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Commit d8fb02abdc39f92a1066313e2b17047876afa8f9

Authored by Alex Elder
Committed by Sage Weil
1 parent 32852a81bc
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

ceph: create a new session lock to avoid lock inversion 

Lockdep was reporting a possible circular lock dependency in
dentry_lease_is_valid().  That function needs to sample the
session's s_cap_gen and and s_cap_ttl fields coherently, but needs
to do so while holding a dentry lock.  The s_cap_lock field was
being used to protect the two fields, but that can't be taken while
holding a lock on a dentry within the session.

In most cases, the s_cap_gen and s_cap_ttl fields only get operated
on separately.  But in three cases they need to be updated together.
Implement a new lock to protect the spots updating both fields
atomically is required.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Reviewed-by: Sage Weil <sage@newdream.net>

Showing 4 changed files with 14 additions and 9 deletions Side-by-side Diff

... ... @@ -641,10 +641,10 @@
641 641 unsigned long ttl;
642 642 u32 gen;
643 643  
644   - spin_lock(&cap->session->s_cap_lock);
  644 + spin_lock(&cap->session->s_gen_ttl_lock);
645 645 gen = cap->session->s_cap_gen;
646 646 ttl = cap->session->s_cap_ttl;
647   - spin_unlock(&cap->session->s_cap_lock);
  647 + spin_unlock(&cap->session->s_gen_ttl_lock);
648 648  
649 649 if (cap->cap_gen < gen || time_after_eq(jiffies, ttl)) {
650 650 dout("__cap_is_valid %p cap %p issued %s "
... ... @@ -975,10 +975,10 @@
975 975 di = ceph_dentry(dentry);
976 976 if (di && di->lease_session) {
977 977 s = di->lease_session;
978   - spin_lock(&s->s_cap_lock);
  978 + spin_lock(&s->s_gen_ttl_lock);
979 979 gen = s->s_cap_gen;
980 980 ttl = s->s_cap_ttl;
981   - spin_unlock(&s->s_cap_lock);
  981 + spin_unlock(&s->s_gen_ttl_lock);
982 982  
983 983 if (di->lease_gen == gen &&
984 984 time_before(jiffies, dentry->d_time) &&
fs/ceph/mds_client.c
Diff comments   View file @ d8fb02a
... ... @@ -400,9 +400,11 @@
400 400 s->s_con.peer_name.type = CEPH_ENTITY_TYPE_MDS;
401 401 s->s_con.peer_name.num = cpu_to_le64(mds);
402 402  
403   - spin_lock_init(&s->s_cap_lock);
  403 + spin_lock_init(&s->s_gen_ttl_lock);
404 404 s->s_cap_gen = 0;
405 405 s->s_cap_ttl = 0;
  406 +
  407 + spin_lock_init(&s->s_cap_lock);
406 408 s->s_renew_requested = 0;
407 409 s->s_renew_seq = 0;
408 410 INIT_LIST_HEAD(&s->s_caps);
409 411  
... ... @@ -2328,10 +2330,10 @@
2328 2330 case CEPH_SESSION_STALE:
2329 2331 pr_info("mds%d caps went stale, renewing\n",
2330 2332 session->s_mds);
2331   - spin_lock(&session->s_cap_lock);
  2333 + spin_lock(&session->s_gen_ttl_lock);
2332 2334 session->s_cap_gen++;
2333 2335 session->s_cap_ttl = 0;
2334   - spin_unlock(&session->s_cap_lock);
  2336 + spin_unlock(&session->s_gen_ttl_lock);
2335 2337 send_renew_caps(mdsc, session);
2336 2338 break;
2337 2339  
fs/ceph/mds_client.h
Diff comments   View file @ d8fb02a
... ... @@ -117,10 +117,13 @@
117 117 void *s_authorizer_buf, *s_authorizer_reply_buf;
118 118 size_t s_authorizer_buf_len, s_authorizer_reply_buf_len;
119 119  
120   - /* protected by s_cap_lock */
121   - spinlock_t s_cap_lock;
  120 + /* protected by s_gen_ttl_lock */
  121 + spinlock_t s_gen_ttl_lock;
122 122 u32 s_cap_gen; /* inc each time we get mds stale msg */
123 123 unsigned long s_cap_ttl; /* when session caps expire */
  124 +
  125 + /* protected by s_cap_lock */
  126 + spinlock_t s_cap_lock;
124 127 struct list_head s_caps; /* all caps issued by this session */
125 128 int s_nr_caps, s_trim_caps;
126 129 int s_num_cap_releases;