ceph: preallocate flock state without locks held

When the lock_kernel() turns into lock_flocks() and a spinlock, we won't
be able to do allocations with the lock held.  Preallocate space without
the lock, and retry if the lock state changes out from underneath us.

Signed-off-by: Greg Farnum <gregf@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

2 files changed, 44 insertions, 15 deletions

diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c
index 087afe9ca367..40abde93c345 100644
--- a/fs/ceph/locks.c
+++ b/fs/ceph/locks.c
@@ -181,8 +181,9 @@ void ceph_count_locks(struct inode *inode, int *fcntl_count, int *flock_count)
  * Encode the flock and fcntl locks for the given inode into the pagelist.
  * Format is: #fcntl locks, sequential fcntl locks, #flock locks,
  * sequential flock locks.
- * Must be called with BLK already held, and the lock numbers should have
- * been gathered under the same lock holding window.
+ * Must be called with lock_flocks() already held.
+ * If we encounter more of a specific lock type than expected,
+ * we return the value 1.
  */
 int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
                       int num_fcntl_locks, int num_flock_locks)
@@ -190,6 +191,8 @@ int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
         struct file_lock *lock;
         struct ceph_filelock cephlock;
         int err = 0;
+        int seen_fcntl = 0;
+        int seen_flock = 0;
 
         dout("encoding %d flock and %d fcntl locks", num_flock_locks,
              num_fcntl_locks);
@@ -198,6 +201,11 @@ int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
                 goto fail;
         for (lock = inode->i_flock; lock != NULL; lock = lock->fl_next) {
                 if (lock->fl_flags & FL_POSIX) {
+                        ++seen_fcntl;
+                        if (seen_fcntl > num_fcntl_locks) {
+                                err = -ENOSPC;
+                                goto fail;
+                        }
                         err = lock_to_ceph_filelock(lock, &cephlock);
                         if (err)
                                 goto fail;
@@ -213,6 +221,11 @@ int ceph_encode_locks(struct inode *inode, struct ceph_pagelist *pagelist,
                 goto fail;
         for (lock = inode->i_flock; lock != NULL; lock = lock->fl_next) {
                 if (lock->fl_flags & FL_FLOCK) {
+                        ++seen_flock;
+                        if (seen_flock > num_flock_locks) {
+                                err = -ENOSPC;
+                                goto fail;
+                        }
                         err = lock_to_ceph_filelock(lock, &cephlock);
                         if (err)
                                 goto fail;
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 33568239a08e..fbfc298ac55b 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2365,19 +2365,35 @@ static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
 
         if (recon_state->flock) {
                 int num_fcntl_locks, num_flock_locks;
-
-                lock_kernel();
-                ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
-                rec.v2.flock_len = (2*sizeof(u32) +
-                                    (num_fcntl_locks+num_flock_locks) *
-                                    sizeof(struct ceph_filelock));
-
-                err = ceph_pagelist_append(pagelist, &rec, reclen);
-                if (!err)
-                        err = ceph_encode_locks(inode, pagelist,
-                                                num_fcntl_locks,
-                                                num_flock_locks);
-                unlock_kernel();
+                struct ceph_pagelist_cursor trunc_point;
+
+                ceph_pagelist_set_cursor(pagelist, &trunc_point);
+                do {
+                        lock_kernel();
+                        ceph_count_locks(inode, &num_fcntl_locks,
+                                         &num_flock_locks);
+                        rec.v2.flock_len = (2*sizeof(u32) +
+                                            (num_fcntl_locks+num_flock_locks) *
+                                            sizeof(struct ceph_filelock));
+                        unlock_kernel();
+
+                        /* pre-alloc pagelist */
+                        ceph_pagelist_truncate(pagelist, &trunc_point);
+                        err = ceph_pagelist_append(pagelist, &rec, reclen);
+                        if (!err)
+                                err = ceph_pagelist_reserve(pagelist,
+                                                            rec.v2.flock_len);
+
+                        /* encode locks */
+                        if (!err) {
+                                lock_kernel();
+                                err = ceph_encode_locks(inode,
+                                                        pagelist,
+                                                        num_fcntl_locks,
+                                                        num_flock_locks);
+                                unlock_kernel();
+                        }
+                } while (err == -ENOSPC);
         } else {
                 err = ceph_pagelist_append(pagelist, &rec, reclen);
         }