1 files changed, 39 insertions, 34 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 23bb0ce..4125937 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -5,6 +5,7 @@
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/writeback.h>	/* generic_writepages */
+#include <linux/slab.h>
 #include <linux/pagevec.h>
 #include <linux/task_io_accounting_ops.h>
 
@@ -336,16 +337,15 @@ out:
 /*
  * Get ref for the oldest snapc for an inode with dirty data... that is, the
  * only snap context we are allowed to write back.
- *
- * Caller holds i_lock.
  */
-static struct ceph_snap_context *__get_oldest_context(struct inode *inode,
-						      u64 *snap_size)
+static struct ceph_snap_context *get_oldest_context(struct inode *inode,
+						    u64 *snap_size)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	struct ceph_snap_context *snapc = NULL;
 	struct ceph_cap_snap *capsnap = NULL;
 
+	spin_lock(&inode->i_lock);
 	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
 		dout(" cap_snap %p snapc %p has %d dirty pages\n", capsnap,
 		     capsnap->context, capsnap->dirty_pages);
@@ -356,21 +356,11 @@ static struct ceph_snap_context *__get_oldest_context(struct inode *inode,
 			break;
 		}
 	}
-	if (!snapc && ci->i_snap_realm) {
-		snapc = ceph_get_snap_context(ci->i_snap_realm->cached_context);
+	if (!snapc && ci->i_head_snapc) {
+		snapc = ceph_get_snap_context(ci->i_head_snapc);
 		dout(" head snapc %p has %d dirty pages\n",
 		     snapc, ci->i_wrbuffer_ref_head);
 	}
-	return snapc;
-}
-
-static struct ceph_snap_context *get_oldest_context(struct inode *inode,
-						    u64 *snap_size)
-{
-	struct ceph_snap_context *snapc = NULL;
-
-	spin_lock(&inode->i_lock);
-	snapc = __get_oldest_context(inode, snap_size);
 	spin_unlock(&inode->i_lock);
 	return snapc;
 }
@@ -391,7 +381,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 	int len = PAGE_CACHE_SIZE;
 	loff_t i_size;
 	int err = 0;
-	struct ceph_snap_context *snapc;
+	struct ceph_snap_context *snapc, *oldest;
 	u64 snap_size = 0;
 	long writeback_stat;
 
@@ -412,13 +402,16 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 		dout("writepage %p page %p not dirty?\n", inode, page);
 		goto out;
 	}
-	if (snapc != get_oldest_context(inode, &snap_size)) {
+	oldest = get_oldest_context(inode, &snap_size);
+	if (snapc->seq > oldest->seq) {
 		dout("writepage %p page %p snapc %p not writeable - noop\n",
 		     inode, page, (void *)page->private);
 		/* we should only noop if called by kswapd */
 		WARN_ON((current->flags & PF_MEMALLOC) == 0);
+		ceph_put_snap_context(oldest);
 		goto out;
 	}
+	ceph_put_snap_context(oldest);
 
 	/* is this a partial page at end of file? */
 	if (snap_size)
@@ -457,7 +450,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 	ClearPagePrivate(page);
 	end_page_writeback(page);
 	ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
-	ceph_put_snap_context(snapc);
+	ceph_put_snap_context(snapc);  /* page's reference */
 out:
 	return err;
 }
@@ -557,9 +550,9 @@ static void writepages_finish(struct ceph_osd_request *req,
 			dout("inode %p skipping page %p\n", inode, page);
 			wbc->pages_skipped++;
 		}
+		ceph_put_snap_context((void *)page->private);
 		page->private = 0;
 		ClearPagePrivate(page);
-		ceph_put_snap_context(snapc);
 		dout("unlocking %d %p\n", i, page);
 		end_page_writeback(page);
 
@@ -617,7 +610,7 @@ static int ceph_writepages_start(struct address_space *mapping,
 	int range_whole = 0;
 	int should_loop = 1;
 	pgoff_t max_pages = 0, max_pages_ever = 0;
-	struct ceph_snap_context *snapc = NULL, *last_snapc = NULL;
+	struct ceph_snap_context *snapc = NULL, *last_snapc = NULL, *pgsnapc;
 	struct pagevec pvec;
 	int done = 0;
 	int rc = 0;
@@ -769,9 +762,10 @@ get_more_pages:
 			}
 
 			/* only if matching snap context */
-			if (snapc != (void *)page->private) {
-				dout("page snapc %p != oldest %p\n",
-				     (void *)page->private, snapc);
+			pgsnapc = (void *)page->private;
+			if (pgsnapc->seq > snapc->seq) {
+				dout("page snapc %p %lld > oldest %p %lld\n",
+				     pgsnapc, pgsnapc->seq, snapc, snapc->seq);
 				unlock_page(page);
 				if (!locked_pages)
 					continue; /* keep looking for snap */
@@ -913,12 +907,19 @@ 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);
-	return !oldest || snapc->seq <= oldest->seq;
+	int ret = !oldest || snapc->seq <= oldest->seq;
+
+	ceph_put_snap_context(oldest);
+	return ret;
 }
 
 /*
  * We are only allowed to write into/dirty the page if the page is
  * clean, or already dirty within the same snap context.
+ *
+ * called with page locked.
+ * return success with page locked,
+ * or any failure (incl -EAGAIN) with page unlocked.
  */
 static int ceph_update_writeable_page(struct file *file,
 			    loff_t pos, unsigned len,
@@ -931,8 +932,8 @@ static int ceph_update_writeable_page(struct file *file,
 	int pos_in_page = pos & ~PAGE_CACHE_MASK;
 	int end_in_page = pos_in_page + len;
 	loff_t i_size;
-	struct ceph_snap_context *snapc;
 	int r;
+	struct ceph_snap_context *snapc, *oldest;
 
 retry_locked:
 	/* writepages currently holds page lock, but if we change that later, */
@@ -942,30 +943,34 @@ retry_locked:
 	BUG_ON(!ci->i_snap_realm);
 	down_read(&mdsc->snap_rwsem);
 	BUG_ON(!ci->i_snap_realm->cached_context);
-	if (page->private &&
-	    (void *)page->private != ci->i_snap_realm->cached_context) {
+	snapc = (void *)page->private;
+	if (snapc && snapc != ci->i_head_snapc) {
 		/*
 		 * this page is already dirty in another (older) snap
 		 * context!  is it writeable now?
 		 */
-		snapc = get_oldest_context(inode, NULL);
+		oldest = get_oldest_context(inode, NULL);
 		up_read(&mdsc->snap_rwsem);
 
-		if (snapc != (void *)page->private) {
+		if (snapc->seq > oldest->seq) {
+			ceph_put_snap_context(oldest);
 			dout(" page %p snapc %p not current or oldest\n",
-			     page, (void *)page->private);
+			     page, snapc);
 			/*
 			 * queue for writeback, and wait for snapc to
 			 * be writeable or written
 			 */
-			snapc = ceph_get_snap_context((void *)page->private);
+			snapc = ceph_get_snap_context(snapc);
 			unlock_page(page);
 			ceph_queue_writeback(inode);
-			wait_event_interruptible(ci->i_cap_wq,
+			r = wait_event_interruptible(ci->i_cap_wq,
 			       context_is_writeable_or_written(inode, snapc));
 			ceph_put_snap_context(snapc);
+			if (r == -ERESTARTSYS)
+				return r;
 			return -EAGAIN;
 		}
+		ceph_put_snap_context(oldest);
 
 		/* yay, writeable, do it now (without dropping page lock) */
 		dout(" page %p snapc %p not current, but oldest\n",
@@ -1035,7 +1040,7 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
 	int r;
 
 	do {
-		/* get a page*/
+		/* get a page */
 		page = grab_cache_page_write_begin(mapping, index, 0);
 		if (!page)
 			return -ENOMEM;