ses);
- else
- cifs_put_tcon(tcon);
}
- spin_lock(&cache_ttl_lock);
- queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
- spin_unlock(&cache_ttl_lock);
+ queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
+ atomic_read(&dfs_cache_ttl) * HZ);
}
diff --git a/fs/cifs/dfs_cache.h b/fs/cifs/dfs_cache.h
index e0d39393035a9..c6d89cd6d4fd7 100644
--- a/fs/cifs/dfs_cache.h
+++ b/fs/cifs/dfs_cache.h
@@ -13,6 +13,9 @@
#include <linux/uuid.h>
#include "cifsglob.h"
+extern struct workqueue_struct *dfscache_wq;
+extern atomic_t dfs_cache_ttl;
+
#define DFS_CACHE_TGT_LIST_INIT(var) { .tl_numtgts = 0, .tl_list = LIST_HEAD_INIT((var).tl_list), }
struct dfs_cache_tgt_list {
@@ -42,6 +45,7 @@ int dfs_cache_get_tgt_share(char *path, const struct dfs_cache_tgt_iterator *it,
char **prefix);
char *dfs_cache_canonical_path(const char *path, const struct nls_table *cp, int remap);
int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb);
+void dfs_cache_refresh(struct work_struct *work);
static inline struct dfs_cache_tgt_iterator *
dfs_cache_get_next_tgt(struct dfs_cache_tgt_list *tl,
@@ -89,4 +93,9 @@ dfs_cache_get_nr_tgts(const struct dfs_cache_tgt_list *tl)
return tl ? tl->tl_numtgts : 0;
}
+static inline int dfs_cache_get_ttl(void)
+{
+ return atomic_read(&dfs_cache_ttl);
+}
+
#endif /* _CIFS_DFS_CACHE_H */
