ceph: record truncate size/seq for snap data writeback

Dirty snapshot data needs to be flushed unconditionally. If they
were created before truncation, writeback should use old truncate
size/seq.
Signed-off-by: Yan, Zheng <zyan@redhat.com>

fs/ceph/addr.c

@@ -474,7 +474,9 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
  * only snap context we are allowed to write back.
  */
 static struct ceph_snap_context *get_oldest_context(struct inode *inode,
-						    loff_t *snap_size)
+						    loff_t *snap_size,
+						    u64 *truncate_size,
+						    u32 *truncate_seq)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	struct ceph_snap_context *snapc = NULL;
@@ -488,6 +490,10 @@ static struct ceph_snap_context *get_oldest_context(struct inode *inode,
 			snapc = ceph_get_snap_context(capsnap->context);
 			if (snap_size)
 				*snap_size = capsnap->size;
+			if (truncate_size)
+				*truncate_size = capsnap->truncate_size;
+			if (truncate_seq)
+				*truncate_seq = capsnap->truncate_seq;
 			break;
 		}
 	}
@@ -495,6 +501,10 @@ static struct ceph_snap_context *get_oldest_context(struct inode *inode,
 		snapc = ceph_get_snap_context(ci->i_head_snapc);
 		dout(" head snapc %p has %d dirty pages\n",
 		     snapc, ci->i_wrbuffer_ref_head);
+		if (truncate_size)
+			*truncate_size = capsnap->truncate_size;
+		if (truncate_seq)
+			*truncate_seq = capsnap->truncate_seq;
 	}
 	spin_unlock(&ci->i_ceph_lock);
 	return snapc;
@@ -537,7 +547,8 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 		dout("writepage %p page %p not dirty?\n", inode, page);
 		goto out;
 	}
-	oldest = get_oldest_context(inode, &snap_size);
+	oldest = get_oldest_context(inode, &snap_size,
+				    &truncate_size, &truncate_seq);
 	if (snapc->seq > oldest->seq) {
 		dout("writepage %p page %p snapc %p not writeable - noop\n",
 		     inode, page, snapc);
@@ -548,12 +559,8 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 	}
 	ceph_put_snap_context(oldest);
 
-	spin_lock(&ci->i_ceph_lock);
-	truncate_seq = ci->i_truncate_seq;
-	truncate_size = ci->i_truncate_size;
 	if (snap_size == -1)
 		snap_size = i_size_read(inode);
-	spin_unlock(&ci->i_ceph_lock);
 
 	/* is this a partial page at end of file? */
 	if (page_off >= snap_size) {
@@ -800,7 +807,8 @@ static int ceph_writepages_start(struct address_space *mapping,
 	/* find oldest snap context with dirty data */
 	ceph_put_snap_context(snapc);
 	snap_size = -1;
-	snapc = get_oldest_context(inode, &snap_size);
+	snapc = get_oldest_context(inode, &snap_size,
+				   &truncate_size, &truncate_seq);
 	if (!snapc) {
 		/* hmm, why does writepages get called when there
 		   is no dirty data? */
@@ -810,11 +818,7 @@ static int ceph_writepages_start(struct address_space *mapping,
 	dout(" oldest snapc is %p seq %lld (%d snaps)\n",
 	     snapc, snapc->seq, snapc->num_snaps);
 
-	spin_lock(&ci->i_ceph_lock);
-	truncate_seq = ci->i_truncate_seq;
-	truncate_size = ci->i_truncate_size;
 	i_size = i_size_read(inode);
-	spin_unlock(&ci->i_ceph_lock);
 
 	if (last_snapc && snapc != last_snapc) {
 		/* if we switched to a newer snapc, restart our scan at the
@@ -1160,7 +1164,8 @@ static int ceph_writepages_start(struct address_space *mapping,
 static int context_is_writeable_or_written(struct inode *inode,
 					   struct ceph_snap_context *snapc)
 {
-	struct ceph_snap_context *oldest = get_oldest_context(inode, NULL);
+	struct ceph_snap_context *oldest = get_oldest_context(inode, NULL,
+							      NULL, NULL);
 	int ret = !oldest || snapc->seq <= oldest->seq;
 
 	ceph_put_snap_context(oldest);
@@ -1205,7 +1210,7 @@ static int ceph_update_writeable_page(struct file *file,
 		 * this page is already dirty in another (older) snap
 		 * context!  is it writeable now?
 		 */
-		oldest = get_oldest_context(inode, NULL);
+		oldest = get_oldest_context(inode, NULL, NULL, NULL);
 
 		if (snapc->seq > oldest->seq) {
 			ceph_put_snap_context(oldest);

fs/ceph/snap.c

@@ -593,6 +593,8 @@ int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
 	capsnap->atime = inode->i_atime;
 	capsnap->ctime = inode->i_ctime;
 	capsnap->time_warp_seq = ci->i_time_warp_seq;
+	capsnap->truncate_size = ci->i_truncate_size;
+	capsnap->truncate_seq = ci->i_truncate_seq;
 	if (capsnap->dirty_pages) {
 		dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
 		     "still has %d dirty pages\n", inode, capsnap,

fs/ceph/super.h

@@ -181,6 +181,8 @@ struct ceph_cap_snap {
 	u64 size;
 	struct timespec mtime, atime, ctime;
 	u64 time_warp_seq;
+	u64 truncate_size;
+	u32 truncate_seq;
 	int writing;   /* a sync write is still in progress */
 	int dirty_pages;     /* dirty pages awaiting writeback */
 	bool inline_data;