ceph: handle cap import atomically

cap import messages are processed by both handle_cap_import() and
handle_cap_grant(). These two functions are not executed in the same
atomic context, so they can races with cap release.

The fix is make handle_cap_import() not release the i_ceph_lock when
it returns. Let handle_cap_grant() release the lock after it finishes
its job.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>

1 files changed, 54 insertions, 45 deletions

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 73a42f504357..9f2c99c34e92 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2379,23 +2379,20 @@ static void invalidate_aliases(struct inode *inode)
  * actually be a revocation if it specifies a smaller cap set.)
  *
  * caller holds s_mutex and i_ceph_lock, we drop both.
- *
- * return value:
- *  0 - ok
- *  1 - check_caps on auth cap only (writeback)
- *  2 - check_caps (ack revoke)
  */
-static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
+static void handle_cap_grant(struct ceph_mds_client *mdsc,
+                             struct inode *inode, struct ceph_mds_caps *grant,
+                             void *snaptrace, int snaptrace_len,
+                             struct ceph_buffer *xattr_buf,
                              struct ceph_mds_session *session,
-                             struct ceph_cap *cap,
-                             struct ceph_buffer *xattr_buf)
-                __releases(ci->i_ceph_lock)
+                             struct ceph_cap *cap, int issued)
+        __releases(ci->i_ceph_lock)
 {
         struct ceph_inode_info *ci = ceph_inode(inode);
         int mds = session->s_mds;
         int seq = le32_to_cpu(grant->seq);
         int newcaps = le32_to_cpu(grant->caps);
-        int issued, implemented, used, wanted, dirty;
+        int used, wanted, dirty;
         u64 size = le64_to_cpu(grant->size);
         u64 max_size = le64_to_cpu(grant->max_size);
         struct timespec mtime, atime, ctime;
@@ -2449,10 +2446,6 @@ static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
         }
 
         /* side effects now are allowed */
-
-        issued = __ceph_caps_issued(ci, &implemented);
-        issued |= implemented | __ceph_caps_dirty(ci);
-
         cap->cap_gen = session->s_cap_gen;
         cap->seq = seq;
 
@@ -2585,6 +2578,17 @@ static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
 
         spin_unlock(&ci->i_ceph_lock);
 
+        if (le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT) {
+                down_write(&mdsc->snap_rwsem);
+                ceph_update_snap_trace(mdsc, snaptrace,
+                                       snaptrace + snaptrace_len, false);
+                downgrade_write(&mdsc->snap_rwsem);
+                kick_flushing_inode_caps(mdsc, session, inode);
+                up_read(&mdsc->snap_rwsem);
+                if (newcaps & ~issued)
+                        wake = 1;
+        }
+
         if (queue_trunc) {
                 ceph_queue_vmtruncate(inode);
                 ceph_queue_revalidate(inode);
@@ -2886,21 +2890,22 @@ out_unlock:
 }
 
 /*
- * Handle cap IMPORT.  If there are temp bits from an older EXPORT,
- * clean them up.
+ * Handle cap IMPORT.
  *
- * caller holds s_mutex.
+ * caller holds s_mutex. acquires i_ceph_lock
  */
 static void handle_cap_import(struct ceph_mds_client *mdsc,
                               struct inode *inode, struct ceph_mds_caps *im,
                               struct ceph_mds_cap_peer *ph,
                               struct ceph_mds_session *session,
-                              void *snaptrace, int snaptrace_len)
+                              struct ceph_cap **target_cap, int *old_issued)
+        __acquires(ci->i_ceph_lock)
 {
         struct ceph_inode_info *ci = ceph_inode(inode);
-        struct ceph_cap *cap, *new_cap = NULL;
+        struct ceph_cap *cap, *ocap, *new_cap = NULL;
         int mds = session->s_mds;
-        unsigned issued = le32_to_cpu(im->caps);
+        int issued;
+        unsigned caps = le32_to_cpu(im->caps);
         unsigned wanted = le32_to_cpu(im->wanted);
         unsigned seq = le32_to_cpu(im->seq);
         unsigned mseq = le32_to_cpu(im->migrate_seq);
@@ -2929,44 +2934,43 @@ retry:
                         new_cap = ceph_get_cap(mdsc, NULL);
                         goto retry;
                 }
+                cap = new_cap;
+        } else {
+                if (new_cap) {
+                        ceph_put_cap(mdsc, new_cap);
+                        new_cap = NULL;
+                }
         }
 
