ceph: don't use truncate_pagecache() to invalidate read cache

truncate_pagecache() drops dirty pages, it's dangerous to use it
to invalidate read cache. Besides, we shouldn't start invalidating
read cache while there are buffer writers. Because buffer writers
may add dirty pages later.
Signed-off-by: Yan, Zheng <zyan@redhat.com>

fs/ceph/caps.c

@@ -1656,7 +1656,7 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,
 	 */
 	if ((!is_delayed || mdsc->stopping) &&
 	    !S_ISDIR(inode->i_mode) &&		/* ignore readdir cache */
-	    ci->i_wrbuffer_ref == 0 &&		/* no dirty pages... */
+	    !(ci->i_wb_ref || ci->i_wrbuffer_ref) &&   /* no dirty pages... */
 	    inode->i_data.nrpages &&		/* have cached pages */
 	    (revoking & (CEPH_CAP_FILE_CACHE|
 			 CEPH_CAP_FILE_LAZYIO)) && /*  or revoking cache */
@@ -1698,8 +1698,8 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,
 
 		revoking = cap->implemented & ~cap->issued;
 		dout(" mds%d cap %p used %s issued %s implemented %s revoking %s\n",
-		     cap->mds, cap, ceph_cap_string(cap->issued),
-		     ceph_cap_string(cap_used),
+		     cap->mds, cap, ceph_cap_string(cap_used),
+		     ceph_cap_string(cap->issued),
 		     ceph_cap_string(cap->implemented),
 		     ceph_cap_string(revoking));
 
@@ -2828,7 +2828,7 @@ static void handle_cap_grant(struct ceph_mds_client *mdsc,
 	if (!S_ISDIR(inode->i_mode) && /* don't invalidate readdir cache */
 	    ((cap->issued & ~newcaps) & CEPH_CAP_FILE_CACHE) &&
 	    (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
-	    !ci->i_wrbuffer_ref) {
+	    !(ci->i_wrbuffer_ref || ci->i_wb_ref)) {
 		if (try_nonblocking_invalidate(inode)) {
 			/* there were locked pages.. invalidate later
 			   in a separate thread. */

fs/ceph/inode.c

@@ -1728,7 +1728,9 @@ static void ceph_invalidate_work(struct work_struct *work)
 	orig_gen = ci->i_rdcache_gen;
 	spin_unlock(&ci->i_ceph_lock);
 
-	truncate_pagecache(inode, 0);
+	if (invalidate_inode_pages2(inode->i_mapping) < 0) {
+		pr_err("invalidate_pages %p fails\n", inode);
+	}
 
 	spin_lock(&ci->i_ceph_lock);
 	if (orig_gen == ci->i_rdcache_gen &&