ceph: cleanup return error of try_get_cap_refs()

Returns 0 if caps were not able to be acquired (yet), 1 if cap
acquisition succeeded, or a negative error code. There are 3 special
error codes:

-EAGAIN: need to sleep but non-blocking is specified
-EFBIG:  ask caller to call check_max_size() and try again.
-ESTALE: ask caller to call ceph_renew_caps() and try again.

[ jlayton: add WARN_ON_ONCE check for -EAGAIN ]

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 342a32c..78a3050 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2530,10 +2530,11 @@ void ceph_take_cap_refs(struct ceph_inode_info *ci, int got,
  * Note that caller is responsible for ensuring max_size increases are
  * requested from the MDS.
  *
- * Returns 0 if caps were not able to be acquired (yet), a 1 if they were,
- * or a negative error code.
- *
- * FIXME: how does a 0 return differ from -EAGAIN?
+ * Returns 0 if caps were not able to be acquired (yet), 1 if succeed,
+ * or a negative error code. There are 3 speical error codes:
+ *  -EAGAIN: need to sleep but non-blocking is specified
+ *  -EFBIG:  ask caller to call check_max_size() and try again.
+ *  -ESTALE: ask caller to call ceph_renew_caps() and try again.
  */
 enum {
        /* first 8 bits are reserved for CEPH_FILE_MODE_FOO */
@@ -2581,7 +2582,7 @@ again:
                        dout("get_cap_refs %p endoff %llu > maxsize %llu\n",
                             inode, endoff, ci->i_max_size);
                        if (endoff > ci->i_requested_max_size)
-                               ret = -EAGAIN;
+                               ret = -EFBIG;
                        goto out_unlock;
                }
                /*
@@ -2743,7 +2744,10 @@ int ceph_try_get_caps(struct inode *inode, int need, int want,
                flags |= NON_BLOCKING;
 
        ret = try_get_cap_refs(inode, need, want, 0, flags, got);
-       return ret == -EAGAIN ? 0 : ret;
+       /* three special error codes */
+       if (ret == -EAGAIN || ret == -EFBIG || ret == -EAGAIN)
+               ret = 0;
+       return ret;
 }
 
 /*
@@ -2771,17 +2775,13 @@ int ceph_get_caps(struct file *filp, int need, int want,
        flags = get_used_fmode(need | want);
 
        while (true) {
-               if (endoff > 0)
-                       check_max_size(inode, endoff);
-
                flags &= CEPH_FILE_MODE_MASK;
                if (atomic_read(&fi->num_locks))
                        flags |= CHECK_FILELOCK;
                _got = 0;
                ret = try_get_cap_refs(inode, need, want, endoff,
                                       flags, &_got);
-               if (ret == -EAGAIN)
-                       continue;
+               WARN_ON_ONCE(ret == -EAGAIN);
                if (!ret) {
                        struct ceph_mds_client *mdsc = fsc->mdsc;
                        struct cap_wait cw;
@@ -2829,6 +2829,10 @@ int ceph_get_caps(struct file *filp, int need, int want,
                }
 
                if (ret < 0) {
+                       if (ret == -EFBIG) {
+                               check_max_size(inode, endoff);
+                               continue;
+                       }
                        if (ret == -ESTALE) {
                                /* session was killed, try renew caps */
                                ret = ceph_renew_caps(inode, flags);