-        ceph_add_cap(inode, session, cap_id, -1, issued, wanted, seq, mseq,
+        __ceph_caps_issued(ci, &issued);
+        issued |= __ceph_caps_dirty(ci);
+
+        ceph_add_cap(inode, session, cap_id, -1, caps, wanted, seq, mseq,
                      realmino, CEPH_CAP_FLAG_AUTH, &new_cap);
 
-        cap = peer >= 0 ? __get_cap_for_mds(ci, peer) : NULL;
-        if (cap && cap->cap_id == p_cap_id) {
+        ocap = peer >= 0 ? __get_cap_for_mds(ci, peer) : NULL;
+        if (ocap && ocap->cap_id == p_cap_id) {
                 dout(" remove export cap %p mds%d flags %d\n",
-                     cap, peer, ph->flags);
+                     ocap, peer, ph->flags);
                 if ((ph->flags & CEPH_CAP_FLAG_AUTH) &&
-                    (cap->seq != le32_to_cpu(ph->seq) ||
-                     cap->mseq != le32_to_cpu(ph->mseq))) {
+                    (ocap->seq != le32_to_cpu(ph->seq) ||
+                     ocap->mseq != le32_to_cpu(ph->mseq))) {
                         pr_err("handle_cap_import: mismatched seq/mseq: "
                                "ino (%llx.%llx) mds%d seq %d mseq %d "
                                "importer mds%d has peer seq %d mseq %d\n",
-                               ceph_vinop(inode), peer, cap->seq,
-                               cap->mseq, mds, le32_to_cpu(ph->seq),
+                               ceph_vinop(inode), peer, ocap->seq,
+                               ocap->mseq, mds, le32_to_cpu(ph->seq),
                                le32_to_cpu(ph->mseq));
                 }
-                __ceph_remove_cap(cap, (ph->flags & CEPH_CAP_FLAG_RELEASE));
+                __ceph_remove_cap(ocap, (ph->flags & CEPH_CAP_FLAG_RELEASE));
         }
 
         /* make sure we re-request max_size, if necessary */
         ci->i_wanted_max_size = 0;
         ci->i_requested_max_size = 0;
-        spin_unlock(&ci->i_ceph_lock);
-
-        wake_up_all(&ci->i_cap_wq);
 
-        down_write(&mdsc->snap_rwsem);
-        ceph_update_snap_trace(mdsc, snaptrace, snaptrace+snaptrace_len,
-                               false);
-        downgrade_write(&mdsc->snap_rwsem);
-        kick_flushing_inode_caps(mdsc, session, inode);
-        up_read(&mdsc->snap_rwsem);
-
-        if (new_cap)
-                ceph_put_cap(mdsc, new_cap);
+        *old_issued = issued;
+        *target_cap = cap;
 }
 
 /*
@@ -2986,7 +2990,7 @@ void ceph_handle_caps(struct ceph_mds_session *session,
         struct ceph_mds_caps *h;
         struct ceph_mds_cap_peer *peer = NULL;
         int mds = session->s_mds;
-        int op;
+        int op, issued;
         u32 seq, mseq;
         struct ceph_vino vino;
         u64 cap_id;
@@ -3078,7 +3082,10 @@ void ceph_handle_caps(struct ceph_mds_session *session,
 
         case CEPH_CAP_OP_IMPORT:
                 handle_cap_import(mdsc, inode, h, peer, session,
-                                  snaptrace, snaptrace_len);
+                                  &cap, &issued);
+                handle_cap_grant(mdsc, inode, h,  snaptrace, snaptrace_len,
+                                 msg->middle, session, cap, issued);
+                goto done_unlocked;
         }
 
         /* the rest require a cap */
@@ -3095,8 +3102,10 @@ void ceph_handle_caps(struct ceph_mds_session *session,
         switch (op) {
         case CEPH_CAP_OP_REVOKE:
         case CEPH_CAP_OP_GRANT:
-        case CEPH_CAP_OP_IMPORT:
-                handle_cap_grant(inode, h, session, cap, msg->middle);
+                __ceph_caps_issued(ci, &issued);
+                issued |= __ceph_caps_dirty(ci);
+                handle_cap_grant(mdsc, inode, h, NULL, 0, msg->middle,
+                                 session, cap, issued);
                 goto done_unlocked;
 
         case CEPH_CAP_OP_FLUSH_ACK: